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Genus Aspiculophora Ruiz et al. 2017 Diagnosis: Plakinidae without spicules, well-developed mesohyl with a collagen layer between ecto- and choanosome, with or without sub-ectosomal cavities. Leuconoid aquiferous system and aphodal choanocyte chambers. High abundance of prokaryotic symbionts.

Aspiculortis garifuna sp. nov. Etymology: The genus name Aspiculortis refers to the absence of skeleton and to the genetic proximity of Plakortis. The species name garifuna honors the ethnical and cultural diversity of the Garifuna people, descendants of the first Caribs, Arawak Amerindians and the African people who inhabited the Lesser Antilles. Diagnosis: Thick crust (about 5 mm thick) with irregular form. No spicules, nor fibrous skeleton. The surface is covered by ostia with a series of translucent canals ending in prominent oscula of about 2 mm diameter. One type of vacuolar cell abounds in the ectosome and is also present in the mesohyl. Examined material: Holotype: Muséum National d’Histoire Naturelle de Paris, France MNHN DJV202 Martinique, “Grotte Fer à Cheval” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark section of the cave, date 25/03/2012, sample code: 120325 MT4 b-TP6, collector: T. Pérez. Genbank accession number: MK 949483 Paratype: Muséum National d’Histoire Naturelle de Paris, France MNHN DJV203 Guadeloupe, “Grotte aux Barracudas” (16°27.301’ N, 61°32.253’ W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 30/05/2015, sample code: 150530GU5-CR6, collector: C. Ruiz. Genbank accession number: MK 949485 Other material examined: Bequia, The Grenadines “Full Moon Cave” (12°59.525’ N, 61°16.731’ W), 10-12 m depth, beneath an overhang, date 19/05/2015, sample code: 150519LG1-CR14, collector: C. Ruiz. Genbank accession number: MK 949484 Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark section of the cave, date 11/06/2011, sample code: 110613 MT4 -TP3, collector: T. Pérez. Genbank accession number: MK 949482 Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 11/06/2011, sample code: 110613 MT4 -TP8, collector: T. Pérez. Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 15/05/2015, sample code: 150515 MT4 -CR1, collector: C. Ruiz. Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 16/05/2015, sample code: 160515 MT4 -CR9, collector: C. Ruiz. Comparative material examined: Aspiculophora madinina Ruiz, Muricy, Lage, Domingos, Chenesseau & Pérez 2017, Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark section of the cave, date 16/05/2015, sample code: 160515 MT4 -CR10, collector: C. Ruiz. Plakina nathaliae (Ereskovsky et al. 2014), Saint Martin, “Basses Espagnoles” (18°07.821’N, 63°00.270’W), 15 m depth, beneath an overhang, date 27/05/2015, sample code: 270515SN5-TP01, collector: T. Pérez. Oscarella zoranja Pérez & Ruiz, 2018, Martinique, Rocher du Diamant, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark section of the cave, date 16/05/2015, sample code: 150516 MT4 -CR05, collector: C. Ruiz. Oscarella filipoi Pérez & Ruiz, 2018, Saint Lucie, “Anse Chastenet reef” (13°51.848’ N, 61°04.729’ W), 15 m depth, beneath an overhang, date 22/05/2015, sample code: 150522SL1-CR05, collector: C. Ruiz. Description: External morphology: Aspiculortis garifuna sp. nov. has an encrusting irregular form and a brown color in vivo and after fixation in ethanol. The largest specimen recorded measured 10 cm in diameter. This sponge is quite fragile. The smooth surface is pseudo-criblate, that it is to say covered by numerous ostia diverging soon under the epidermal surface in various inhalant canals. The sponge surface also presents a series of larger translucent exhalant canals ending in prominent oscula of about 2 mm in diameter. This dense network can appear contracted in some specimens (Figure 2 A-B). Internal Anatomy: No spicule nor fibrous skeleton. The ectosome is 40-60 µm thick (Figure 2 C-D). The aquiferous system is leuconoid. Inhalant canals are 10-15 µm wide, running perpendicular to the surface. Choanocyte chambers (15-33 µm in diameter) are diplodal, spherical to ovoid (Figure 2E). The proportion between mesohyl and choanocyte chambers is greater than 1. Cytology: Choanocytes are cylindrical, 5 µm wide and 7 µm high. Their nucleus is spherical (2 µm diameter) in apical position, their cytoplasm usually contains osmiophilic inclusions and vacuoles of about 2-3 µm in diameter that often harbor phagocytized bacteria (Figure 3A). The exo- and endopinacocytes are flagellated and flattened (12- 19 µm long; 3-4 µm wide) with several vacuoles and osmiophilic inclusions. The external surfaces of the exo- and endopinacocytes are covered with a double-layer of 0.5 µm thick glycocalyx (Figure 3B). One type of vacuolar cell is found in abundance in the ectosome, and to a lesser extent in the mesohyl. This irregular shaped-cell, 10 x 20 µm in dimension, harbors 2-4 translucent vacuoles which are 3 to 8 µm in diameter (Figure 3C) and which often contain dense or loose heterogeneous material (Figure 3D). No archaeocyte was observed. There is a high abundance of prokaryotic symbionts in the mesohyl, with at least five dominant morphotypes randomly distributed throughout the mesohyl (Figure 3E). The first morphotype is an ovoid cell 2 - 4 µm long, 2.5 – 3 µm wide with a clear cytoplasm. The second morphotype has the same ovoid shape and size but has a denser cytoplasm. The third morphotype is an irregular cell shape which is 2 – 4 µm long and about 1 – 2.5 µm wide. The fourth morphotype is bean-shaped, 2.5 - 3 µm long and about 0.5 wide. The fifth morphotype is circular with a diameter of about 0.5 µm. Ecology: This new sponge has been collected in the Caribbean islands (Lesser Antilles) of Guadeloupe, Martinique and Bequia. In all sites, this sponge inhabits vertical walls and ceilings of dark marine caves, located at depths between 10 and 25 m, in syntopy with several other Homoscleromorpha species. No sign of predation was observed. Serpulidae worms live in close association and are often observed living among the new sponge species (Figure 2B). Taxonomic remarks: Aspiculortis garifuna gen. nov. sp. nov. has an encrusting form, as do most of the cave-dwelling Homoscleromorpha. It clearly belongs to a well-supported clade gathering Plakortis species, but its pseudo-criblate surface is unique, and thus has never been observed in Plakortis. The lack of cytological description of Caribbean Plakortis did not allow any comparison with the cells content of the new sponge. The absence of skeleton and this original pseudo-criblate surface justify the creation of a new genus. The new sponge also clearly differs from the other skeleton-less Plakinidae by its external morphology and internal organization, particularly the proportion between mesohyl and choanocyte chambers and the low abundance of symbiotic microorganisms in the thinly encrusting Plakina nathaliae, and the thick collagen layer found in the ectosome of the massive Aspiculophora madinina, as well as its aphodal choanocyte chambers.

Oscarella minka sp. nov. Etymology: From the Quechuan mink’a (minga), this species name honors the pre-Columbian tradition of communal work for social purposes. Diagnosis: Thin crust less than 3 mm thick. Smooth surface. Ectosome 25 to 50 µm thick, well-developed mesohyl. Two types of vacuolar cells, leuconoid aquiferous system with diplodal choanocyte chambers. High abundance of prokaryotic symbionts in the mesohyl. Examined material: Holotype: Muséum National d’Histoire Naturelle de Paris, France MNHN DJV206 La Martinique, “Grotte Fer à Cheval” (14°27.882’ N, 61°01.162 W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 25/03/2012, sample code: 120325 MT4 b-TP8, collector: T. Pérez. Genbank accession number: MK 949481 Paratype: Muséum National d’Histoire Naturelle de Paris, France MNHN DJV207 Bequia, The Grenadines, “Full Moon Cave” (12°59.525’ N, 61°16.731’ W), 10-12 m depth, beneath an overhang, date 19/05/2015, sample code: 150519LG1-CR9, collector: C. Ruiz. Genbank accession number: MK 949480 Other material examined: Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 13/06/2011, sample code: 110613 MT4 -TP4, collector: T. Pérez. GenBank accession number: MK 949478 Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 15/05/2015, sample code: 150515 MT4 - CR2, collector: C. Ruiz. Genbank accession number: MK 949479 Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 13/06/2011, sample code: 110613 MT4 -TP6, collector: T. Pérez. Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 16/05/2015, sample code: 150516 MT4 -CR11, collector: C. Ruiz. Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 16/05/2015, sample code: 150516 MT4 -CR16, collector: C. Ruiz. Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 16/05/2015, sample code: 150516 MT4 -CR17, collector: C. Ruiz. Bequia, The Grenadines, “Full Moon Cave” (12°59.525’ N, 61°16.731’ W), 10-12 m depth, beneath an overhang, date 28/04/2015, sample code: 150428LG1-AE55, collector: A. Ereskovsky. Bequia, The Grenadines, “Full Moon Cave” (12°59.525’ N, 61°16.731’ W), 10-12 m depth, beneath an overhang, date 19/05/2015, sample code: 150519LG1-TP5, collector: T. Pérez. Guadeloupe, “Grotte Cathédrale” (16°27.740’ N, 61°31.837’ W), 18 m depth, on a vertical wall in the dark part of the cave, date 29/05/2015, sample code: 150529GU3-TP2, collector: T. Pérez. Guadeloupe, “Grotte aux Barracudas” (16°27.301’ N, 61°32.253’ W), 19 m depth, beneath an overhang, date 30/05/2015, sample code: 150530GU5-CR4, collector: C. Ruiz. Guadeloupe, “Grotte aux Barracudas” (16°27.301’ N, 61°32.253’ W), 19 m depth, beneath an overhang, date 30/05/2015, sample code: 150530GU5-CR10, collector: C. Ruiz. Comparative material examined: Oscarella filipoi, Martinique, Anse d’Arlet, Grande Anse, Pointe Burgos - Grotte Couleur (14°2.787’N, 61°5.351’W), 10 m depth, on a vertical wall in semi-dark conditions, date 11/06/2011, sample code: 110611 MT3 -TP05, collector: T. Pérez. Oscarella zoranja, “ Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, date 13/06/2011, sample code: 110613 MT4 -TP1, collector: T. Pérez

Genus Oscarella Vosmaer, 1884 Diagnosis: Homosclerophorida without skeleton, with a variable development of the ectosome with a collagen layer between ecto- and choanosome. The aquiferous system has a sylleibid-like or leuconoid organization, with spherical to ovoid eurypilous or diplodal choanocyte chambers arranged around large exhalants canals (Muricy & Díaz 2002). Mitochondrial genomes that have been sequenced so far encode a gene absent in other animal mitochondrial genomes: tatC (Ereskovsky et al. 2017).

Aspiculophora papillata sp. nov. Etymology: the species name refers to the papillate surface of this Plakinidae, papilla = nipple in Latin. Diagnosis: encrusting Aspiculophora with papillate surface. Collagen layer ( Examined material: Holotype: Muséum National d’Histoire Naturelle de Paris, France MNHN DJV204 Bequia, The Grenadines, “Full Moon Cave” (12°59.525’ N, 61°16.731’ W), 10-12 m depth, beneath an overhang, date 19/05/2015, sample code: 150519LG1-CR13, collector: C. Ruiz. Genbank accession number: MK 949486 Paratype: Muséum National d’Histoire Naturelle de Paris, France MNHN DJV205 Guadeloupe, “Grotte Cathédrale” (16°27.740’ N, 61°31.837’ W), 18 m depth, on a vertical wall in the dark part of the cave, date 29/05/2015, sample code: 150529GU3-CR1, collector: C. Ruiz. Other material examined: Martinique, “Grotte Zeb” (14°27.832’N, 61°01.065’W), 19 m depth, on a vertical wall in the semi-dark part of the cave, dates 15 and 16/05/2015, sample codes: 150515 MT4 -CR3, 150515 MT4 - CR6, 160515 MT4 -CR14, collector: C. Ruiz. Bequia, The Grenadines “Full Moon Cave” (12°59.525’ N, 61°16.731’ W), 10-12 m depth, beneath an overhang, date 19/05/2015, sample codes: 150519LG1-CR10, 150519LG1-CR13, 150519LG1-TP11, collectors: C. Ruiz & T. Pérez Comparative material examined: Aspiculophora madinina MNHN DJV 180, Rocher du Diamant “Grotte Zeb”, Martinique (14°26.5´N, 61°03.083´W), 12 m depth, date 13/06/2011, sample code: 110613 MT4 -TP11 collector: T. Pérez, Aspiculophora madinina, “ Grotte Amédien”, Guadeloupe (16°30.033’ N, 061°28.774’ W), 12 m depth, date 30/05/2015, sample code: 150530-GU6-TP07, collector: T. Pérez. Plakina nathaliae MNHN DJV 179, Rocher du Diamant “Grotte Zeb”, La Martinique (14°26.5´N, 61°03.083´W), 17 m depth, date 13/06/2011, sample code: 110613 MT4 -TP2, collector: T. Pérez. Description: External morphology: Aspiculophora papillata sp. nov. is a thinly encrusting irregular sponge which is quite hard to collect because of its fragile consistency. Collected specimens measured up to 10 cm wide and 1 mm thick. The sponge has a papillate surface and its color varies from yellow to light brown in vivo, whereas it is light brown in ethanol. Papillae are cylindrical, up to 3 mm high and about 1 mm in diameter. The top of the papillae is often larger with an umbrella-like form of 2-3 mm in diameter. Oscula of about 1 mm in diameter are sometimes visible in the top of the papillae (Figure 4A, B). Internal Anatomy: No spicule or fibrous skeleton. A collagen lager Cytology: Choanocytes are cylindrical, 5 µm wide and 8 µm high. Their nuclei are spherical, about 2 µm in diameter and are located in apical position. Their cytoplasm usually contains osmiophilic inclusions of about 0.1 µm in diameter in basal position (Figure 5A, B). Apopylar cells have a trapezoid shape (Figure 5A). Exo- and endopinacocytes are flat and flagellated (5-15 µm long; 1-2 µm wide) with a nucleus of about 2.5 µm in diameter (Figure 5C). One type of abundant vacuolar cell was found randomly distributed in the mesohyl. This cell has an ovoid to spherical shape, is 12-20 µm in diameter, and generally harbors one to five vacuoles occupying most of the volume of the cytoplasm. Some heterogeneous to filamentous materials can be seen inside the vacuoles, and microorganisms can be found in their cytoplasm (see arrow in Figure 5C). No archaeocyte was observed. The new species can be considered as an HMA sponge. At least four prokaryotic morphotypes seem to be dominant in the mesohyl (Figure 5D). The first morphotype is peanut-shaped, 2.5 µm long 0.5 µm wide, with a dense cytoplasm and a double membrane. The second morphotype is of similar size, is cylindrical in shape and has a translucent external membrane. The third morphotype has an irregular shape and is 2-4 µm long and 1 µm wide. The fourth morphotype is bean-shaped with a dense membrane and translucent cytoplasm. Ecology: The new sponge species was found in the Caribbean islands of Guadeloupe, Martinique and Bequia (Lesser Antilles). It lives in sympatry (and sometimes in syntopy) with A. madinina, on walls and ceilings of dark marine caves, where it is always found between 10 and 20 m depth. No sign of predation was observed, but the new species usually lives in close association with other sponges and invertebrates such as Serpulidae and Sabellidae worms (Figure 4A). Taxonomic remarks: Aspiculophora papillata sp. nov. is a skeleton-less Plakinidae like A. madinina. The new species mainly differs by its external morphology, the papillate surface being a trait observed for the first time among Homoscleromorpha. In contrast with A madinina, no dark exudate was recorded in contact with alcohol for A. papillata. The collagen layer between the exopinacoderm and the ectosome region in A. papillata sp. nov. is very thin in comparison with A. madinina. Another difference between these species is the presence of sub-ectosomal cavities in A. papillata sp. nov. that do not exist in A. madinina. Both species share the leuconoid aquiferous system with aphodal choanocyte chambers, only one type of vacuolar cell which is mostly concentrated in the ectosome and similar microbial compositions.

Aspiculortis gen. nov. Diagnosis: Plakinidae without spicules. Smooth pseudo-criblate surface covered by numerous ostia diverging soon under the epidermal surface in various inhalant canals. A network of superficial translucent much larger exhalant canals leading to prominent oscula. Well-developed mesohyl with several layers of vacuolar cells in the ectosome. No sub-ectosomal cavities. Leuconoid aquiferous system with diplodal choanocyte chambers. High abundance of prokaryotic symbionts in the mesohyl.

Halisarca desqueyrouxae sp. nov. (Figs 11–18, Table 1) Material examined. Holotype: RBINS-IG 32236- POR. 10803 (Fragments: MNRJ 10803, MHNG 90139), Reñihue Fjord, Palena Province, Chile (42°31'55.02"S –72°35'30.72"'W), 3 m depth, coll. Ph. Willenz & E. Hajdu, 22.v. 2007. Paratypes: RBINS-IG 3 2235- POR. 10754 (Fragments: MNRJ 10754, MHNG 90094), Liliguapi Island, Comau Fjord, Palena Province, Chile (42°09’43.32”S – 72°35’54.90”W), 14 m depth, coll. Ph. Willenz & E. Hajdu, 07.v.2007. RBINS-IG 3 2236- POR. 10757 (Fragments: MNRJ 10757, MHNG 90097), Liliguapi Island, Comau Fjord, Palena Province, Chile (42°09’43.32”S – 72°35’54.90”W), 13 to 16 m depth, coll. Ph. Willenz & E. Hajdu, 07.v.2007. RBINS-IG 3 2238- POR. 12917 (Fragments: MNRJ 12917, MHNG 90251), Liliguapi Island, Comau Fjord, Palena Province, Chile (42°09'43.32"S – 72°35'54.90"W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. RBINS-IG 32238- POR. 1 2919 (Fragments: MNRJ 12919, MHNG 90253), Liliguapi Island, Comau Fjord, Palena Province, Chile (42°09'43.32"S – 72°35'54.90"W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. RBINS-IG 32238- POR. 12924 (Fragments: MNRJ 12924, MHNG 90258), Liliguapi Island, Comau Fjord, Palena Province, Chile (42°09'43.32"S – 72°35'54.90"W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. Additional paratypes not observed in Electron Microscopy. RBINS-IG 32 232- POR. 8795 (Fragment: MNRJ 8795) Liliguapi Island, Comau Fjord, Palena Province, Chile (42°09’44.23”S – 72°35’42.99”W), 20 m depth, coll. Ph. Willenz & E. Hajdu, 24.ii.2005. RBINS-IG 32236- POR. 9193 (Fragment: MNRJ 9193), Estero Farquhar, Bernardo Fjord, Capitán Prat Province, Chile (48˚29'18,70"S–74˚12'25,70"W), 4 m depth, coll. V. Häusssermann & G. Försterra, 29.iii.2005. RBINS-IG 32236- POR. 9214 (Fragments: MNRJ 9214, Estero Farquhar, Bernardo Fjord, Capitán Prat Province, Chile (48˚29'18,70"S–74˚12'25,70"W), 5 m depth, coll. V. Häusssermann & G. Försterra, 29.iii.2005. RBINS-IG 32236- POR. 9215 (Fragments: MNRJ 9215, Tempano Fjord, Capitán Prat Province, Chile (48°42'59.70"S – 74°00'18.80"W), 8 m depth, coll. V. Häusssermann & G. Försterra, 26.iii.2005. RBINS-IG 32233- POR. 9961 (Fragments: MNRJ 9961, MHNG 90662), Isla Lavinia, Última Esperanza Province, Chile (49°00'48.10"S – 74°58'37.50"W), 4 m depth, coll. Ph. Willenz & L. Atwood, 13.iii.2006. RBINS-IG 32 238- POR. 12923 (Fragments: MNRJ 12923, Liliguapi Island, Comau Fjord, Palena Province, Chile (42°09’44.23”S – 72°35’42.99”W), 11 m depth, coll. Ph. Willenz & J. Biro, 1.ii.2009. External morphology. Polymorphic sponge. The first morphotype corresponding to the holotype is the most frequently encountered. It consists of an encrusting wrinkled mat, up to 2 cm thick, composed of ridges and short digitations with well-defined oscula (morphotype 1, Figs 11 A–11D). The surface is slimy with clear and evenly spread ostia. The consistency is resistant to tearing. The second morphotype is represented by individuals of tubular form varying in length, with a single and sometimes stretched out osculum (morphotype 2, Figs 11 E–11H). Colour. Both morphotypes are light brown when exposed to the light and beige when hidden under overhangs. Anatomy. The ectosome varies from 80 to 250 µm in thickness (Figs 12 A, 12B, 12D, 12E & 12G–12H). On its outside, it is delimited by a superficial layer made of plane extensions of exopinacocytes connecting through thin processes with their cell bodies, which are located under a thick complex collagenous layer (Figs 13 B & 13C). No glycocalyx covers the external membrane of the exopinacocytes in any of the observed samples. A complex collagenous layer contains two distinct regions: its outward side has a loose and diffuse unorganized structure, 1 to 14 µm thick; its inward side, 3 to 5 µm thick, is made of collagen fibrils arranged in dense tracts, which are in contact with the underlying choanosome (Figs 13 A, 13C & 13E). The global thickness of the collagenous layer is not consistent and ranges between 6 to 19 µm among the samples, but without any particular widening. Spherulous cells are scattered in the collagenous layer and are abundantly concentrated in the ectosome. They are more dispersed in the choanosome (Figs 12 A– 12I). Symbiotic bacteria are also present from the outermost collagenous layer to the deepest regions of the mesohyl. The choanosome includes typical elongate and convoluted choanocyte chambers (50 to 260 µm long x 20 to 60 µm wide) surrounded by numerous aquiferous canals of various diameters (Figs 12 A– 12I). The mesohyl is very lax and remarkably clear, lacking dense granules (Figs 14–17), but contains collagen tracts (Figs 12 D–12F) and different wandering cell types at low density. Cytology. Exopinacocytes (Figs 13 A–13E) are "T-shaped" in transverse section. Their cell bodies (2.8 to 6.7 µm in diameter), with basal nucleolated nuclei, are deeply rooted under the complex collagenous layer, and connect with thin flake-like superficial extensions, revealed in SEM, through outstretched projections (Figs 13 A– 13C). Inter-cellular junctions between superficial extensions connect exopinacocytes to each other (Fig. 13 D). Choanocytes (Figs 14 A–14D) are stretched and cylindrical with a roughly pyramidal base (6.9 to 10.5 µm long x 2.1 to 8.3 µm wide) provided with basal pseudopods extending toward the mesohyl. The cytoplasm comprises electron dense inclusions and phagosomes, mainly concentrated on the basal side of the cell, and an apical nucleus. A periflagellar sleeve surrounds the base of the flagellum. Endopinacocytes (Figs 15 A & 15B) are flat with a prominent oval nucleus and constitute the walls of the canals. Basopinacocytes were not observed. Archaeocytes (Fig 16 A) are few and have a conventional amoeboid shape (6.2–8.0 µm) with a spherical nucleolated nucleus (3.7 to 4.3 µm in diameter). The cytoplasm is dense with phagosomes and vacuoles of different densities varying from 270 to 670 nm in diameter. Lophocytes (Figs 16 B & 16C) are elongated (ranging 2.3 x 9.6 µm) with tufts of collagen fibrils emerging from their posterior side or surrounding them. The nucleus is located in the anterior part of the cell. The cytoplasm is dense, contains phagosomes and small osmiophilic inclusions (330 x 730 nm). Spherulous cells of two different types are distinguished in TEM (Figs 13 A & 13C). Spherulous cells Type I (Figs 16 D & 17C) are oval cells (7.8–10.9 x 11.5–12.0 µm in diameter) with short pseudopodial extensions. Large dense osmiophilic homogeneous membrane-bound inclusions of variable diameter (1.0 to 3.8 µm) squeeze the central nucleolated nucleus, leaving exiguous space for a cytoplasm containing phagosomes and small electron translucent vesicles (100 to 200 nm). They are the most abundant cells in the mesohyl. Spherulous cells Type III (Figs 13 A, 16E–16G & 17F) are large cells (5.0–7.4 x 8.8–10.6 µm) with irregular shape. Large inclusions (0.8 to 2.0 µm in diameter) of porous texture with a denser periphery occupy most volume of the cytoplasm that contains large phagosomes, except for the cells occurring near the exopinacocytes (Fig. 16 G). These cells are common and mainly located in the upper part of the ectosome and occur less often in the choanosome; they are not found in all specimens examined (Table 1). Granular cells (Fig. 16 H) are round cells (4.5–7.0 x 6.7–7.7 µm in diameter) with homogeneous spherical inclusions of variable size and density (0.6–1.0 x 1.6–3.6 µm in diameter) and large phagosomes. These cells are found in the choanosome but do not occur in all specimens (Table 1). Rhabdiferous cells (Figs 17 A & 17B) are irregularly shaped cells (7.9–4.0 x 6.3–1.7 µm) with short pseudopodia. The nucleus is spherical and anucleolated (1.7–2.6 µm in diameter). The cytoplasm contains abundant osmiophilic elliptical membrane bound rhabdites (up to 1.3 µm in length and 0.8 µm in diameter), which include a less dense spherical sub-inclusion. Rhabdiferous cells occur in the ectosome and in the choanosome, where they are either free in the mesohyl or occasionally enclosed within choanocyte chambers and even larvae. Pocket cells (Figs 17 C–17H) are amoeboid cells (6.3–13.3 x 3.9–7.2 µm) with long pseudopods extending actively around the cell to phagocytize components of the mesohyl, including cells from other types and bacteria, forming large "pockets". The nucleolated nucleus is round to ovoid (2.9 to 4.0 x 2.6 to 3.5 µm). These cells occur everywhere in the sponge, from the choanosome to the ectosome where they appear to be more developed. Their membrane is folded in many thin and puffed layers, forming small electron translucent microvesicles located at the periphery of the cell. Some pocket cells with numerous pockets and smaller electron translucent vacuoles are crossing the collagen layer to be rejected from the sponge as they are found at the surface of the exopinacocytes. Extracellular symbiotic bacteria (Figs 18 A–18E) of three different morphotypes occur in the mesohyl. The nomenclature used here corresponds to the one used above for H. magellanica. Type B1 is absent. Type B2 is rod shaped and reaches 1.9 µm in length and 0.3 µm in diameter with an electron dense thick wall and an electron translucent cytoplasmic matrix. The electron translucent nucleoid presents a central rod surrounded by filamentous material. Type B2 occurs only in H. desqueyrouxae sp. nov. morphotype 2 (Table 1). Type B3 is spiral-shaped and thick walled, its width reaches 0.4 to 0.5 µm. The cytoplasmic matrix is clear and the nucleoid is electron dense. Type B3 occurs in the choanosome of all specimens of both morphotypes where it is evenly distributed. Type B4 is larger in diameter than Type B2 (1.1 to 1.4 x 0.5 µm), and has a more ovoid shape and a wrinkled capsule. No central rod appears in the clear nucleoid. This type was found in only one specimen of each morphotype (Table 1). Types B2 and B4 are exclusively found in the collagenous layer of the ectosome where they are frequent. Reproduction. One of the three specimens collected in early February 2009 contained embryos and prelarvae. Larvae appeared in two out of the three specimens collected in May 2007 (Figs 12 A, 12C & 12H). Distribution. Halisarca desqueyrouxae sp. nov. is presently known from Chilean Patagonia (42°S). Habitat. Halisarca desqueyrouxae sp. nov. is commonly found at depths ranging from 3 to 26 m, on mussel beds at shallow depths or covering rocks exposed to the light and under overhangs below 10 m. Etymology. The specific epithet is a tribute to Dr. Ruth Desqueyroux-Faúndez who inspired our first sponge collections in Chilean Patagonia and actively participated in several expeditions in that region. Phylogenetic analysis. Partial cox1 sequences were determined for seven specimens of H. desqueyrouxae sp. nov. (RBINS 10803, 10757, 12917, 12919, 12924 and 12923 = morphotype 1; RBINS 10754 = morphotype 2) and were found to be identical. Phylogenetic analysis placed H. desqueyrouxae sp. nov. as a sister group to H. dujardini, but revealed 2.3% difference between their cox1 sequences (Fig. 19).

Halisarca desqueyrouxae sp. nov. (Figs 11���18, Table 1) Material examined. Holotype: RBINS-IG 32236- POR. 10803 (Fragments: MNRJ 10803, MHNG 90139), Re��ihue Fjord, Palena Province, Chile (42��31'55.02"S ���72��35'30.72"'W), 3 m depth, coll. Ph. Willenz & E. Hajdu, 22.v. 2007. Paratypes: RBINS-IG 3 2235- POR. 10754 (Fragments: MNRJ 10754, MHNG 90094), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���43.32���S ��� 72��35���54.90���W), 14 m depth, coll. Ph. Willenz & E. Hajdu, 07.v.2007. RBINS-IG 3 2236- POR. 10757 (Fragments: MNRJ 10757, MHNG 90097), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���43.32���S ��� 72��35���54.90���W), 13 to 16 m depth, coll. Ph. Willenz & E. Hajdu, 07.v.2007. RBINS-IG 3 2238- POR. 12917 (Fragments: MNRJ 12917, MHNG 90251), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09'43.32"S ��� 72��35'54.90"W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. RBINS-IG 32238- POR. 1 2919 (Fragments: MNRJ 12919, MHNG 90253), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09'43.32"S ��� 72��35'54.90"W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. RBINS-IG 32238- POR. 12924 (Fragments: MNRJ 12924, MHNG 90258), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09'43.32"S ��� 72��35'54.90"W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. Additional paratypes not observed in Electron Microscopy. RBINS-IG 32 232- POR. 8795 (Fragment: MNRJ 8795) Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���44.23���S ��� 72��35���42.99���W), 20 m depth, coll. Ph. Willenz & E. Hajdu, 24.ii.2005. RBINS-IG 32236- POR. 9193 (Fragment: MNRJ 9193), Estero Farquhar, Bernardo Fjord, Capit��n Prat Province, Chile (48˚29'18,70"S���74˚12'25,70"W), 4 m depth, coll. V. H��usssermann & G. F��rsterra, 29.iii.2005. RBINS-IG 32236- POR. 9214 (Fragments: MNRJ 9214, Estero Farquhar, Bernardo Fjord, Capit��n Prat Province, Chile (48˚29'18,70"S���74˚12'25,70"W), 5 m depth, coll. V. H��usssermann & G. F��rsterra, 29.iii.2005. RBINS-IG 32236- POR. 9215 (Fragments: MNRJ 9215, Tempano Fjord, Capit��n Prat Province, Chile (48��42'59.70"S ��� 74��00'18.80"W), 8 m depth, coll. V. H��usssermann & G. F��rsterra, 26.iii.2005. RBINS-IG 32233- POR. 9961 (Fragments: MNRJ 9961, MHNG 90662), Isla Lavinia, ��ltima Esperanza Province, Chile (49��00'48.10"S ��� 74��58'37.50"W), 4 m depth, coll. Ph. Willenz & L. Atwood, 13.iii.2006. RBINS-IG 32 238- POR. 12923 (Fragments: MNRJ 12923, Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���44.23���S ��� 72��35���42.99���W), 11 m depth, coll. Ph. Willenz & J. Biro, 1.ii.2009. External morphology. Polymorphic sponge. The first morphotype corresponding to the holotype is the most frequently encountered. It consists of an encrusting wrinkled mat, up to 2 cm thick, composed of ridges and short digitations with well-defined oscula (morphotype 1, Figs 11 A���11D). The surface is slimy with clear and evenly spread ostia. The consistency is resistant to tearing. The second morphotype is represented by individuals of tubular form varying in length, with a single and sometimes stretched out osculum (morphotype 2, Figs 11 E���11H). Colour. Both morphotypes are light brown when exposed to the light and beige when hidden under overhangs. Anatomy. The ectosome varies from 80 to 250 ��m in thickness (Figs 12 A, 12B, 12D, 12E & 12G���12H). On its outside, it is delimited by a superficial layer made of plane extensions of exopinacocytes connecting through thin processes with their cell bodies, which are located under a thick complex collagenous layer (Figs 13 B & 13C). No glycocalyx covers the external membrane of the exopinacocytes in any of the observed samples. A complex collagenous layer contains two distinct regions: its outward side has a loose and diffuse unorganized structure, 1 to 14 ��m thick; its inward side, 3 to 5 ��m thick, is made of collagen fibrils arranged in dense tracts, which are in contact with the underlying choanosome (Figs 13 A, 13C & 13E). The global thickness of the collagenous layer is not consistent and ranges between 6 to 19 ��m among the samples, but without any particular widening. Spherulous cells are scattered in the collagenous layer and are abundantly concentrated in the ectosome. They are more dispersed in the choanosome (Figs 12 A��� 12I). Symbiotic bacteria are also present from the outermost collagenous layer to the deepest regions of the mesohyl. The choanosome includes typical elongate and convoluted choanocyte chambers (50 to 260 ��m long x 20 to 60 ��m wide) surrounded by numerous aquiferous canals of various diameters (Figs 12 A��� 12I). The mesohyl is very lax and remarkably clear, lacking dense granules (Figs 14���17), but contains collagen tracts (Figs 12 D���12F) and different wandering cell types at low density. Cytology. Exopinacocytes (Figs 13 A���13E) are "T-shaped" in transverse section. Their cell bodies (2.8 to 6.7 ��m in diameter), with basal nucleolated nuclei, are deeply rooted under the complex collagenous layer, and connect with thin flake-like superficial extensions, revealed in SEM, through outstretched projections (Figs 13 A��� 13C). Inter-cellular junctions between superficial extensions connect exopinacocytes to each other (Fig. 13 D). Choanocytes (Figs 14 A���14D) are stretched and cylindrical with a roughly pyramidal base (6.9 to 10.5 ��m long x 2.1 to 8.3 ��m wide) provided with basal pseudopods extending toward the mesohyl. The cytoplasm comprises electron dense inclusions and phagosomes, mainly concentrated on the basal side of the cell, and an apical nucleus. A periflagellar sleeve surrounds the base of the flagellum. Endopinacocytes (Figs 15 A & 15B) are flat with a prominent oval nucleus and constitute the walls of the canals. Basopinacocytes were not observed. Archaeocytes (Fig 16 A) are few and have a conventional amoeboid shape (6.2���8.0 ��m) with a spherical nucleolated nucleus (3.7 to 4.3 ��m in diameter). The cytoplasm is dense with phagosomes and vacuoles of different densities varying from 270 to 670 nm in diameter. Lophocytes (Figs 16 B & 16C) are elongated (ranging 2.3 x 9.6 ��m) with tufts of collagen fibrils emerging from their posterior side or surrounding them. The nucleus is located in the anterior part of the cell. The cytoplasm is dense, contains phagosomes and small osmiophilic inclusions (330 x 730 nm). Spherulous cells of two different types are distinguished in TEM (Figs 13 A & 13C). Spherulous cells Type I (Figs 16 D & 17C) are oval cells (7.8���10.9 x 11.5���12.0 ��m in diameter) with short pseudopodial extensions. Large dense osmiophilic homogeneous membrane-bound inclusions of variable diameter (1.0 to 3.8 ��m) squeeze the central nucleolated nucleus, leaving exiguous space for a cytoplasm containing phagosomes and small electron translucent vesicles (100 to 200 nm). They are the most abundant cells in the mesohyl. Spherulous cells Type III (Figs 13 A, 16E���16G & 17F) are large cells (5.0���7.4 x 8.8���10.6 ��m) with irregular shape. Large inclusions (0.8 to 2.0 ��m in diameter) of porous texture with a denser periphery occupy most volume of the cytoplasm that contains large phagosomes, except for the cells occurring near the exopinacocytes (Fig. 16 G). These cells are common and mainly located in the upper part of the ectosome and occur less often in the choanosome; they are not found in all specimens examined (Table 1). Granular cells (Fig. 16 H) are round cells (4.5���7.0 x 6.7���7.7 ��m in diameter) with homogeneous spherical inclusions of variable size and density (0.6���1.0 x 1.6���3.6 ��m in diameter) and large phagosomes. These cells are found in the choanosome but do not occur in all specimens (Table 1). Rhabdiferous cells (Figs 17 A & 17B) are irregularly shaped cells (7.9���4.0 x 6.3���1.7 ��m) with short pseudopodia. The nucleus is spherical and anucleolated (1.7���2.6 ��m in diameter). The cytoplasm contains abundant osmiophilic elliptical membrane bound rhabdites (up to 1.3 ��m in length and 0.8 ��m in diameter), which include a less dense spherical sub-inclusion. Rhabdiferous cells occur in the ectosome and in the choanosome, where they are either free in the mesohyl or occasionally enclosed within choanocyte chambers and even larvae. Pocket cells (Figs 17 C���17H) are amoeboid cells (6.3���13.3 x 3.9���7.2 ��m) with long pseudopods extending actively around the cell to phagocytize components of the mesohyl, including cells from other types and bacteria, forming large "pockets". The nucleolated nucleus is round to ovoid (2.9 to 4.0 x 2.6 to 3.5 ��m). These cells occur everywhere in the sponge, from the choanosome to the ectosome where they appear to be more developed. Their membrane is folded in many thin and puffed layers, forming small electron translucent microvesicles located at the periphery of the cell. Some pocket cells with numerous pockets and smaller electron translucent vacuoles are crossing the collagen layer to be rejected from the sponge as they are found at the surface of the exopinacocytes. Extracellular symbiotic bacteria (Figs 18 A���18E) of three different morphotypes occur in the mesohyl. The nomenclature used here corresponds to the one used above for H. magellanica. Type B1 is absent. Type B2 is rod shaped and reaches 1.9 ��m in length and 0.3 ��m in diameter with an electron dense thick wall and an electron translucent cytoplasmic matrix. The electron translucent nucleoid presents a central rod surrounded by filamentous material. Type B2 occurs only in H. desqueyrouxae sp. nov. morphotype 2 (Table 1). Type B3 is spiral-shaped and thick walled, its width reaches 0.4 to 0.5 ��m. The cytoplasmic matrix is clear and the nucleoid is electron dense. Type B3 occurs in the choanosome of all specimens of both morphotypes where it is evenly distributed. Type B4 is larger in diameter than Type B2 (1.1 to 1.4 x 0.5 ��m), and has a more ovoid shape and a wrinkled capsule. No central rod appears in the clear nucleoid. This type was found in only one specimen of each morphotype (Table 1). Types B2 and B4 are exclusively found in the collagenous layer of the ectosome where they are frequent. Reproduction. One of the three specimens collected in early February 2009 contained embryos and prelarvae. Larvae appeared in two out of the three specimens collected in May 2007 (Figs 12 A, 12C & 12H). Distribution. Halisarca desqueyrouxae sp. nov. is presently known from Chilean Patagonia (42��S). Habitat. Halisarca desqueyrouxae sp. nov. is commonly found at depths ranging from 3 to 26 m, on mussel beds at shallow depths or covering rocks exposed to the light and under overhangs below 10 m. Etymology. The specific epithet is a tribute to Dr. Ruth Desqueyroux-Fa��ndez who inspired our first sponge collections in Chilean Patagonia and actively participated in several expeditions in that region. Phylogenetic analysis. Partial cox1 sequences were determined for seven specimens of H. desqueyrouxae sp. nov. (RBINS 10803, 10757, 12917, 12919, 12924 and 12923 = morphotype 1; RBINS 10754 = morphotype 2) and were found to be identical. Phylogenetic analysis placed H. desqueyrouxae sp. nov. as a sister group to H. dujardini, but revealed 2.3% difference between their cox1 sequences (Fig. 19)., Published as part of Willenz, Philippe, Ereskovsky, Alexander V. & Lavrov, Dennis V., 2016, Integrative taxonomic re-description of Halisarca magellanica and description of a new species of Halisarca (Porifera, Demospongiae) from Chilean Patagonia, pp. 501-533 in Zootaxa 4208 (6) on pages 515-524, DOI: 10.11646/zootaxa.4208.6.1, http://zenodo.org/record/214957

Genus Halisarca Johnston, 1842 Diagnosis. Chondrillida in which the choanocyte chambers are tubular, branched and wide mouthed. Larvae are incubated disphaerulae (a larval form found only in Halisarca) with simple undifferentiated histology and cilia of uniform length. Skeleton is composed of fibrillar collagen only, there are no fibrous or mineral elements present; ectosomal and subectosomal collagen is highly organised and structurally diversified (Ereskovsky et al. 2011)., Published as part of Willenz, Philippe, Ereskovsky, Alexander V. & Lavrov, Dennis V., 2016, Integrative taxonomic re-description of Halisarca magellanica and description of a new species of Halisarca (Porifera, Demospongiae) from Chilean Patagonia, pp. 501-533 in Zootaxa 4208 (6) on page 503, DOI: 10.11646/zootaxa.4208.6.1, http://zenodo.org/record/214957, {"references":["Johnston, G. (1842) A History of British Sponges and Lithophytes. In. Lizars, W. H., Edinburgh, pp. i - xii, 1 - 264, pls I - XXV. http: // dx. doi. org / 10.5962 / bhl. title. 51495","Ereskovsky, A. V., Lavrov, D. V., Boury-Esnault, N. & Vacelet, J. (2011) Molecular and morphological description of a new species of Halisarca (Demospongiae: Halisarcida) from Mediterranean Sea and a redescription of the type species Halisarca dujardini. Zootaxa, 2768, 5 - 31."]}

Re-description of Halisarca magellanica Topsent, 1901 type species (Figs 2���10, Table 1) Synonymy. Halisarca dujardini var. magellanica, Topsent, 1901; Thiele, 1905; Burton, 1929, 1932, 1940. Original description. Halisarca dujardini var. magellanica, Topsent, 1901, p. 44���45. Type material. Holotype: RBINS-POR.034���4 fragments (alcohol), Antarctic Expedition of the Belgica 1897���99, sample n��47, Torrent Bay, Londonderry Island, Ant��rtica Chilena Province, Chile (55��03'S ��� 69��23'W), intertidal, coll. M. Racovitza, 18.xii.1897. Material examined. RBINS-IG 32232- POR. 8798 (Fragment: MNRJ 8798), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���44.23���S ��� 72��35���42.99���W), 20 m depth, coll. Ph. Willenz & E. Hajdu, 24.ii.2005. RBINS-IG 3 2232 - POR. 8888 (Fragments: MNRJ 8888, MHNG 89996), Piedra Lile, Quell��n, Chiloe Province, Chile (43��10���58.60���S ��� 73��38���27.20���W), 16 m depth, coll. E. Hajdu & Ph. Willenz, 04.iii.2005. RBINS-IG 32235 - POR. 10753 (Fragments: MNRJ 10753, MHNG 90093), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���44.23���S ��� 72��35���42.99���W), 13 m depth, coll. Ph. Willenz & E. Hajdu, 07.v.2007. RBINS-IG 32 235- POR. 10827 (Fragments: MNRJ 10827, MHNG 90161), Re��ihu�� Fjord, Palena Province, Chile (42��30'48.06"S ��� 72��37'49.74"W), 13 m depth, coll. Ph. Willenz & E. Hajdu, 23.v.2007. RBINS-IG 32238- POR. 12918 (Fragments: MNRJ 12918, MHNG 90252), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09'43.32"S ���72��35' 54.90W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. RBINS-IG 32238- POR. 12920 (Fragments: MNRJ 12920, MHNG 90254), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09'43.32"S ���72��35' 54.90W), 26 m depth, coll. Ph. Willenz & J. Biro, 01.ii.2009. RBINS-IG 32238- POR. 12921 (Fragments: MNRJ 12921, MHNG 90255), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���44.23���S ��� 72��35���42.99���W), 10 m depth, coll. Ph. Willenz, 01.ii.2009. RBINS-IG 32238- POR.12922 (Fragments: MNRJ 12922, MHNG 90256), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���44.23���S ��� 72��35���42.99���W), 10 m depth, coll. Ph. Willenz, 01.ii.2009. Additional material not observed in Electron Microscopy. MNRJ 8797 (Fragment: RBINS-IG 32232- POR. 8797), Liliguapi Island, Comau Fjord, Palena Province, Chile (42��09���44.23���S ��� 72��35���42.99���W), 20 m depth, coll. Ph. Willenz & E. Hajdu, 24.ii.2005. MNRJ 8892 (Fragment: RBINS-IG 32232- POR. 8892), Piedra Lile, Quell��n, Chiloe Province, Chile (43��10���58.60���S ��� 73��38���27.20���W), 16 m depth, coll. E. Hajdu & Ph. Willenz, 04.iii.2005. RBINS-IG 32238 - POR. 12933 (Fragment: MNRJ 12933), Re��ihu�� Fjord, Palena Province, Chile (42��30���20.70���S ��� 72��46���29.70���W), 30 m depth, coll. Ph. Willenz & J. Biro, 08.ii.2009. External morphology. Polymorphic sponge. The first morphotype, 0.2 to 10 mm thick, corresponding to the type specimen (Topsent 1901), is encrusting and massive with a slimy surface, slippery to the touch (morphotype 1, Figs 2 A���2D). The consistency is gelatinous and elastic. When growing on mussel banks or under overhangs, it forms stretched filamentous outgrowths of different lengths and shapes "dripping" downward, resulting in propagules bearing a discrete osculum at their end (Figs 2 A���2C). Ostia are microscopic and barely visible. The second morphotype is thinly encrusting, without propagules but with the same viscous surface and consistency (morphotype 2, Fig. 2 E). Both morphotypes are found on vertical to horizontal hard substrates or under overhangs. The third morphotype is "bushy", 1 to 5 cm high, made of grouped digitations, each with obvious pores (ostia) and always ending with a clearly visible osculum. The surface is velvety and the consistency is more brittle and less elastic than morphotypes 1 & 2. It is found growing mainly on vertical substrates (morphotype 3, Figs 2 F & 2G). Colour. All three morphotypes are bright pink when exposed to the light and usually ivory or whitish when hidden under overhangs. Anatomy. The ectosome has a thickness varying from 80 to 280 ��m in morphotypes 1 & 3 and reaches 900 ��m in morphotype 2 (Figs 3 A��� 3I). The structure of the ectosome is similar in all three morphotypes and is composed of a superficial layer made of flat extensions of exopinacocyte cell bodies, which themselves are located under an intermediary complex collagenous layer and connect to the surface of the sponge by thin processes (Figs 4 A���4C, 4E & 4F). Exopinacocyte cell bodies are distant from each other and are only tightly joined at the level of their superficial extensions. The external membrane of the exopinacocytes is covered by a thin glycocalyx varying from 30 to 150 nm (Fig. 4 F). The collagenous layer shows two regions: its outward side consists of a loose and diffuse unorganized structure 1 to 6 ��m thick, whereas its inward side consists of interlaced collagen fibrils forming dense tracts 2 to 25 ��m, which are in contact with the rest of the ectoderm lying underneath (Figs 4 C &4D). The thickness of the collagenous layer ranges from 4 ��m to 30 ��m with varying internal composition. In the arborescent morphotype, regularly spaced invaginations of the basal region of the collagenous layer extend into the mesohyl (Figs 3 I & 4B). Both regions of the collagenous layer include few scattered spherulous cells and bacteria (Figs 3 C & 3I, 4A & 4B). The choanosome is typical of all Halisarca species previously described in the literature, with irregularly shaped, elongated and curved choanocyte chambers (30 to 180 ��m long x 10 to 40 ��m wide), aquiferous canals and a mesohyl containing a variety of cell types, bacteria and collagen bundles (Figs 3 A���3C, 3E��� 3I & 5A). No difference in abundance or size of choanocyte chambers is observed between morphotypes 1 & 3 (Figs 3 B, 3C & 3F���3H). Chambers are less abundant in morphotype 2 (MNRJ 10753) and occur deeper in the sponge, under a 900 ��m thick ectosome (Fig 3 D). In some sections, choanocyte chambers are located radially around several thin, probably inhalant, canals 4 to 16 ��m in diameter (Fig 3 F). Larger canals, most likely exhalant, occur less frequently in the choanosome (Figs 3 A & 3D). In semi-thin sections stained with methylene blue/azure II and basic fuchsine, the mesohyl stains pink to purplish-red, indicating the abundance of collagen. TEM sections reveal the granular structure of the mesohyl; abundant electron dense granules 19 to 93 nm in diameter amalgamate in a fuzzy loose matrix crossed by collagen fibrils and bundles (Figs 7 D, 9A, 10D & 10G). Cytology. Exopinacocytes (Figs 4 A���4C, 4E & 4F) are "T-shaped" in transverse sections with an extremely thin superficial extension situated at the tip of a narrow projection emerging from the cell body and connecting cells to each other through inter-cellular junctions (Figs 4 E & 4F). Cell bodies (2.5 to 8.6 ��m in diameter), with a basal nucleolated nucleus, are anchored in the mesohyl below the complex collagen layer of the ectosome. Choanocytes (Figs 5 A���5E) are long and cylindrical (10.5���14.5 ��m x 4.0���4.5 ��m), with abundant basal pseudopodial extensions. The cytoplasm contains many electron translucent vacuoles, abundant larger electron dense basal inclusions and an apical nucleolated nucleus. An irregular periflagellar sleeve, sometimes longer than the microvilli of the collar, surrounds the base of the flagellum. Endopinacocytes (Figs 6 A���6C) are flat cells lining the canals of the aquiferous system. Their shape is thin and flat with a central oval nucleolated nucleus. Basopinacocytes were not observed. Archaeocytes (Fig. 7 A) are around 7.0 to 15.0 ��m in size, occur infrequently throughout the mesohyl and have a classical amoeboid shape with pseudopodia. The nucleolated nucleus (3.2 to 3.9 ��m in diameter) is spherical and located centrally. The cytoplasm is dense with phagosomes and electron-dense vacuoles of variable sizes ranging from 150 to 470 nm. Lophocytes (Figs 7 B���7D) are abundant elongated cells (around 1.5 x 14.0 ��m) with a tuft of collagen fibrils emerging from their posterior end. The nucleus is either located in the anterior (Fig. 7 B) or the posterior (Fig. 7 C) side of the cell. The cytoplasm is dense, contains phagosomes and small electron-dense inclusions (140 to 960 nm). Spherulous cells are of three types, two of which were never previously described in Halisarca. Spherulous cells Type I (Fig. 7 E) are globular oval cells (6.5���8.2 x 9.0���10.6 ��m in diameter) packed with large dense osmiophilic homogeneous membrane bound inclusions of variable diameter (1.1 to 4.8 ��m) squeezing a central nucleolated nucleus, and a relatively small remaining cytoplasmic volume. They are the most abundant mesohylar cells in the ectosome and the choanosome of all investigated specimens. Spherulous cells Type II (Fig. 7 F) are large, bulbous and spherical (7.8��� 8.9 x 7.8���11.6 ��m in diameter) with large inclusions of variable diameter (1.3 to 4.2 ��m) composed of two distinct parts: a large crescent-shaped osmiophilic portion encompasses a smaller elliptical less osmiophilic region, giving a "chestnut aspect" to these inclusions. The cytoplasm volume is also minimized and the central nucleus is nucleolated. These cells do not occur in all specimens but, when present, are common in the choanosome (Table 1). Spherulous cells Type III (Fig. 7 G) are more spherical (5.8���9.4 x 7.1���11.7 ��m) than the two previous types and contain heterogeneous inclusions (1.1���2.1 x 2.2���3.3 ��m) characterized by a rough internal texture with a more osmiophilic periphery. The cytoplasm volume is larger than in Type I and Type II, with a spherical nucleolated nucleus. These cells are rare, found only in the choanosome and are not observed in all specimens (Table 1). Granular cells (Fig. 7 H) are oval shaped cells (5.5��� 63 x 7.1���11.3 ��m) with a nucleolated nucleus and spherical homogeneous osmiophilic inclusions of variable size, but smaller than in spherulous cells Type 1 (0.6 x 1.6���2.3 ��m in diameter). These cells are infrequent, occur only in the choanosome and are not present in all specimens (Table 1). Microgranular cells (Fig. 8 A) are amoeboid cells (7.5���10.6 x 4.2���7.5 ��m), distinct from granular cells by their anucleolated nucleus and the abundance of electron dense spherical or elliptical inclusions of smaller size (0.5���0.8 x 0.2 ��m) contained in the cytoplasm. Small phagosomes and a developed endoplasmic reticulum are also present. Microgranular cells occur in all specimens examined but are not abundant, and are found randomly in the choanosome. Rhabdiferous cells (Figs 8 B���8E) are amoeboid in shape (4.5���10.7 x 3.3���7.6 ��m) with short pseudopodia. The nucleolated nucleus is relatively large and spherical (2.1���3.6 ��m in diameter). The cytoplasm is filled with osmiophilic elliptical membrane bound inclusions (0.7���1.7 x 0.4���0.7 ��m), which include one or two less dense spherical sub-inclusions (rhabdites). Rhabdiferous cells are numerous in all specimens examined and occur equally in the ectosome and the choanosome where they are even occasionally found within choanocyte chambers (Figs 8 D & 8E). Pocket cells (Figs 9 A���9G) are amoeboid in shape, of variable size, (6.3���8.8 x 8.9���16.9 ��m) characterized by one or several large "pockets" formed by junction of long and thin pseudopodial extensions engulfing portions of the mesohyl that often include bacteria. As the size and the number of pockets progressively increase, the volume of the cytoplasm decreases until it becomes a thin layer surrounding a nucleolated nucleus (1.7���2.1 x 2.2���3.3 ��m). The final content of the pockets has the same density as the mesohyl. The cytoplasm contains phagosomes and abundant electron dense and electron translucent small inclusions. Bacteriocytes (Figs 10 A���10C) are roundish massive cells (10.0���18.3 ��m in diameter) with pseudopodial extensions and packed with large bacteria of a single morphotype (Type B1). The cytoplasm is dense and the anucleolated nucleus is squeezed at the periphery of the cell. Bacteria are rod-shaped up to 4.5 ��m long and 1.2 ��m wide and are isolated from the cytoplasm by a membrane. All present a thick electron dense cytoplasm with a thin central electron translucent filamentous nucleoid. Bacteriocytes do not occur in all specimens, are infrequent and appear randomly in the choanosome. Extracellular symbiotic bacteria (Figs 10 D���10F). Two other morphotypes of bacteria are found extracellularly, evenly distributed in the mesohyl, spanning from the outward collagenous layer of the ectosome to the entire choanosome (Types B2 and B3). Type B2 is abundant, rod-shaped and reaches 910 nm in length and 380 nm in diameter. The cytoplasmic matrix is homogeneous and electron dense. The nucleoid is more electron translucent, with a central rod surrounded by filamentous material. The cell wall is thick and covered with discrete fimbriae. Type B3 is spiral-shaped and has a thick cell wall. The length is undetermined in TEM since an entire longitudinal section is unlikely obtained. The width ranges 200 to 470 nm. The cytoplasmic matrix is clear and the nucleoid is homogeneous and electron dense. Type B3 is much less frequent, occurs in a minority of specimens and is found exclusively in the choanosome (Table 1). Reproduction. One of both specimens collected in March 2005 and two out of four collected in February 2009 contained oocytes in different stages of development. Distribution. Halisarca magellanica is known from austral Chile (56�����54��S), Argentina and Uruguay (56����� 34��S) and Malvinas Islands (Desqueyroux & Moyano 1987). Habitat. Halisarca magellanica is commonly found at depths ranging from 1 to 26 m, on mussels beds at shallow depths or covering rocks below 10 m. Phylogenetic analysis. Partial cox1 sequences were determined for five specimens of H. magellanica (RBINS 10827 = morphotype 1; RBINS 10753 = morphotype 2; RBINS 12918, 12920 and 12921 = morphotype 3) and were found to be identical. Phylogenetic analysis of these data along with previously published sequences of H. dujardini, H. caerulea, H. harmelini, Halisarca sp. GW3298 from the Red Sea and selected outgroups showed H. magellanica forming a sister group to all other analysed Halisarca sequences except for H. harmelini (Fig. 19). The cox1 sequence of H. magellanica was 9.1���9.7% different from the other Halisarca species., Published as part of Willenz, Philippe, Ereskovsky, Alexander V. & Lavrov, Dennis V., 2016, Integrative taxonomic re-description of Halisarca magellanica and description of a new species of Halisarca (Porifera, Demospongiae) from Chilean Patagonia, pp. 501-533 in Zootaxa 4208 (6) on pages 503-515, DOI: 10.11646/zootaxa.4208.6.1, http://zenodo.org/record/214957, {"references":["Topsent, E. (1901) Spongiaires. Resultats du voyage du S. Y. Belgica en 1897 - 99 sous le commandement de A. de Gerlache de Gomery. Expedition antarctique belge. Zoologie, 4, 1 - 54.","Thiele, J. (1905) Die Kiesel- und Hornschwamme der Sammlung Plate. Supplement 6 (Fauna Chiliensis III). Zoologische Jahrbucher, 1905, 407 - 496, pls 427 - 433.","Burton, M. (1929) Porifera. Part II. Antarctic sponges. British Antarctic (\" Terra Nova \") Expedition, 1910. Natural History Report. London, British Museum (Natural History). Zoology, 6, 393 - 458, pls I - V.","Burton, M. (1932) Sponges. Discovery Reports, pp. 237 - 392, pls 248 - 257. http: // dx. doi. org / 10.5962 / bhl. part. 24379","Desqueyroux, R. & Moyano, H. (1987) Zoogeografia de Demospongias Chilenas-Zoogeography of Chilean Demospongiae. Boletin de la Sociedad de Biologia de Concepcion, 58, 39 - 66."]}

Redescription of Halisarca dujardini type species (Figs. 2���23) Previous reviews. L��vi 1956; Bergquist 1996; Bergquist & Cook 2002. Halisarca dujardini Johnston, 1842 Synonymy. Halisarca dujardini Johnston, 1842: 192���193; Lendenfeld 1889: 729���730; de Laubenfels 1948: 175���176; L��vi 1956: 184; Chen 1976: 113���139; Ereskovsky 1993: 8; Bergquist 1996: 24���27; Bergquist & Cook 2002: 1090���1091. Halisarca franz-schulzei Merejkowsky 1878: 27���36, Pl. I, fig. 1���6; Pl. II, fig. 9���15. Hymeniacidon dujardini Bowerbank 1866: 224. Halisarca sputum Topsent 1893: 38 ���39. Original description. Halisarca dujardini, Johnston, 1842, p. 192. Type material. Holotype: presumably lost. Neotype: BMNH 1960.1.7.1���Black Rock, Brighton, English Channel (epizootic on algae, collected close to the type locality) (Bergquist & Cook 2002). Comparative material examined. Sponge specimens used in the revision of Halisarca dujardini were collected using SCUBA, in White Sea (Kandalaksha Bay, Chupa Inlet (66 �� 17 ' 32 "N ��� 33 �� 39 ' 39 "E), 3���5 m depth, from algae Fucus ramosus and Laminaria saccharina, July 2000���2004; in Barents Sea, Kola Peninsula, Dalnije Zelentsi (69 ��07' 19 "N ��� 36 ��03' 21 "E) 0.3���0.5 m depth, July, August 2003; in Bering Sea, Avacha Bay (52 �� 46 ' 32 "N ��� 158 �� 36 ' 16 "E) 10-11 m depth, October 18 2008; in Japan Sea the Gulf of Peter the Great near of the Marine Biological station ���Vostok��� (Marine Biological Institute of Russian Academy of Sciences) (42 �� 54 'N ��� 132 �� 38 'W) from rocks and boulders at a depth 0.4���4 m; in North Sea, Norway, Bergen (60 �� 23 ' 29 "N ��� 5 �� 13 ' 46 "E), June 2009, 6 m depth; in North Sea, Netherlands, Zeeland, Goese Sas (51 �� 38 ' 52 "N ��� 3 �� 48 '0"E) 18 m depth, July, 2009; NE Atlantic, North Wales (53 �� 14 ' 6 "N ��� 4 �� 7 ' 48 "W) July 1988, 3 m. We also investigated histologically a piece of the neotype and a piece of Halisarca franz-schulzei Merejkovsky, 1879 from Zoological Institute RAN, St-Petersburg, Russia. Description. External morphology. Predominantly incrusting sponge, 0.3���12 mm thick, forming smooth crusts on shallow water hard surfaces, or globular, 0.5���2 cm in diameter. Frequently a fouling organism (on red and brown algae, ascidians, shells of bivalves and brachiopods, tubes of sedentary polychaetes, hydroid stalks) (Figs. 2, 3). Incrusting forms have multiple oscula 0.3���1 mm in diameter, scattered regularly; globular sponges have one osculum or, occasionally, two oscula with raised rims, approximately 1���2 mm in diameter. Pores are dispersed. A significant reduction in the aquiferous system is characteristic for the latest phases of reproduction (embryo and larvae development). During these periods oscula and pores are rarely observed. Colour is yellow-beige to pale brown (Fig. 2); during last phases of reproduction the specimens have ivory or whitish colour due to the presence of embryos and larvae (Fig. 3). Surface is smooth and slimy. Consistency is soft, gelatinous and slightly elastic. Anatomy. Soft tissues. An ectosomal region up to 27 ��m thick, consists of three layers: (1) The upper layer composed of a mucous acellular cuticle 0.1���0.2 ��m thick (Figs. 4, 6), underlying external parts of T-shaped exopinacocytes and a diffuse collagen region 0.9���3 ��m thick beneath it; (2) the middle layer ~ 5���10 ��m thick containing interlaced collagen fibrils organized into firm tracts. This layer can include rare spherulous cells; and (3) the inner layer, up to 3���7 ��m thick, consisting of condensed collagen fibrils and the cell bodies of T-shape exopinacocytes. The choanosome makes up the greatest volume of the sponge body and is composed of choanocyte chambers, canals and mesohyl (Fig. 4). The organization of the aquiferous system is reminiscent of a syconoid system described earlier (L��vi 1956; Vacelet et al. 1989). The long, branching, tubular, meandering choanocyte chambers are arranged radially around a large exhalant canal (Fig. 4). Choanocyte chambers could vary in abundance and size depending on life cycle. During active growth period choanocyte chambers are 120���600 ��m long and 24���90 ��m in diameter. Abundance and length of choanocyte chambers decrease during reproduction (Fig. 5). Cytology. Choanocytes (Figs. 7, 8) are cylindrical or trapeziform, with long and numerous basal pseudopods (Vacelet et al. 1989; Boury-Esnault et al. 1990; Gonobobleva & Maldonado 2009). The cells are 6���9.5 ��m long and 3.5���5 ��m wide, with a smooth flagellum and a collar composed of 30���40 microvilli. Some but not all cells have a periflagellar asymmetrical cytoplasmic sleeve. Choanocytes within a choanocyte chamber are connected with each other at the basal-lateral surfaces with numerous interdigitations. Nuclei are pyriform (2.5 x 4.8 ��m) with apical thinning and often with one to three nucleoli. Cytoplasm contains phagosomes, electron transparent vacuoles, perinuclear Golgi complexes, and mitochondria. Exopinacocytes (Figs. 9���11) are T-shaped. External flat cytoplasmic parts connect with each other by interdigitations. Cell bodies, including the nucleus and the main cytoplasm volume, are situated beneath the ectosome. Cell bodies are connected with flat cytoplasmic parts by thin and long cytoplasmic bridges. Nuclei are nucleolated. Endopinacocytes (Figs. 12, 13) are flat fusiform or polygonal in shape. A nucleolated nucleus is oval, 1.6��� 2 x 3���3.8 ��m in size, and is located in the center of the cell. The cytoplasm includes well-developed Golgi complexes, small electron dense spherical inclusions and abundant electron-transparent vacuoles. Basopinacocytes (Figs. 14, 15) are flattened and polygonal, about 8���14 ��m in length and about 2 ��m in width. The cytoplasm includes a well-developed Golgi complex, small electron dense spherical inclusions and some phagosomes. Mesohylar cells. L��vi (1956) was the first to describe the free cells in the mesohyl of H. dujardini at light microscopy level. He distinguished three cells populations (types): (1) amoeboid or star-shaped cells with spherical central nucleus and clear cytoplasm containing small granules, called ���amoebocytes I and II���, or amoebocytes and collencytes; (2) the cells with the cytoplasm filled with acidophilic granules, called ���amoebocytes III���, or fuchsinophil cells, or granular cells; and (3) cells with large peripheral nucleus and the cytoplasm filled with big spherical inclusions ��� spherulous cells. In subsequent works (Bergquist 1996; Bergquist & Cook 2002) three types of mesohylar cells were also mentioned: (1) lophocytes; (2) spherulous cells, common in the zone between ectosome and choanosome and along canals; and (3) fuchsinophilic cells scattered throughout the choanosome. However, the use of electron microscopy led to recognition of six mesohylar cells types in H. dujardini: (1) amoebocytes, (2) collencytes or lophocytes, (3) spherulous cells, (4) granular cells, (5) microgranular cells, and (6) vacuolar cells (Volkova & Zolotareva 1981; Korotkova & Ermolina 1986; Sukhodolskaya & Krasukevitch, 1984), which are described below. (1) Archaeocytes (���amoebocytes I���) (Figs. 16, 17) are abundant cells in H. dujardini mesohyl. These cells have an irregular amoeboid shape and often produce pseudopodia. A large spherical nucleolated nucleus (2.5���3.5 ��m in diameter) is located in the center of the cell. Cytoplasm is characterized by the absence of any special or monotypical inclusions, although it can contain heterophagosomes and various osmiophilic or electron-transparent inclusions. There are well developed Golgi complex and endoplasmic reticulum. Archaeocytes are distributed throughout the mesohyl. (2) Lophocytes (Figs. 18, 19) have a star-like, clavate, or oval form, often with a tuft of secreted collagen fibrils attached to the lateral and posterior ends. The cytoplasm contains some phagosomes and small osmiophilic inclusions. An oval nucleolated nucleus is located in the anterior part of the cell. (3) Spherulous cells (Fig. 20) are oval or round in appearance (8���12 ��m in diameter) and are characterized by the presence in the cytoplasm of 2���7 large trapeziform, spherical, or oval homogenous osmiophilic inclusions 2���8 ��m in diameter. These inclusions have a microgranular structure. The cytosol is reduced to a thin layer between these inclusions. The cytoplasm sometimes contains large heterogenous inclusions and small electron transparent vacuoles. The Golgi complex is well developed. A nucleus without nucleoli could be in the cell���s center or at the periphery. Spherulous cells can be distributed anywhere in the mesohyl, but are more common in external parts of the choanosome. They often occupy the collagen-reinforced layer in the sponge ectosome. (4) Granular cells (amoebocytes III or fuchsinophilic cells) (Fig. 20) form one of the more numerous cell types in the mesohyl. The shape of these cells is highly variable; usually cells are irregular, ovoid or elongate with a mean diameter about 8 ��m. The cytoplasm is filed with round or oval electron-dense homogenous granules (0.5��� 2 ��m in diameter). The nucleus has a peripheral, or, rarely, central location in the cell. The cells are distributed throughout the choanosome. (5) Microgranular cells (Fig. 20). We propose to distinguish this cell type in H. dujardini from granular cells. Microgranular cells are characterized by irregular, amoeboid or, rarely, oval shape and have large lobopodia. The cytoplasm is filed with abundant small (0.2���0.5 ��m in diameter) electron-dense spherical or oval inclusions. These inclusions can be of oval shape or rod-shaped. The Golgi complex is well developed. The nucleus can be nucleolated or without nucleoli, located in the cell���s center or at the periphery. Microgranular cells do not display any special localization in the choanosome. (6) Vacuolar cells (Fig. 20) are rare in the mesohyl of H. dujardini but do not represent a stage in the ontogenesis of spherulous cell, as thought by L��vi (1956). Cells are irregular to oval in shape, 5 x 7���9 x 12 ��m in size. The cytoplasm contains one to 12 vacuoles of oval or elongated shape 0.5���7.2 ��m in diameter. Vacuoles are electrontransparent or could contain very loose mucus-like inclusions, and in sometimes intact symbiotic bacteria. Vacuolar cells are predominantly distributed in the middle part of the choanosome. Additional transient mesohylar cell types could differentiate at various stages in the life cycle. They can be nutritive cells, macrophages, and special granular cells containing cationic peptides and proteins. Nutritive cells (Fig. 21) are a mixed heterogeneous cell population with predominance of dedifferentiated choanocytes. Choanocytes filled with phagosomes leave choanocyte chambers and enter the mesohyl during oocytes vitellogenesis (Korotkova & Apalkova 1975; Korotkova & Aisenshtadt 1976; Aisenshtadt & Korotkova 1976). Among the nutritive cells there are also amoebocytes I and spherulous cells. Nutritive cells are phagocyted by growing oocytes for yolk granules formation. Macrophages (Fig. 22) are large cells that appear at the end of sexual reproduction when begins the postreproductive restoration phase of the life cycle (Ereskovsky 2000), or during the regeneration when it undergoes destructive processes in the mesohyl (Korotkova & Movchan 1973; Volkova & Zolotareva 1981; Korotkova & Ermolina 1986 b; Sukhodolskaya & Krasukevitch 1984). Cell dimensions can reach 30���35 ��m, the cytoplasm is filled with large heterogeneous phagosomes. A large spherical nucleus is nucleolated. Special eosinophilic granular cells (Fig. 23) contain cationic peptides and proteins (Krylova et al. 2004). These cells are amoeboid or oval in shape (about 8���12 ��m in diameter); the nucleus is oval and voluminous (about 3.2 ��m in diameter) with condensed heterochromatin or a small nucleolus. The cytoplasm contains several specific inclusions: (1) vacuoles that include one to ten round or oval electron-dense granules with peripheral thinly-fibrillar material; (2) vacuoles with electron-dense fine-granular inclusions; (3) electron-dense thinly-fibrillar inclusions located in the cytoplasm. Cells differentiate at the beginning of vitellogenesis of oocytes. During the embryonic development they concentrate in the mesohyl surrounding embryos. These eosinophilic granular cells (or eosinophilic amoebocytes) of maternal sponge penetrate developing embryos and remain there until the beginning of metamorphosis (Korotkova & Ermolina 1982; Ereskovsky & Gonobobleva 2000; Gonobobleva & Ereskovsky 2004 a, b). Symbiotic bacteria. Symbiotic bacteria of H. dujardini are represented by a single morphotype found both in the mesohyl of all investigated adults (Fig. 20) and during all stages of embryonic development of the White Sea specimens (Ereskovsky et al. 2005). Bacteria are almost evenly distributed in the mesohyl and do not form accumulations. Sometimes bacteria are located in vacuoles of archaeocytes. Bacteria (likely gram-positive) have a curved spiral form, characteristic of spirills (Fig. 20). Their length is about 0.45 ��m, thickness 0.18 ��m, the cell wall is 0.05 ��m thick. No flagella or piles are found at the surface of bacterial wall. The cytoplasm is heterogeneous. Its peripheral part has a medium electronic density, while the central part is electron dense and possibly corresponds to the nucleoid. In-between, a thin electron-transparent layer is visible. Reproduction. The sponge is dioecious (however some rare individuals could be hermaphrodites) with short seasonal period of reproduction (Table 2). Spermatogenesis occurs only during the cold part of the year (Ereskovsky 2000). Larvae are sub-spherical to oval dispherulae, 100���200 ��m in diameter, completely ciliated but only sparsely so at the posterior pole (Ereskovsky & Gonobobleva 2000; Gonobobleva & Ereskovsky 2004 a, b). Habitat. Halisarca dujardini is usually found at depths from 1 to 20 m but also from upper littoral (Barents Sea) to 300 m (Skagerrak), mainly on the algae Fucus vesiculosus, F. serratus, Ascophyllum nodosum and Laminaria saccharina, under and on stones and boulders, in empty shells of lamellibranchs, on carapaces of crabs, at the base of gorgonians, and on the ascidian Styela rustica. Distribution. Halisarca dujardini species complex is considered to be cosmopolitan (Bergquist & Cook 2002). In fact, however, its distribution is limited to temperate waters: in the North Atlantic���along the European costs from English Channel to White Sea and in Atlantic coast of USA (Massachusetts) and in the North-West of Mediterranean Sea; in North Pacific���Bering Sea, Avacha Bay and in Russian coast of Japan Sea; in South Pacific���the New Zealand coasts (Fig. 24). See Annex 1 for the detailed distribution. Material examined. Holotype: collected in ���Grotte �� Corail��� Maire Island, 16 m depth, 43 �� 12 ' 38.04 "N ��� 5 �� 19 ' 56.80 "E, Mus��um National d'Histoire Naturelle (Paris, France) MNHN DJV 128. Paratype: collected in ���Grotte �� Corail��� Maire Island, 16 m depth, 43 �� 12 ' 38.04 "N ��� 5 �� 19 ' 56.80 "E, Zoological Institute RAS (Saint-Petersburg, Russia) № 11141. Description. External morphology. Thinly incrusting sponge, 0.17���0.19 mm thick, spreading on the surface of the living bryozoan Smittina cervicornis (Fig. 25, 26). The sponge covers the host���s colony from the base to the tips of the branches with a continuous layer. Most often, the sponge coating is very thin and transparent, and thus hardly visible. The sponge may become relatively thick and then appears as an opaque sheath. The surface is skinlike, lustreless and smooth, even (Fig. 26). Oscula have a cone shape (height: 0.1���0.5 ��m and diameter about 0.5 mm) and are located exclusively along the bryozoan branch edges that are devoid of zooid orifices. Texture is soft, very delicate and easily torn. The colour is pale-yellow. Internal organization. Soft tissue organization. There is a thin ectosomal region, 4���14 ��m deep, consisting of the flat part of exopinacocytes and of an underlying dense collagen layer, about 1.7���2.6 ��m deep (Fig. 27). This layer contains symbiotic bacteria and some secretory cells (Fig. 27). Cell bodies of T-shape exopinacocytes and rare spherulous cells occur beneath the collagen layer. The choanosome makes up most of the volume of the sponge body and is composed of choanocyte chambers and mesohyl (Figs. 27, 28). The individual choanocyte chambers are tubular in shape, sometimes branched, measuring from 76 up to 175 ��m in length and are 9.3���14 ��m wide. There are mobile cells present in the mesohyl. The basal part (Fig. 29), in contact with the bryozoan surface, includes a dense, thin (0.17 ��m) cuticle secreted by the basopinacocytes. Collagen cuticle includes spiral symbiotic bacteria and other bacteria, which are not present in other sponge parts. Cytology. Exopinacocytes (Fig. 30) are T-shaped with a thin, flattened external cytoplasmic part, and an internal cell body. The cell body is irregular or triangular in shape, about 4.9 x 5.3 ��m. The two parts of the cell are connected by a thin cytoplasmic bridge. Nucleus is lightly ovoid (2.2���2.4 ��m in diameter), often without nucleolus. Choanocytes (Fig. 28, 31) are elongate or roughly pyramidal, 2.3���5.3 ��m wide at the base and 1.9���4.2 ��m wide at the nucleus area, the height is 4���5.9 ��m. Choanocyte collar arises at approximately 4 / 5 of the height of the cell and is composed of about 18 microvilli. Nucleus is central or apical, spherical about 1.9 ��m in diameter, occasionally with a nucleolus, 0.5 ��m in diameter. The apical part of choanocytes encompasses many small vacuoles. The central and basal cytoplasm usually contains 2���4 phagosomes, 0.8���1.5 ��m in diameter with heterogeneous inclusions. The choanocytes also contain mitochondria, osmiophilic granules (0.3���0.6 ��m), electron transparent vacuoles (0.1���0.8 ��m) and other inclusions. The choanocytes contact each other only at the base. Long fine pseudopodia frequently arise from the central and basal parts of the choanocytes; the latter anchor choanocytes in the mesohyl. The free apical surface of the choanocytes and the flagella are covered by a thin (1 ��m) glycocalyx layer. Endopinacocytes (Fig. 32), Published as part of Ereskovsky, Alexander V., Lavrov, Dennis V., Boury-Esnault, Nicole & Vacelet, Jean, 2011, Molecular and morphological description of a new species of Halisarca (Demospongiae: Halisarcida) from Mediterranean Sea and a redescription of the type species Halisarca dujardini, pp. 5-31 in Zootaxa 2768 on pages 10-25, DOI: 10.5281/zenodo.206842, {"references":["Levi, C. (1956) Etude des Halisarca de Roscoff. Embryologie et systematique des demosponges. Archives de Zoologie experimentale et generale, 93, 1 - 184.","Bergquist, P. R. (1996) The marine fauna of New Zealand. Porifera, Class Demospongiae. Part 5: Dendroceratida & Halisarcida. Memoirs of the New Zealand Oceanographic Institute, 107, 1 - 53.","Bergquist, P. R. & Cook, S. C. (2002) Order Halisarcida Bergquist, 1996. In: Hooper, J. N. A. & Soest van, R. W. M. (Eds.), Systema Porifera: A guide to the classification of sponges, Kluwer Academic / Plenum Publishers, New York, pp. 1089.","Johnston, G. (1842) A history of British sponges and lithophytes. Lizard, WH, Edinburgh, 264 pp.","Lendenfeld, R. von (1889) A monograph of the Horny Sponges. Trubner and Co, Ludgate Hill, EC, London, 936 pp.","Laubenfels, M. W. de (1948) The order Keratosa of the phylum Porifera. A monographic study. Allan Hancock Foundation Publications Occasional Paper, 3, 1 - 217.","Chen, W. T. (1976) Reproduction and speciation in Halisarca. In: Harrison, F. W. & Cowden, R. R. (Eds.), Aspects of sponge biology, Academic Press, New York, pp. 113 - 140.","Ereskovsky, A. V. (1993) Addition to the fauna of sponges (Porifera) of the White Sea. Vestnik of St-Petersburg University, 2, 3 - 12.","Merejkowsky, C. D. (1878) Les eponges de la mer Blanche. Memoires de l'Academie imperiales des Sciences de St Petersbourg, 26, 1 - 51.","Bowerbank, J. S. (1866) A monograph of the British Spongiadae. Robert Hardwicke, London, 388 pp.","Topsent, E. (1893) Nouvelle serie de diagnoses d'eponges de Roscoff et de Banyuls Archives de Zoologie experimentale et generale, 1, 33 - 43.","Vacelet, J., Boury-Esnault, N., De Vos, L. & Donadey, C. (1989) Comparative study of the choanosome of Porifera: II. The Keratose Sponges. Journal of Morphology, 201, 119 - 129.","Boury-Esnault, N., De Vos, L., Donadey, C. & Vacelet, J. (1990) Ultrastructure of choanosome and sponge classification. In: Rutzler, K. (Ed.), New Perspectives in Sponge Biology, Smithsonian Institution Press, Washington, pp. 237 - 244.","Gonobobleva, E. L. & Maldonado, M. (2009) Choanocyte ultrastructure in Halisarca dujardini (Demospongiae, Halisarcida).","Volkova, M. A. & Zolotareva, G. A. (1981) The development of Halisarca dujardini Johnston from conglomerates of somatic cells. In: Korotkova, G. P., (Ed.), Morphogenesis in sponges, Leningrad University Press, Leningrad, pp. 74 - 92.","Sukhodolskaya, A. N. & Krasukevitch, T. N. (1984) The effect of inozine on the development of Halisarca dujardini from small fragments of the body. Vestnik of Leningrad University, 3, 56 - 62.","Korotkova, G. P. & Apalkova, L. V. (1975) Oogenesis of the Barents Sea sponge Halisarca dujardini Johnston. In: Tokin, B. P., (Ed.), Comparative and experimental morphology of the sea organisms, Kola Filial Academy of Sciences USSR Press, Murmansk, pp. 9 - 26.","Korotkova, G. P. & Movchan N. A. (1973) The peculiarities of defensive-regenerational processes of the sponge Halisarca dujardini. Vestnik Leningradskogo Universiteta, 21, 16 - 25.","Korotkova, G. P. & Ermolina, N. O. (1986 b) Destruction of embryos during the reproductive period in the White Sea sponge Halisarca dujardini Johnston (Demospongiae). Vestnik Leningradskogo Universiteta (Biologia), 4, 104 - 106.","Krylova, D. D., Aleshina, G. M., Kokryakov, V. N. & Ereskovsky, A. V. (2004) Antimicrobal propeties of mesohylar granular cells of Halisarca dujardini Johnston, 1842 Demospongiae, Halisarcida). In: Pansini, M., Pronzato, R., Bavestrello, G., & Manconi, R., (Eds.), Sponge science in the new millennium. Bollettino dei Musei e degli Instituti Biologici dell' Universita di Genova, 68, pp. 399 - 404.","Korotkova, G. P. & Ermolina, N. O. (1982) The larval development of Halisarca dujardini (Demospongiae). Zoological Journal, 61, 1472 - 1480.","Ereskovsky, A. V. & Gonobobleva, E. L. (2000) New data on embryonic development of Halisarca dujardini Johnston, 1842 (Demospongiae, Halisarcida). Zoosystema, 22, 355 - 368.","Gonobobleva, E. L. & Ereskovsky, A. V. (2004 a) Metamorphosis of the larva of Halisarca dujardini (Demospongiae, Halisarcida). Bulletin de l'Institut royal des Sciences naturelles de Belgique, Biologie, 74, 101 - 115.","Gonobobleva, E. L. & Ereskovsky, A. V. (2004 b) Polymorphism in free-swimming larvae of Halisarca dujardini (Demospongiae, Halisarcida). In: Pansini, M., Pronzato, R., Bavestrello, G. & Manconi, R., (Eds.), Sponge science in the new millennium. Bollettino dei Musei e degli Instituti Biologici dell' Universita di Genova, 68, pp. 349 - 356.","Ereskovsky, A. V., Gonobobleva, E. L. & Vishnyakov, A. E. (2005) Morphological evidence for vertical transmission of symbiotic bacteria in the viviparous sponge Halisarca dujardini Johnston (Porifera, Demospongiae, Halisarcida). Marine Biology, 146, 869 - 875.","Duran, S. & Rutzler, K. (2006) Ecological speciation in a Caribbean marine sponge. Molecular Phylogenetics and Evolution, 40, 292 - 297.","Lavrov, D. V. (2010) Rapid proliferation of repetitive palindromic elements in mtDNA of the endemic baikalian sponge Lubomirskia baicalensis. Molecular Phylogeneny and Evolution, 27, 757 - 760.","Lavrov, D. V., Wang, X. & Kelly, M. (2008) Reconstructing ordinal relationships in the Demospongiae using mitochondrial genomic data. Molecular Phylogeneny and Evolution, 49, 111 - 124."]}

Bajalus Lendenfeld, 1885 Diagnosis. Halisarcida in which the choanocyte chambers are tubular, branched, and wide mouthed. Larvae are incubated dispherulae (a larval form found only in Halisarca) with simple undifferentiated histology and cilia of uniform length. Skeleton is composed of fibrillar collagen only, there are no fibrous or mineral elements present; ectosomal and subectosomal collagen is highly organised and structurally diversified (modified from Bergquist & Cook 2002). Type species: Halisarca dujardini Johnston, 1842: 192., Published as part of Ereskovsky, Alexander V., Lavrov, Dennis V., Boury-Esnault, Nicole & Vacelet, Jean, 2011, Molecular and morphological description of a new species of Halisarca (Demospongiae: Halisarcida) from Mediterranean Sea and a redescription of the type species Halisarca dujardini, pp. 5-31 in Zootaxa 2768 on page 10, DOI: 10.5281/zenodo.206842, {"references":["Bergquist, P. R. & Cook, S. C. (2002) Order Halisarcida Bergquist, 1996. In: Hooper, J. N. A. & Soest van, R. W. M. (Eds.), Systema Porifera: A guide to the classification of sponges, Kluwer Academic / Plenum Publishers, New York, pp. 1089.","Johnston, G. (1842) A history of British sponges and lithophytes. Lizard, WH, Edinburgh, 264 pp."]}

A new species of sponge without skeleton, Halisarca korotkovae sp. nov. is described from the Sea of Okhotsk. It differs from the other species of Halisarca by its different ecological conditions, as well as by its morphology and histology. The new species is characterized by its fulvous colour and by its big nucleolated, eosinophilic microgranular cells (18.7×9.5 to 10.8×7.1 μm) concentrated mainly in the ectosomal part of sponge in aggregates up to 40 μm in diameter.

Halisarca korotkovae sp. nov. (Figs. 2���4) Material examined. Holotype ZIN RAS 10700 - (49 �� 57 ���, 7���50 ��00���, 6 N, 145 �� 51 ���, 3���49 ���, 1 E), SW of Sea of Okhotsk, 600 m, 0 8 Oct. 1984, collector A.V. Ereskovsky. Paratypes: ZIN RAS 10701 - (50 ��02���, 5 ���05���, 3 N, 145 �� 32 ���, 2���30 ���, 6 E), SW of Sea of Okhotsk, 490���500 m, 0 8 Oct. 1984; ZIN RAS 10702 - (50 �� 59 ���, 2���51 ��02���, 2 N, 145 �� 21 ���, 2���19 ���, 2 E), SW of Sea of Okhotsk, 620���645 m, 10 Oct. 1984; ZIN RAS 10703 - (55 �� 30 ���, 7���30 ���, 7 N, 150 ��00���, 5 ���08���, 4 E), central part of Sea of Okhotsk, 300 m, 20 Oct. 1984; ZIN RAS 10704 - (55 �� 13 ', 3���10 ', 8 N, 148 �� 49 ���, 3���55 ���, 4 E), central part of Sea of Okhotsk, 500 m, 20 Oct. 1984. Collector is A.V. Ereskovsky. Description. The sponge is encrusting, 1���3 mm thick, spreading on a skeleton of Aphrocallistes sp. (Hexactinellida) and forming patches from 1 cm up to 5 cm in diameter. Surface is skin-like, smooth, shiny, even or bearing a slight undulation (Fig. 2). Texture is softly collagenous, easily torn. No oscules or pores visible in preserved specimens. Colour in life is dull brownish-yellow, pigmentation is uniform throughout the sponge body. Soft tissue organisation. A thin ectosomal region 17 to 55 ��m deep is bounded by a cuticle from 2.9 to 5 ��m deep (Fig. 3 A). The cuticle is mucus-like and acellular���the product of ectosome cell secretion overlapping all of the sponge surface (Figs. 3 A, 4 A). Beneath this cuticle is a dense cellular layer in which the cell bodies of T-shaped exopinacocytes occur, as well as conglomerates of big microgranular cells, rare spherulous cells, and vacuolar cells. Below this layer, cell density is greatly reduced in the mesohyl between the abundant inhalant canals and subectosomal cavities (Fig. 3 A). The choanosome makes up the greatest volume of the sponge body and is composed of choanocyte chambers and mesohyl (Fig. 3 B). The choanocyte chambers are meandering tubular, long, branching, and tight with diameter of 1.5 to 10 ��m and length up to 120 ��m (Figs. 3 B, 4 B). Cytology. Exopinacocytes (Fig. 4 A) are T-shaped, as typical for order, with thin external cytoplasmic part and internal cell body part. The cell body, about 3.4 ��m in diameter, is oval or irregular in form. Both parts are connected by a thin cytoplasmic bridge. Endopinacocytes (Fig. 4 B) are flat, nonflagellate cells with nucleolate nucleus. The length is about 14 ��m and the thickness in the nucleus region is about 1.8 ��m. Choanocytes are small, elongated, monoflagellate cells about 3.3 �� 2.1 ��m with anucleolate nucleus. Big microgranular cells (Figs. 3 A, 4 A) are distinctive cells of the new species. These cells are concentrated mainly in the ectosome of the sponge. They are large, oval or egg-shaped (18.7 �� 9.5 to 10.8 �� 7.1 ��m) with nucleolate nucleus (nucleolus diameter 1 ��m). The cytoplasm is eosinophilic and filled with numerous small (0.5 ��m in diameter) homogenous granules. These cells are often concentrated in aggregates up to 40 ��m in diameter (Fig. 4 A). Vacuolar cells (Fig. 4 A, C) are oval or irregular (approximately 7.6 ��m in diameter) eosinophyllic cells with anucleolate nucleus. The cytoplasm contains big semi-transparent vacuoles (0.2���0.7 ��m in diameter) often with microgranular inclusions. These cells are dispersed in the ectosome (Fig. 4 A) and choanosome (Fig. 4 C). Spherulous cells (Fig. 4 A, B, D) are oval (6.2 - 7.9 ��m in diameter) with anucleolate nucleus. The cytoplasm is filled with spherical granules (diameter from 0.8 to 2.9 ��m) homogenous in content. These cells are dispersed in the ectosome (Fig. 4 A) choanosome (Fig. 4 B, D). Amoebocytes (Fig. 4 A, D) are ameboid cells (from 3.3 to 3.8 ��m in diameter) with big nucleolate nucleus (2.1���2.4 ��m in diameter), dispersed in all parts of the sponge mesohyl. Reproduction. In all investigated specimens there were many oocytes (Fig. 4 D) in an early stage of oogenesis before vitellogenesis. Oocytes have oval (from 9.2 to 14.5 ��m in diameter) or elongated form (from 14.5 �� 8.3 ��m to 22.9 �� 7.9 ��m) and are dispersed in the mesohyl of the choanosome. The nucleus (about 5.2 ��m in diameter) contains a nucleolus (2.9 ��m in diameter). Habitat and distribution. Specimens of Halisarca korotkovae sp. nov. occur as thin sheets on the skeleton of a hexactinellid sponge Aphrocallistes sp. (Hexactinosida, Aphrocallistidae) in the SW and central parts of Sea of Okhotsk at a depth from 300 to 645 m (Fig. 1). The bottom consists of silt, pebbles and fragments of hexactinellid Aphrocallistes sp. skeleton. Etymology. The species name refers to the famous Russian spongologist, Prof. Galina P. Korotkova (Saint-Petersburg State University)., Published as part of Ereskovsky, Alexander V., 2007, A new species of Halisarca (Demospongiae: Halisarcida) from the Sea of Okhotsk, North Pacific, pp. 57-66 in Zootaxa 1432 on pages 62-65, DOI: 10.5281/zenodo.175835

Bajalus Lendenfeld, 1885 Diagnosis. As for the Order Type species: Halisarca dujardini Johnston, 1842: 192., Published as part of Ereskovsky, Alexander V., 2007, A new species of Halisarca (Demospongiae: Halisarcida) from the Sea of Okhotsk, North Pacific, pp. 57-66 in Zootaxa 1432 on page 61, DOI: 10.5281/zenodo.175835

Family Halisarcidae Schmidt, 1862 Diagnosis. As for the Order, Published as part of Ereskovsky, Alexander V., 2007, A new species of Halisarca (Demospongiae: Halisarcida) from the Sea of Okhotsk, North Pacific, pp. 57-66 in Zootaxa 1432 on page 61, DOI: 10.5281/zenodo.175835

Genus Oscarella Vosmaer, 1884 Type species. Halisarca lobularis Schmidt, 1862 (by monotypy). [Oscaria] Vosmaer, 1881: 163 (preocc. by Oscaria Gray, 1873 ��� Reptilia); Oscarella Vosmaer, 1884: pl. 8 (explanation); 1887: 326 (nom. nov. for Oscaria Vosmaer). Octavella Tuzet and Paris, 1964: 88. Diagnosis (Muricy & Diaz 2002). Plakinidae without skeleton, with thinly encrusting to lobate shape. Thin ectosome (, Published as part of Ereskovsky, Alexander V., 2006, A new species of Oscarella (Demospongiae: Plakinidae) from the Western Sea of Japan, pp. 37-51 in Zootaxa 1376 on page 38, DOI: 10.5281/zenodo.174988, {"references":["Muricy, G. & Diaz, M. C. (2002) Order Homosclerophorida Dendy, 1905, family Plakinidae Schulze, 1880. In: Hooper, J. N. A. & Soest, R. W. M. van (Eds), Systema Porifera: A guide to the classification of sponges, Kluwer Academic / Plenum Publishers, New York, pp. 71 - 81."]}

Oscarella malakhovi sp. nov. (Figs. 2���8) Material examined. Holotype ZIN RAS 10697 ��� Russia, Japan Sea, Gulf of the Peter the Great, Vostok Bay, Pashennikov Cape, (42 �� 54 ��� 50 ������ N ��� 132 �� 38 ��� 44 ������ W), 0.2 m, the boulders, 11.08. 2006, collector A.V. Ereskovsky. Paratypes: ZIN RAS 10698 ��� Russia, Japan Sea, Gulf of the Peter the Great, Vostok Bay, Pashennikov Cape, (42 �� 54 ��� 50 ������ N ��� 132 �� 38 ��� 44 ������ W), 0.2 m, 11.08. 2006, collector D.B. Tokina; ZIN RAS 10699 ��� the same locality, 4 m, the stones, silt, 0 9.08. 2006, collector A.V. Ereskovsky. Diagnosis. Intertidal and upper supralittoral Oscarella, pinky-beige to yellow in color, with lumpy, microlobate surface, soft, slimy consistency, two particular kinds of cells with inclusions (vacuolar and granular cells), and with two endobiont bacteria species. Description. Thinly encrusting, irregular, lobate sponge, generally pinky-beige, or yellow color, from 0.8���1.5 up to 3���8 cm in diameter, with a soft, slimy consistency. Lobes are small, round, and irregular (Fig. 2). The surface is perforated by abundant inhalant ostia 9���12 ��m in diameter (Fig. 3). Most specimens are 1���2 mm thick, and lumpy or undulating with a few oscular tubes about 1���2 mm in height. The sponge is loosely attached to the substratum. Under low magnification (40 ��) the colorless spherical choanocyte chambers can be seen in the living material, and orange spherical embryos. Soft tissue organisation. A spicule and fibre skeleton is absent. The ectosome is 8���15 ��m thick. Inhalant canals (6 ��� 3 ��m in diameter) run perpendicular to the surface (Fig. 3). Choanocyte chambers are ovoid to spherical eurypilous, 12���33 ��m in diameter (Fig. 4 A, C). Exhalant canals run towards a well-developed system of basal exhalant cavities about 38 ��m in diameter, lead to the oscula. Ostia are 9���12 ��m in diameter (Fig. 4 B, D). Cytology. Choanocytes ovoid to pyramidal, irregular, 2.9 ��m in the base and 4.1 ��m high (Fig. 5 A, B). Nucleus basal or, rarely apical, 2 ��m in diameter. Cytoplasm with up to eight phagosomes from 0.6 to 2.3 ��m in diameter. The collar measures 1.9 ��m in width with about 27 microvilli. The choanocytes contact each other at their middle sections. Their basal parts show no or very rare pseudopodia. Apopylar cells (Fig. 5 B, C) are roughly triangular in section, 8.4 ��m wide by 3.6 ��m in high. Nucleus is spherical, up to 2.3 ��m in diameter. Cytoplasm contains mitochondria, digestive vacuoles, and small osmiophilic inclusions. Endopinacocytes (Fig. 5 D, E) are flat to irregular, flagellated 6.7 ��m wide by 2.2 ��m high. They are anchored in the mesohyl by long thin basal pseudopodia. Their free surface is studded with cytoplasmic projections. Nucleus is ovoid (2.3 ��m in diameter), often with the nucleolus. The cytoplasm contains inclusions and phagosomes from 0.6 to 2.3 ��m in diameter. Exopinacocytes (Figs. 4 D; 5 F) are similar to the exopinacocytes (5.4 ��m wide by 2.3 ��m high), except in their flat free surface. A thin irregular layer of glycocalyx covers the surface of exopinacocytes, endopinacocytes, choanocytes and apopylar cells. Choanoderm and pinacoderm are lined by a basement membrane-like structure, which is a continuous, from 0.4 to 0,2 ��m thick layer of condensed collagen fibrils in the mesohyl closely adjacent to the base of the cells (Fig. 5 B). Archaeocytes ( Fig. 6 A, B ) very rare, ovoid to irregular, 4.6 ��m. The cytoplasm has small phagosomes and rare electron transparent vacuoles from 0.6 to 1.1 ��m in diameter. Nucleus ovoid or irregular, 2.6 ��m, nucleolated. Within the mesohyl two types of cells with inclusions are observed. Granular cells (Fig. 6 C) are very rare, ovoid, about 4.5 ��m. Cytoplasm filled with oval electron dense granules 1.1 ��m. Nucleus, irregular 1.8 ��m in diameter, without a nucleolus. Vacuolar cells (Figs. 5 C, F; 6 D) abundant, often near the choanocytes chambers or exopinacoderm. These cells are ovoid to irregular 6.1 ��m. Nucleus 1.7 ��m in diameter, ovoid or compressed by the vacuoles. Cytoplasm with, 3���6 larger vacuoles, 2.9 ��m in diameter, with clear and filamentous contents, 3���7 small inclusions (1.4 ��m in diameter) with electron-dense homogeneous contents from spherical to triangulate, and pahgosomes 1 ��m in diameter. This cell type to be involved in the secretion of ground substances of the intercellular matrix, because it is often seen liberating the contents of its larger, clear vacuoles in the mesohyl (Fig. 6 D). Symbiotic bacteria. Endobiont bacteria of two kinds occur in the mesohyl: B 1 and B 2 both are extracellular (Figs. 5 D; 6 A, C; 7 A, B). B 1 is more numerous, oval peanutshaped, has a length of 1.1���1.7 ��m and diameter: 0.5���0.9 ��m. The cell wall is the Gramnegative. Under the cell wall there is a vast transparent space with filaments. The thickness of the space is very variable. A filamentous network of the nucleoid is irregular: thick elements are in center and thin filaments are closer to periphery of the cell. Near the cytoplasmic membrane a small layer of granular cytoplasm occurs. B 2 type is elongated with the length 0.4���1.1 ��m and diameter 0.19���0.3 ��m. The cell wall is Gram-negative and consists of two membranes, under which a thin electron transparent space is found. The thick nucleoid filaments form a more ordered voluminous structure with thin periphery of the dark cytoplasm. Development. During the end of July ��� the end of August sponges are full of oocytes and embryos at different developmental stages: from two blastomeres to larva (Fig. 3 A, B). The larva is a typical homoscleromorph cinctoblastula with the lateral-posterior zone of the cells with intranucleolar paracristalline inclusion and basement membrane. In the larval cavity there are the symbiotic bacteria of two morphotypes. The posterior pole of larvae is colored orange. The O. malakhovi sp. nov. also display asexual reproduction by budding. Numerous small, spherical and transparent buds are visible on the sponge surface (Fig. 8 A, B). The diameter of the buds is from 90 to 140 ��m. Habitat and distribution. Specimens of Oscarella malakhovi sp. nov. occur as thin sheets on the sides of bivalve Crenomytilus grayanus (Dunker, 1853), or on the lower side of stones in the Gulf of the Peter the Great, Vostok Bay (42 �� 54 ��� 50 ������ N ��� 132 �� 38 ��� 44 ������ W) at a depth to 0.4���4 m (Fig. 1). Discussion. The genus Oscarella is cosmopolitan with 8 valid species known from different oceans around the world (Table 1), but only four species are known from the Pacific: two from the Indo-Pacific: O. nigraviolacea and O. stillans (Bergquist & Kelly 2004), one species form the Eastern coast of the former URSS ��� O. lobularis (Koltun 1966). However, this record was considered unrecognizable by Muricy et al. (1996). And one from the Eastern Pacific (California) ��� O. carmela (Muricy & Pearse 2004). The identification of Oscarella at the species level is difficult because species of this genus have no skeleton, and histological characters are homogeneous. The differences among species are mostly in external traits: color, consistency, and aspect of the surface (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy & Diaz 2002; Bergquist & Kelly 2004; Muricy & Pearse 2004). But many of them are greatly subjective to describe. Oscarella malakhovi sp. nov. is unique in color: pinky-beige to yellow color had not seen in other Oscarella species. The surface aspects (smooth, microlobate) are helpful, but one cannot separate all species on that basis alone. The new species is thinly encrusting, irregular, sponges, with soft, slimy consistency, lobes are round and irregular. ZOOTAXA 1376 morphological, anatomical, cytological and ecological characters of Oscarella species. O. lobularis O. tuberculata O. viridis O. microlobata O. imperialis O. stillans O. nigraviolacea O. carmela O. malakhovi Oscarella nigraviolacea Bergquist and Kelly, 2004 differs from the new species by its dark violet, almost black color, and the oscules situated on top of papillae. O. stillans Bergquist and Kelly, 2004 forms a series of fused tubes up to 3.5 cm long, some with solid branches, and it is dark honey yellow in color. It also has a characteristically high collagen deposition in the mesohyl, giving it a collagenous consistency. O. carmela Muricy and Pearse, 2004 differs from O. malakhovi sp. nov. by variability of color and surface characters: from light brown to tan or dull orange color, and from a smooth to microlobate surface. Cytological characters, such as the types of cells with inclusions present, are very important for Oscarella species identification. Cells with inclusions are special sponge cells with different cytoplasmic inclusions, most of which have unknown functions (e.g., Simpson 1984; Muricy et al. 1996, 1999). They are diverse and abundant in species of Oscarella, and each species has a particular set of cells with inclusions that are useful characters for species identification (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy & Pearse 2004). Nowadays at TEM were studied only five Mediterranean and one East-Pacific Oscarella species (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy & Pearse 2004). Oscarella from the Indo-Pacific had not characterized cytologically. The new species is similar to O. carmela, but differs from all other Mediterranean Oscarella species in its cell contents, which are simple, with only two kinds of cells with inclusions: granular cells and vacuolar cells with two different inclusions, osmiophilic and filamentous (Fig. 6 C, D). In contrast, O. carmela the new species has the granular cells, which absent in O. carmela. The archaeocytes of O. malakhovi sp. nov. differ from O. carmela by absence of abundant long pseudopodia. It is interesting, that the basement membrane-like structure of the new species is apparently thicker (0.4 to 0.3 ��m) than in other species of Oscarella ��� 0.005���0.02 ��m (Muricy et al. 1996; Myricy & Pearce 2004). Other useful characters are symbiotic bacteria morphology. Different sponge species from one genus can possess various bacterial morphotypes (Boury-Esnault et al. 1992; Muricy et al. 1996; 1999; Hentschel et al. 2001; Muricy & Pearse 2004). Symbiotic bacteria have been found in the mesohyl of all species of Homoscleromorpha studied so far and the composition of the symbiotic bacterial populations has been shown to be species specific (Boury-Esnault et al. 1992, 1995, Muricy et al. 1996, 1999). As in O. carmela, O. malakhovi sp. nov. has two type of endosymbiotic extracellular bacteria. The differences between the symbiotic bacteria type B 1 in O. malakhovi sp. nov. and O. carmela are: 1 ��� smooth cell without a wrinkles on its wall; 2 ��� the cytoplasm is clear and not dark; 3 ��� has biggest dimension then in O. carmela. The type B 2 in O. malakhovi sp. nov. is smaller then in O. carmela. The sexual and asexual developmental characteristics of the new species are typical for the other Oscarella species described early (Ereskovsky & Boury-Esnault 2002; Boury-Esnault et al. 2003; Ereskovsky & Tokina 2006). The complete absence of a skeleton is shared the genus Oscarella with Hexadella Topsent, 1896 (Verongida, Ianthellidae), Chondrosia Nardo, 1847, Thymosiopsis, Vacelet & Perez, 1998 (Chondrosida, Chondrillidae), Myceliospongia Vacelet & Perez, 1998 (Demospongiae incertae sedis), Halisarca Johnston, 1842 Halisarcida, Halisarciidae), and Pseudocorticium Boury-Esnault et al., 1995 (Homosclerophorida, Plakinidae). These genera can also be distinguished through examination of histological sections to observe the shape and size of the canals, choanocyte chambers, larvae and cytological features. Within the genus Oscarella cytological (ultrastructural) characters, including cellular composition, cell morphology, particularly the cells with inclusions, are more successful for the species discrimination (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy 1999). The detail cytological analysis of Oscarella species, collected in shallow waters the northwestern Sea of Japan, Russia, allow describing it as a new species., Published as part of Ereskovsky, Alexander V., 2006, A new species of Oscarella (Demospongiae: Plakinidae) from the Western Sea of Japan, pp. 37-51 in Zootaxa 1376 on pages 40-49, DOI: 10.5281/zenodo.174988, {"references":["Bergquist, P. R. & Kelly, M. (2004) Taxonomy of some Halisarcida and Homosclerophorida (Porifera: Demospongiae) from the Indo-Pacific. New Zealand Journal of Marine and Freshwater Research, 38 (1), 51 - 66.","Koltun, V. M. (1966) Four-rayed sponges of the northern and far eastern seas of the USSR (order Tetraxonida). \" Nauka \" Moscow-Leningrad, 112 pp. (In Russian).","Muricy, G., Boury-Esnault, N. Bezac, C. & Vacelet, J. (1996) Cytological evidence for cryptic speciation in Mediterranean Oscarella species (Porifera, Homoscleromorpha). Canadian Journal of Zoology, 74, 881 - 896.","Muricy, G. & Pearse, J. S. (2004) A New Species of Oscarella (Demospongiae: Plakinidae) from California. Proceedings of the California Academy of Sciences, 55 (33), 598 - 612.","Boury-Esnault, N., Sole-Cava, A. M. & Thorre, J. P. (1992) Genetic and cytological divergence between color morphs of the Mediterranean sponge Oscarella lobularis Schmidt (Porifera, Demospongiae, Oscarellidae). Journal of Natural History, 26, 271 - 84.","Muricy, G. & Diaz, M. C. (2002) Order Homosclerophorida Dendy, 1905, family Plakinidae Schulze, 1880. In: Hooper, J. N. A. & Soest, R. W. M. van (Eds), Systema Porifera: A guide to the classification of sponges, Kluwer Academic / Plenum Publishers, New York, pp. 71 - 81.","Simpson, T. L. (1984) The Cell Biology of Sponges. Springer-Verlag, New York. xix + 662 pp.","Hentschel, U., Schmid, M., Wagner, M., Fieseler, L., Gernert, C. & Hacker, J. (2001) Isolation and phylogenetic analysis of bacteria with antimicrobial activities from the Mediterranean sponges Aplysina aerophoba and Aplysina cavernicola. FEMS. Microbiological Ecology, 35 (3), 305 - 312.","Boury-Esnault, N., Muricy, G., Gallissian, M-F. & Vacelet, J. (1995) Sponges without skeleton: a new Mediterranean genus of Homoscleromorpha (Porifera, Demospongiae). Ophelia, 43 (1), 25 - 43.","Ereskovsky, A. V. & Boury-Esnault, N. (2002) Cleavage pattern in Oscarella species (Porifera, Demospongiae, Homoscleromorpha): transmission of maternal cells and symbiotic bacteria.","Boury-Esnault, N., Ereskovsky, A. V., Bezac, C. & Tokina D. (2003) Larval development in Homoscleromorpha (Porifera, Demospongiae) first evidence of basal membrane in sponge larvae. Invertebrate Biology, 122, 187 - 202.","Ereskovsky, A. V. & Tokina, D. B. (2006) Asexual reproduction in Oscarella (Porifera; Homoscleromorpha. Marine Biology. DOI 10.1007 / s 00227 - 006 - 0439 - 5."]}

Ereskovsky, Alexander V., Bouryesnault, Nicole (2002): Cleavage pattern in Oscarella species (Porifera, Demospongiae, Homoscleromorpha): transmission of maternal cells and symbiotic bacteria. Journal of Natural History 36 (15): 1761-1775, DOI: 10.1080/00222930110069050, URL: http://www.tandfonline.com/doi/abs/10.1080/00222930110069050

Ereskovsky, Alexander V., Gonobobleva, Elisaveta L. (2000): New data on embryonic development of Halisarca dujardini Johnston, 1842 (Demospongiae, Halisarcida). Zoosystema 22 (2): 355-368, DOI: http://doi.org/10.5281/zenodo.5402176