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Highly abundant and widespread populations of the introduced eastern Pacific ophiuroid brittle star Ophiothela mirabilis occur in southeast Florida, extending the range of this new non-native species from southern Brazil northward to the Caribbean Sea and Florida, now spanning about 6000 km of latitude along western Atlantic tropical/subtropical shores. This brittle star species, representing two lineages, is an epizoite on shallow-occurring (3–15 m depth) plexaurid octocorals (e.g., Eunicea spp., Muricea elongata, and Plexaurella dichotoma). Overall body color (disk and arms) is commonly beige or orange; a few individuals display combinations of both colors: orange disk/beige arms or beige disk/orange arms. Population densities in situ commonly ranged between 5 and 12 individuals of O. mirabilis per 10-cm-long octocoral branch with up to six arms generally curled around their octocoral host’s branches. In a 33-day experiment, M. elongata colony surface areas with reduced (contracted) polyps and reduced polyp extension lengths were not statistically different between octocorals with brittle stars versus octocorals without brittle stars. At the end of 33 days, brittle star densities demonstrated an overall decline. In a 66-day experiment, increasing brittle star densities resulted in reduced extended polyp areas in M. elongata, but no changes in Eunicea flexuosa. Polyp extension lengths decreased in both octocoral hosts with increasing densities of O. mirabilis. Overall, experimental brittle star densities did not change, with several octocoral hosts revealing increases in O. mirabilis by means of fissiparity. The presence and increasing densities of O. mirabilis causing a reduction in octocoral polyp extension were greatest in M. elongata but did not result in visible adverse effects to host condition. Black spotting on octocoral stems, a sign of tissue deterioration, was not observed during or after the two experiments. Nearly all experimental octocorals demonstrated tissue growth in the 66-day experiment, expanding over relatively large areas of the supporting pedestals.

The brittle star Stegophiura nodosa is one of the most abundant ophiuroid species living in Arctic seas and serves as a food resource for demersal fish. The study of autecological and biological patterns of S. nodosa is important for understanding the species reaction to environmental change. The growth features and growth rate of this brittle star from the Pechora Sea were estimated using the Gompertz equation as the basic mathematical model and compared with Bertalanffy equation parameters. Individual age was evaluated by counting the ring-shaped growth marks in the calcite structure of the animal's vertebral ossicle, where each visible ring was considered to be an annual growth mark. The calculations indicated: the theoretical limiting radius of the brittle star's ossicle (R∞) averages 318 ± 18 μm, and the exponential deceleration of the specific growth rate (g) is found to be 0.46 ± 0.02. The initial hidden growth marks were found to vary from 1–3, and the maximum lifespan of S. nodosa in the Pechora Sea (SE of the Barents Sea) is evaluated to be 9–10 years.

Two fossil Echinoderms, a starfish (asteroid) and a brittle star (ophiuroid), are described in this paper. They were found in sandstones of Early Cretaceous age in the Te Urewera National Park, Eas...

This study presents the first record of two eulimid species, Stilapex zebra and Pyramidelloides sp., found on the arms of the brittle star Ophiothrix (Acanthophiothrix) purpurea on Spratly Islands (Truong Sa). Previously eulimids were found on ophiuroids only in central Vietnam (Nhatrang Bay), while the current study is the first symbiotic association between eulimids and ophiuroids from another part of the South China Sea (Spratly Islands). For the first time Ophiothrix (Acanthophiothrix) purpurea was recorded as a host species for both Stilapex zebra and Pyramidelloides sp. We can suppose that Ophiothrix (Acanthophiothrix) purpurea, is a generalist symbiont with a high range of hosts (mainly soft corals). If so, this case can be seen as an interesting example of hyper-symbiosis among mobile macroinvertebrates: the brittle star is the symbiont of a soft coral, and the eulimids are the symbionts of the brittle stars.

Since 2012, whenOphiothelawas first described in the Atlantic, there has been no consensus regarding its identification. It has been described asO.mirabilis,O. cf.mirabilis,O.danae, or onlyOphiothelasp. In order to fill these gaps, our aim was to test if specimens from Brazil areOphiothela mirabilisand/orOphiothela danae. Syntypes from the Museum of Comparative Zoology and United States National Museum, Smithsonian Institution, were used. We examined species boundaries of the small six-rayed brittle starOphiothelausing independent character sets utilizing morphology (external morphology and morphometry) and molecular data (16S and COI). Concordance was found between the analyses indicating thatOphiothelasp. from Brazil (BR),Ophiothela mirabilisandOphiothela danaeare closely related. We suggest thatO.danaeshould be considered as a junior synonym ofO.mirabilis. A detailed description ofO.mirabilisBR is presented using external morphology and microstructural ossicles (arm plates, vertebra, dental and oral plates). This description includes new diagnostic features, particularly regarding its microstructures: (i) transspondylous articulation (first record in Ophiotrichidae); (ii) eight smooth knobs on the dorsal surface of the vertebrae (to date only inOphiothela); (iii) vertebrae with distal keel divided into two separate end processes matching the two large dorsal grooves proximally (first time in the literature); and (iv) an opening on both sides of the oral plate (as seen in other fissiparous speciesOphiactis savignyiandOphiocomella ophiactoides).

Autotomy, the self-induced loss of a body structure, occurs in every living class of echinoderms and is related to the remarkable regeneration capabilities of the group. It is particularly prevalent in brittle stars (Class Ophiuroidea). Autotomy is facilitated by mutable collagenous tissue, which undergoes nervous system-mediated changes in tensile stiffness, tensile strength, and viscosity. The previous investigations of autotomy have been based on observations of the external surface, surgical manipulation of internal structures, or data on the morphology of structures post-autotomy. We used fast phase-contrast X-ray synchrotron imaging to visualize full autotomy events in vivo in the arms of specimens of the brittle star Ophioderma brevispina. This method requires no chemical or surgical manipulation and enabled us to identify several key stages in the autotomy process. We used this methodology to observe critical changes within the internal structure of the arm as it transitions from a functional mechanical apparatus to a dysfunctional disarticulated state. This method is the first in which the full intersegmental plane of the arm can be observed during autotomy. It can be applied to visualize autotomy and motion in vivo in other brittle star taxa, as well as in other groups such as asteroids and arthropods.

A new species of brittle star, Ophiodelos okayoshitakai, is described from two specimens collected in Sagami Bay, central-eastern Japan. Photographic examination of the holotype specimen of the sole other congener, Ophiodelos insignis Koehler, 1930, indicates that Ophiodelos okayoshitakai sp. nov. is distinguished from O. insignis by i) the disc stumps covering on the dorsal side of the disc, ii) the dorsal and ventral arm plates being separated from each other on the proximal arm regions, iii) the dorsal arm plate being smooth, iv) the arm spines at proximal portion of the arm being six in number and smooth in shape, and v) the number and shape of the tentacle scales at proximal portion of the arm being up to two and spine-shaped adradially and oval abradially. Detailed morphological observations of this new species suggest the inclusion of Ophiodelos, whose familial affiliation remains unclear, in the suborder Ophiacanthina. More than 10 juveniles of various sizes were found in the disc of Ophiodelos okayoshitakai sp. nov., indicating a brooding reproduction. This is the first report of the genus Ophiodelos from Japanese waters. We also provided a nucleotide sequence for part of the cytochrome c oxidase subunit I (COI) gene in O. okayoshitakai sp. nov. for future studies of DNA barcoding and phylogeny.

Cold-water coral reefs and sponge grounds are deep-sea biological hotspots, equivalent to shallow-water tropical coral reefs. In tropical ecosystems, biodiversity and productivity are maintained through efficient recycling pathways, such as the sponge loop. In this pathway, encrusting sponges recycle dissolved organic matter (DOM) into particulate detritus. Subsequently, the sponge-produced detritus serves as a food source for other organisms on the reef. Alternatively, the DOM stored in massive sponges was recently hypothesized to be transferred to higher trophic levels through predation of these sponges, instead of detritus production. However, for deep-sea sponges, the existence of all prerequisite, consecutive steps of the sponge loop have not yet been established. Here, we tested whether cold-water deep-sea sponges, similar to their tropical shallow-water counterparts, take up DOM and transfer assimilated DOM to associated fauna via either detritus production or predation. We traced the fate of 13carbon (C)- and 15nitrogen (N)-enriched DOM and particulate organic matter (POM) in time using a pulse-chase approach. During the 24-h pulse, the uptake of 13C/15N-enriched DOM and POM by two deep-sea sponge species, the massive species Geodia barretti and the encrusting species Hymedesmia sp., was assessed. During the subsequent 9-day chase in label-free seawater, we investigated the transfer of the consumed food by sponges into brittle stars via two possible scenarios: (1) the production and subsequent consumption of detrital waste or (2) direct feeding on sponge tissue. We found that particulate detritus released by both sponge species contained C from the previously consumed tracer DOM and POM, and, after 9-day exposure to the labeled sponges and detritus, enrichment of 13C and 15N was also detected in the tissue of the brittle stars. These results therefore provide the first evidence of all consecutive steps of a sponge loop pathway via deep-sea sponges. We cannot distinguish at present whether the deep-sea sponge loop is acting through a detrital or predatory pathway, but conclude that both scenarios are feasible. We conclude that sponges could play an important role in the recycling of DOM in the many deep-sea ecosystems where they are abundant, although in situ measurements are needed to confirm this hypothesis.

This study analyzes the fauna composition of the community of brittle and sea stars associated with sponge aggregations located in Avilés Canyons System and El Cachucho, Marine Protected Area (MPA). Diverse sampling methods were used depending on bottom morphology, such as rock dredges and specific samplers for sedimentary bottoms, mainly beam trawl models. These banks are made up of sponge and coral species that build a very appropriate substrate for the proliferation of benthic species, which together create Vulnerable Marine Ecosystems that are highly relevant for management and conservation. Among these benthic species, echinoderms are of great interest due to their value as indicators of good habitat. In total, 1261 specimens were collected (934 brittle stars and 327 starfishes), belonging to 42 species (28 ophiuroids and 14 asteroids) from INDEMARES AVILÉS, ECOMARG, and SponGES project surveys. Specimens were distributed among four sponge aggregations (F: fields) that were considered according to the sponge records obtained in the same stations (36). These fields were defined and named based on the five most common sponge species:Aphrocallistes beatrixandRegadrella phoenix(F1: Avilés Canyon);Pheronema carpenteri(F2: Intraslope basin of Le Danois Bank);Asconema setubalense(F3: Le Danois Bank); andNeoschrammeniellaaff.bowerbankii(F4: Corbiro Canyon). Faunistic results show thatOphiactis abyssicola(55.55% occurrence),Brisinga endecacnemos, Ophiolycus purpureus, andPeltaster placenta(33.33%) were the most frequently found species in F1;Psilaster andromeda(80%),Pseudarchaster parelii(60%), andNymphaster arenatus(46.67%) in F2;Ophiura carnea(71.43%) andOphiacantha smitti(42.86%) in F3; andOphiacantha densa, andHenricia caudani(100%) in F4. The asteroid and ophiuroid species collected seem to be composed of four different communities that fit to areas with particular morphological and biological features, related to the presence of species specialized in the use of the resources they can find there. In general, the abiotic factor controlling this structure is depth. This assemblage structure, which favors the dissimilarity between the canyons and the bank, is not so clear, since the deepest stations are located on the intraslope basin of El Cachucho, Marine Protected Area (MPA), therefore, using ita prioricould lead to misunderstandings. Once the structure of the echinoderm community was known, we compared the expected and obtained results to analyze evidence which should prove the existence of any association between echinoderms and sponges, which enabled us to refute the incongruous hypothesis.

Five specimens of brittle star were collected from a deep-sea seamount in the Northwest Pacific, and identified into three species. One which is new to science, Ophioplinthaca grandisquama n. sp., can be easily distinguished from its congeners by the distinctly elongated and stout tentacle scales, stout and long disc spines, capitate with typically elongate to flaring head bearing numerous distinct thorns, radial shields roughly triangular and contiguous distally. One specimen was identified as Ophioplinthaca semele (Clark, 1949), which had been reported in Hawaii seamounts, is a new record of this species in the Northwest Pacific. The remaining specimen was an unknown species of Ophioplinthaca, with some different characteristics from other species of Ophioplinthaca. However, we, herein, prefer not to attach a name to this specimen until more morphological characteristics are available. The finding of this new species and two new records further enriches the distribution of Ophioplinthaca in the seamount of Northwest Pacific, providing useful information for marine protection in the cobalt-rich area.

Spatial vision was recently reported in a brittle star, Ophiomastix wendtii, which lacks discrete eyes, but little is known about its visual ecology. Our aim was to better characterize the vision and visual ecology of this unusual visual system. We tested animal orientation relative to vertical bar stimuli at a range of angular widths and contrasts, to identify limits of angular and contrast detection. We also presented dynamic shadow stimuli, either looming towards or passing the animal overhead, to test for potential defensive responses. Finally, we presented animals lacking a single arm with a vertical bar stimulus known to elicit a response in intact animals. We found that O. wendtii orients to large (≥50 deg), high-contrast vertical bar stimuli, consistent with a shelter-seeking role and with photoreceptor acceptance angles estimated from morphology. We calculate poor optical sensitivity for individual photoreceptors, and predict dramatic oversampling for photoreceptor arrays. We also report responses to dark stimuli moving against a bright background – this is the first report of responses to moving stimuli in brittle stars and suggests additional defensive uses for vision in echinoderms. Finally, we found that animals missing a single arm orient less well to static stimuli, which requires further investigation., Summary: Brittle star responses to static visual stimuli of varying size and contrast show that visually guided habitat selection requires large, high-contrast stimuli. Responses to the appearance of overhead shadows reveal additional uses for photoreception in defensive behaviours.

Due to their peculiar and sometimes bizarre morphology, cave fauna (across invertebrates and vertebrates from both aquatic and terrestrial cave habitats) have fascinated researchers throughout history. Despite their success in colonizing most marine ecosystems, the adaptations of cave brittle stars (Ophiuroidea) to a stygobiotic lifestyle have been scarcely examined. Employing comparative methods on a data set of two species belonging to the genusOphionereis, this study addresses whether a cave-dwelling species from Cozumel exhibited similar troglomorphic traits as those of other taxa inhabiting caves. Our work demonstrated that some characters representing potential morphological cave adaptations inO. commutabiliswere: bigger sizes, elongation of arms and tube feet and the presence of traits potentially paedomorphic. In addition, an element of ophiuroid’s photoreceptor system, as well as pigmentation, was observed to be peculiar in this stygobiotic species, plausibly as a result of inhabiting a low light-energy environment. Finally, we add evidence to the statement thatO. commutabilisis a cave endemic species, already supported by demography, distribution and origin of this species, and now by a typical array of troglomorphisms.

[Figure][1] Bioluminescence produced by an Amphiura filiformis brittle star. Photo credit: ©J. Mallefet – FNRS, Universite Catholique de Louvain. Instead of blending in with their surroundings for safety, some brittle stars advertise their presence with bright pinpoints of light

Ophiothela mirabilis is native to the Pacific Ocean and has recently invaded the Caribbean and the southwestern Atlantic. In this study, using SCUBA diving techniques, we observed specimens of the invasive O. mirabilis in association with an octocoral host ( Leptogorgia punicea ) at the equatorial margin in the southwestern Atlantic (03°32′S, 38°47′W). We filled a gap of more than ~1,500 km between the Amazon reefs and the coast of Pernambuco State. The results indicate that O. mirabilis has invaded ~6,700 km of coastline in the southwestern Atlantic in the last 17 years. Moreover, our results support the hypothesis that the consistent color pattern of specimens from Brazil, French Guiana, Saint Vincent, and Tobago indicates the existence of a single lineage proliferating by asexual reproduction. Because the South Atlantic is the most recent of the oceans, as well as a hotspot for tropical biodiversity, much more information on invertebrate bioinvasions in this region is needed. Normal 0 21 false false false PT-BR X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

A new genus of ophiuroid, Luxaster n. gen., is described based on articulated skeletal remains preserved as external molds. The new genus belongs to the Paleozoic stem-group family Protasteridae. It includes two species, Luxaster martini n. sp. from the Lower Devonian of Luxemburg, and Luxaster schweitzeri from the Lower Devonian of W-Germany. Within the Protasteridae, Luxaster stands out in showing a combination of characters best interpreted as strongly paedomorphic within the morphological spectrum of the family. This suggests that paedomorphosis played a role in ophiuroid evolution not only in the living clades but also in the extinct stem groups.

Due to its unique geological location, the Bering Sea is an ideal place to investigate the water exchange and ecosystem connectivity of the Pacific Ocean–Arctic Ocean and subarctic–Arctic region. Based on a number of summer surveys (July to September, 2010, 2012 and 2014), macrobenthic communities and their spatial-temporal patterns are exhibited for the majority of the Bering Sea (53°59′–64°36′N). The results show that the macrobenthic communities were dominated by northern cold-water species and immigrant eurythermic species, and the communities assumed a dispersed and patchy distribution pattern. Polychaetes (Scoloplos armiger), crustaceans (Ceradocus capensis) and sea urchins (Echinarachnius parma) were the main dominant groups in the shallow shelves; the sea star (Ctenodiscus crispatus) and the brittle star (Ophiura sarsii) were the main dominant groups in the continental slope; whereas small polychaetes (Prionospio malmgreni) dominated the basin area. Sediment type, water depth, and currents were the major factors affecting the structure and spatial distribution of the macrobenthic communities. Compared with other seas, the shallow areas of the Bering Sea showed an extremely high-standing biomass. In particular, the northern shelf area (north of St. Lawrence Islands and west of 170°W), which is primarily controlled by Anadyr Water, is an undersea oasis. In contrast, a deficiency in the downward transport of particulate organic carbon has resulted in a desert-like seabed in the basin area. By comparing our results to previous studies, we found that macrobenthic communities of the Bering Sea have undergone significant structural changes in recent decades, resulting in a decrease in abundance and an increase in biomass. In addition, populations of amphipods and bivalves in the northern shelves have decreased significantly and have been gradually replaced by other species. These changes might be associated with advanced seasonal ice melting, changes in organic carbon input, and global warming, indicating that large-scale ecosystem changes have been occurring in the Bering Sea.

The brittle star Ophiothela mirabilis, thought to be confined to Pacific waters, was first observed in the Atlantic in 2000. Since then, it has expanded its range north to Trinidad and Tobago and south to Paraná, Brazil. By monitoring the coast of Santa Catarina, Brazil, with both recruitment plates in harbors and SCUBA diving, we were able to observe specimens of Ophiothela mirabilis in both natural and anthropogenic habitats. This presents a range extension of ~80 km south and emphasizes the importance of anthropogenic means for their spread and establishment.

Ophioconis claviculata sp. nov. is described on the basis of three specimens collected from Ryukyu Islands, southwestern, Japan. The new species is distinct in having: disc covered by granules; four, sometimes five flat, polygonal oral papillae on each side of jaw; broad and flat teeth with hyaline distal end; spiniform and conical arm spines, two times longer than the corresponding arm segment at the maximum length; oralmost arm spines on proximal portion of arms flattened and clavate; four tentacle scales on third tentacle pore; and ventral arm plate longer than wide, with concentrate lamellar striations. The new species was found under rocks of open water as well as in a dark and medium to low salinity (28 ppt) environment of submarine cave, suggesting that this species tolerate this specific condition.

The composition of common species in some macrozoobenthos groups that are considered as potential indicators of vulnerable marine ecosystems (VME), in the Anadyr Bay area, Bering Sea have been determined based on the results of four benthic surveys using a benthic grab sampler (1985, 2005) and a bottom trawl (2008, 2012). These are soft corals (Gersemia rubiformis), sponges (Myxilla incrustans, Halichondria panicea, and Semisuberites cribrosa), ascidians (Halocynthia aurantium and Boltenia ovifera), bryozoans (Cystisella saccata and Flustra foliacea), barnacles (Chirona evermanni), and the brittle star (Gorgonocephalus eucnemis). The distribution of these animals has been mapped. Aggregations of immobile sestonophages (the former five groups) are formed on hard coarse-grained and mixed sediments in waters with higher hydrodynamic activity (along the southwestern and northeastern coasts of the Anadyr Bay, mainly at depths of 80–90 m). In some cases, sponges and bryozoans in the southern part of the area can descend to a depth of 250 m (in the Navarin Canyon). The mobile filterer G. eucnemis forms aggregations mainly on soft sediments in the central part of Anadyr Bay, at depths of 50–270 m, in the area of a localized spot of near-bottom cold water. According to the results of trawl surveys conducted in 2008 and 2012, the mean biomass of the sponges, the brittle star G. eucnemis, and the sea squirt B. ovifera did not change, whereas the mean biomass of the barnacle Ch. evermanni and sea peach H. aurantium decreased by 6.5 and 3.7 times, respectively. Since the level of trawl fishing activity in the region is not high, the hypothesis has been proposed that the decrease in the abundance of the latter two species is presumably caused by the natural dynamics of their population or can be related to the factor of randomness, as these species are caught in their mosaically distributed local aggregations.

Marine intertidal regions are physically stressful habitats. In such an environment, facilitator species and positive interactions mitigate unfavorable conditions to the benefit of less tolerant organisms. In sponge–brittle star association, sponges effectively shelter brittle stars from biotic and abiotic stresses. The sponge, Biemna fortis (Topsent, 1897) was examined from two intertidal regions Anjuna and Mhapan along the Central West Coast of India for associated brittle star Ophiactis modesta (Brock, 1888) during 2013–2014. The study sites varied in suspended particulate matter (SPM). B. fortis at the high SPM habitat (Anjuna) had partially buried growth form and at the low SPM habitat (Mhapan) had massive growth form. O. modesta was abundantly associated with the massive growth form (50–259 individuals per 500 ml sponge) but rarely occurred in association with partially buried growth form (6–16 individuals per 500 ml sponge). In laboratory choice assay O. modesta showed equal preference to the chemical cues from both the growth forms of B. fortis. In addition, O. modesta showed significant preference to B. fortis compared to other sympatric sponges. These observations highlight the involvement of chemical cues in host recognition by O. modesta. Massive growth forms transplanted to the high SPM habitat were unable to survive but partially buried growth forms transplanted to the low SPM habitat were able to survive. Differential growth forms of the host sponge B. fortis at different abiotic stresses affect the abundance of the associated brittle star O. modesta.

Accepted manuscript version. Published version available in . https://doi.org/10.1016/j.csr.2017.03.011 Licensed CC BY-NC-ND 4.0. Dense brittle star assemblages dominate vast areas of the Arctic marine shelves, making them key components of Arctic ecosystem. This study is the first to determine the population dynamics of the dominant shelf brittle star species, Ophiura sarsii and Ophiocten sericeum, through age determination, individual production and total turnover rate (P:B). In the summer of 2013, O. sarsii were collected in the northeastern Chukchi Sea (depth 35–65 m), while O. sericeum were collected in the central Beaufort Sea (depth 37–200 m). Maximum age was higher for O. sarsii than for O. sericeum (27 and 20 years, respectively); however, both species live longer than temperate region congeners. Growth curves for both species had similar initial fast growth, with an inflection period followed by a second phase of fast growth. Predation avoidance in addition to changes in the allocation of energy may be the mechanisms responsible for the observed age dependent growth rates. Individual production was higher for O. sarsii than for O. sericeum by nearly an order of magnitude throughout the size spectra. The distinct distribution pattern of the two species in the Alaskan Arctic may be determined by environmental characteristics such as system productivity. Both species had equally low turnover rates (0.2 and 0.1, respectively), similar to Antarctic species, but lower than temperate species. Such characteristics suggest that the dense brittle star assemblages that characterize the Arctic shelf system could have a recovery time from disturbance on the order of decades.

Deception Island is an active volcano in Antarctic waters under high sedimentation regimes, which may affect the abundance and structure of soft-bottom assemblages. During the summer of 2012–2013, a survey of the shallow water soft-bottom assemblages of Deception Island was carried out to examine patterns of abundance and size structure of the three dominant echinoderms ( Ophionotus victoriae , Sterechinus neumayeri and Odontaster validus ) at 8 locations encompassing a gradient in proximity from the open ocean, including two depths (5 vs . 15 m) per location. Abundance patterns of the three species varied with depth; organisms were typically more abundant at 15 relative to 5 m depth. Our results partially supported the hypothesis that echinoderms from locations adjacent to the open ocean present larger abundances. Body sizes varied significantly among locations and depths for the three species and some places presented a density-size pattern. High sedimentation rates, combined with low ice-related disturbance, may be the reason behind the large abundances of echinoderms found in this waters.

The first morphological observation of a euryalid brittle star, Asteronyx loveni, using non-destructive X-ray micro-computed tomography (µCT) was performed. The body of euryalids is covered by thick skin, and it is very difficult to observe the ossicles without dissolving the skin. Computed tomography with micrometer resolution (approximately 4.5–15.4 µm) was used to construct 3D images of skeletal ossicles and soft tissues in the ophiuroid's body. Shape and positional arrangement of taxonomically important ossicles were clearly observed without any damage to the body. Detailed pathways inside the vertebral ossicles, lateral arm plates, and arm spines for passage of nerves and water vascular structures were observed. Inter-vertebral muscles were also observed. Forms and 3D arrangements of many important taxonomical characters of the euryalids were scrutinized by µCT in high enough resolution for taxonomic description of ophiuroids.

Bioluminescence is a widespread phenomenon in the marine environment. Among luminous substrates, coelenterazine is the most widespread luciferin, found in more than nine phyla. The wide phylogenetic coverage of this light-emitting molecule has led to the hypothesis of its dietary acquisition that was demonstrated in one cnidarian and one lophogastrid shrimp species so far. Within Ophiuroidea, the dominant class of luminous echinoderms, Amphiura filiformis is a model species known to use coelenterazine as substrate of a luciferin / luciferase luminous system. The aim of this study was to perform a long-term monitoring of A. filiformis luminescent capabilities during captivity. Our results show (i) depletion of luminescent capabilities within five months when the ophiuroid is fed with a coelenterazine-free diet and (ii) a quick recovery of luminescent capabilities when the ophiuroid is fed with coelenterazine-supplemented food. The present work demonstrates for the first time a trophic acquisition of coelenterazine in A. filiformis to maintain light emission capabilities.

The invasive brittle star Ophiothela mirabilis (family Ophiotrichidae), a tropical Indo-Pacific endemic species, first reported in Atlantic waters off southern Brazil in 2000, has extended its range northward to the Caribbean Sea, to the Lesser Antilles in 2011, and was first reported in south Florida in January 2019. Its occurrence in southeast Florida extends along nearly 70 km of coastline, from near the Port of Miami, Miami-Dade County, northward to Deerfield Beach, Broward County. It occurs abundantly as an epizoite on octocorals, attaining population densities of 25 individuals and more per 10-cm long octocoral stem. The surface texture of octocoral hosts (rough, smooth) did not affect the densities of the ophiuroid epizoites, and there were significantly greater abundances on octocorals during two winter sampling periods than in the summer. Beige and orange-coloured morphs are sometimes present on the same octocoral stem. Gut content analysis supported a suspension feeding mode, revealing essentially identical ingested items in both colour morphs with a preponderance of amorphous detritus and filamentous algae. Molecular genetic evidence (COI & 16s) has established the identity of O. mirabilis and its relationship to invasive Brazilian populations. The orange and beige morphs form two distinct, but closely related lineages that may represent two separate introductions. The orange morph shares haplotypes with Brazilian and Caribbean specimens suggesting a further range expansion of the ‘original’ invasion. The beige morph, however, shares haplotypes with specimens from the Mexican Pacific and Peru and potentially represents a secondary introduction. Traits promoting dispersal and establishment of this species in new habitats are manifold: vagility and ability to cling tightly to diverse host taxa (e.g. sponges, cnidarians, bryozoans, and echinoderms), frequent asexual reproduction (fissiparity), suspension feeding, including a wide range of dietary items, possession of integument-covered ossicles and arm spines offering protection from predators, and an effective competitive edge over associated microbiota for substrate space.

Published records on the Ophiuroidea fauna of the Persian Gulf and Gulf of Oman are scattered in difficult to access journals and books. This study presents a compilation of all published records, complemented with data from new samples. Distribution, habitat and depth in the study area, as well as known Indian Ocean distributions, are included. The taxonomic status of all species was evaluated, critical comments were added as applicable, and several previous records were reassigned to other species. Ophiocoma erinaceus was removed from the fauna of the Persian Gulf and Gulf of Oman, because the only published record was instead Ophiocoma schoenleinii. Previous studies assumed that 46 species of brittle star were known from the study area, but only 38 species were confirmed by this re-assessment, including two new records (Ophiothrix (Ophiothrix) foveolata and Ophiocomella sexradia). Diagnostic features are supplied for difficult to distinguish species. Five species (Macrophiothrix elongata, Amphiura fasciata, Amphiura (Ophiopeltis) hexactis, Amphioplus echinulatus, and Amphioplus seminudus) are so far worldwide known only from the Persian Gulf area. A hexamerous, fissiparous species of Ophiothela that does not concur with any known species was found and may represent a new species. All newly collected species are illustrated with photographs.

7 pages; International audience; Knowledge on the morphology of Early Triassic ophiuroids is very limited, in spite of the relatively high number of described species. This hampers attempts to use morphology-based phylogenetic analyses in order to explore the early diversification of the ophiuroid modern clades between the latest Paleozoic and the early Mesozoic. Here, a new ophiuroid from the Early Triassic of southern Idaho (USA) is described and assigned to the new taxon Shoshonura brayardi Thuy nov. gen., nov. sp. It is part of an exceptional Early Triassic faunal assemblage recently described as the Paris Biota. On account of the arm morphology and the shape of the arm spines and arm spine articulations, Shoshonura brayardi nov. gen., nov. sp. is considered a basal member of the suborder Ophiodermatina.

The Pacific epizoic brittle star Ophiothela mirabilis Verrill, 1867 has successfully established itself along the Southwestern Atlantic. While reports of this species show high densities and an expanding range throughout the Western Atlantic, specific knowledge regarding populations and their potential for distribution is scarce. We assess herein the current distribution and abundance patterns of O. mirabilis along the subtropical SW Atlantic coast while simultaneously employing ecological niche models (ENMs) to predict suitable habitats in the future. Ophiothela mirabilis is currently distributed in both poly- and euhaline estuarine and inner continental shelf areas. Population densities tend to increase from the inner shelf (≤ 492 individuals.m−2) to estuarine habitats (≥ 815 individuals.m−2), characterized by a 53.38% mean habitat suitability index, until being limited by unsuitable environmental habitats. Octocoral species are the most densely and frequently colonized hosts (up to 3.6 individuals.cm−2 of host's area). Currently, occurrence records for O. mirabilis encompass disjunct habitats from Santa Catarina (S Brazil) to Southeast Florida (USA). Our ENMs predicted that O. mirabilis has the potential to further spread across the warm marine provinces of the Western Atlantic, as they are characterized by ≥40.72% of environmentally suitable habitats. The occurrence of the species correlates mainly to mean calcite concentration and mean sea surface temperature, which accounts for 56.97% of the performance of the ENMs. The high spreading capacity and the maintenance of dense abundances on hosts raises questions about its effects on recipient biodiversity and systems.

To clarify the process of producing the striations in the trace fossil Asteriacites, we observed the behavior of living ophiuroids and asteroids in aquariums. When ophiuroids stopped crawling, they buried themselves shallowly in the substratum, removing substratum under their arms and discs by using their tube-feet. The basal-arm tube-feet produce well spaced, fine, parallel striations that are perpendicular to the arm axis. The oral tube-feet produce fine, radial striations in the central depression. When the ophiuroids resumed crawling, they raised their disc and four arms above the substratum and dragged one arm backward. The one backward arm erased the striations, and parallel fine striations remained in four arm depressions. Similarly, asteroids also produced wide and shallow striations perpendicular to the arm axis by tube-feet movement. When the asteroids started to move again, they bulldozed the substratum under the one preceding arm, where the striations were erased. Since the asteroids...

To determine the spatial resolution of sediment properties and benthic macrofauna communities in acoustic backscatter, the suitability of four acoustic seafloor classification devices (single-beam echosounder with RoxAnn and QTC 5.5 seafloor classification system, sidescan sonar with QTC Swathview seafloor classification, and multi-beam echosounder with QTC Swathview seafloor classification) was compared in a study area of approx. 6 km2 northwest of the island of Helgoland in the German Bight, southern North Sea. This was based on a simple similarity index between simultaneous sidescan sonar, single-beam echosounder and multi-beam echosounder profiling spanning the period 2011–2014. The results show a high similarity between seafloor classifications based on sidescan sonar and RoxAnn single-beam systems, in turn associated with a lower similarity for the multi-beam echosounder system. Analyses of surface sediment samples at 39 locations along four transects (0.1 m2 Van Veen grab) revealed the presence of sandy mud (southern and western parts), coarse sand, gravel and cobbles. Rock outcrops were identified in the north-eastern and eastern parts. A typical Nucula nitidosa–Abra alba community was found in sandy muds to muddy sands in the northern part, whereas the southern part is characterised by widespread occurrence of the ophiuroid brittle star Amphiura filiformis. A transitional N. nitidosa–A. filiformis community was detected in the central part. Moreover, the southern part is characterised by a high abundance of A. filiformis and its commensal bivalve Kurtiella bidentata. The high number of A. filiformis feeding arms (up to ca. 6,800 per m2) can largely explain the gentle change of backscatter intensity along the tracks, because sediment composition and/or seafloor structures showed no significant variability.

The population ecology of the sand dollar Sculpsitechinus auritus was studied in shallow coastal habitats of the Gulf of Suez, Egypt, from January 2013 to October 2014. Bimonthly sampling revealed that 95 % of the individuals had a width of 100–145 mm and that juveniles were absent throughout the sampling period. The mean gonadosomatic index (GSI) reached peaks of >2 % in September 2013 and August 2014, which concurred with seasonal highs of water temperature. Declining GSI values indicated that spawning took place between October and January. Histological examination of the gonads confirmed that spawning started in October. Locomotion rate was 88.7 mm h−1 in September, which was significantly higher than 56.3 mm h−1 in December. Similarly, water temperature was significantly higher in September (26 °C) than in December (17 °C), most probably explaining locomotion differences. Organic matter and grain size fractions of the sediment were not significantly different. Maximum density of 0.68 individuals m−2 was found at 4 m depth, whereas at other depths densities were significantly lower (≤0.05 individuals m−2). The epibiotic brittle star Ophiodaphne scripta was found on >67 % of the sand dollars and its frequency was significantly higher (>1.5 per host) between September and November coinciding with the onset of S. auritus’s spawning period.

A new species of brittle star,Ophiomitrella floorae, is recorded from the lower two meters of the Gronsveld Member (Maastricht Formation), of late Maastrichtian age (c. 66.7 Ma). These relatively fine-grained biocalcarenites reflect shallow-water deposition in a sheltered setting with a relatively firm sea floor and clear waters, under middle sublittoral and subtropical conditions. Associated echinoderm taxa comprise more robust, sturdy-plated ophiomusaid and ophiodermatid brittle stars and numerous bourgueticrinine sea lilies. The new brittle star described herein belongs to a family whose present-day members are predominantly restricted to bathyal depths. Its small size and the exceptional preservation of a single articulated specimen partially wrapped around the stalk of a bourgueticrinine suggest thatO. flooraen. sp. was probably epizoic and specifically associated with stalked crinoids.

Brittle stars (Phylum Echinodermata, Class Ophiuroidea) have evolved rapid locomotion employing muscle and skeletal elements within their (usually) five arms to apply forces in a manner analogous to that of vertebrates. Inferring the inner workings of the arm has been difficult as the skeleton is internal and many of the ossicles are sub-millimeter in size. Advances in 3D visualization and technology have made the study of movement in ophiuroids possible. We developed six virtual 3D skeletal models to demonstrate the potential range of motion of the main arm ossicles, known as vertebrae, and six virtual 3D skeletal models of non-vertebral ossicles. These models revealed the joint center and relative position of the arm ossicles during near-maximal range of motion. The models also provide a platform for the comparative evaluation of functional capabilities between disparate ophiuroid arm morphologies. We made observations on specimens of Ophioderma brevispina and Ophiothrix angulata. As these two taxa exemplify two major morphological categories of ophiuroid vertebrae, they provide a basis for an initial assessment of the functional consequences of these disparate vertebral morphologies. These models suggest potential differences in the structure of the intervertebral articulations in these two species, implying disparities in arm flexion mechanics. We also evaluated the differences in the range of motion between segments in the proximal and distal halves of the arm length in a specimen of O. brevispina, and found that the morphology of vertebrae in the distal portion of the arm allows for higher mobility than in the proximal portion. Our models of non-vertebral ossicles show that they rotate further in the direction of movement than the vertebrae themselves in order to accommodate arm flexion. These findings raise doubts over previous hypotheses regarding the functional consequences of ophiuroid arm disparity. Our study demonstrates the value of integrating experimental data and visualization of articulated structures when making functional interpretations instead of relying on observations of vertebral or segmental morphology alone. This methodological framework can be applied to other ophiuroid taxa to enable comparative functional analyses. It will also facilitate biomechanical analyses of other invertebrate groups to illuminate how appendage or locomotor function evolved.

Caves are a useful system for testing evolutionary and biogeographic hypotheses, as they are isolated, and their environmental conditions have resulted in adaptive selection across different taxa. Although in recent years many more cave species have been discovered, cave-dwelling members of the class Ophiuroidea (brittle stars) remain scarce. Out of the more than two thousand species of brittle stars described to date, only three are regarded as true cave-dwellers. These occurrences represent rare colonising events, compared to other groups that are known to have successfully diversified in these systems. A third species from an anchihaline cave system in the Yucatan Peninsula, Mexico, has been previously identified from cytochrome oxidase I (COI) barcodes. In this study, we reassess the species boundaries of this putative cave species using a phylogenomic dataset (20 specimens in 13 species, 100 exons, 18.7 kbp). We perform species delimitation analyses using robust full-coalescent methods for discovery and validation of hypotheses on species boundaries, as well as infer its phylogenetic relationships with species distributed in adjacent marine regions, in order to investigate the origin of this cave-adapted species. We assess which hypotheses on the origin of subterranean taxa can be applied to this species by taking into account its placement within the genus Ophionereis and its demographic history. We provide a detailed description of Ophionereis commutabilis n. sp., and evaluate its morphological characters in the light of its successful adaptation to life in caves.

Brittle stars are conspicuous members of benthic ecosystems, fill many ecological niches and are the most speciose of all classes of echinoderms. With high levels of biodiversity, elucidating the evolutionary history of this group is important. Understanding of higher-level relationships within Ophiuroidea has been aided by multilocus nuclear data and DNA barcoding. However, the degree of consistency between mitochondrial and nuclear data within ophiuroids remains unclear and deserves further assessment. In this study, 17 mitochondrial genomes spanning the taxonomic breadth of Ophiuroidea were utilized to explore evolutionary relationships through maximum likelihood analyses, Bayesian inference and comparative assessment of gene order. Our phylogenetic analyses, based on both nucleotide and amino acid residues, support recent findings based on multilocus nuclear data and morphology, in that the brittle star clades Ophintegrida and Euryophiurida were recovered as monophyletic with the latter comprising Euyalida, Ophiuridae and Ophiopyrgidae. Only three different arrangements of the 13 protein coding and 2 ribosomal RNA genes were observed. As expected, tRNA genes were more likely to have undergone rearrangement but the order of all 37 genes was found to be conserved in all sampled Euryalida and Ophiuridae. Both Euryalida and the clade comprised of Ophiuridae and Ophiopyrgidae, each had their own conserved rearrangement of protein coding genes and ribosomal genes, after divergence from their last common ancestor. Euryalida has a rearrangement of the two ribosomal RNA genes, rrnS and rrnL, in contrast to Ophiuridae and Ophiopyrgidae, which had an inversion of the genes nad1, nad2, and cob relative to Ophintegrida. Further, our data support the gene order found in all sampled Euryalida as the most likely ancestral order for all Ophiuroidea.

Articulated brittle stars are rare fossils because the skeleton rapidly disintegrates after death and only fossilises intact under special conditions. Here, we describe an extraordinary mass occurrence of the ophiacanthid ophiuroid Brezinacantha tolis gen. et sp. nov., preserved as articulated skeletons from an upper Campanian (Late Cretaceous) methane seep of South Dakota. It is uniquely the first fossil case of a seep-associated ophiuroid. The articulated skeletons overlie centimeter-thick accumulations of dissociated skeletal parts, suggesting lifetime densities of approximately 1000 individuals per m2, persisting at that particular location for several generations. The ophiuroid skeletons on top of the occurrence were preserved intact most probably because of increased methane seepage, killing the individuals and inducing rapid cementation, rather than due to storm-induced burial or slumping. The mass occurrence described herein is an unambiguous case of an autochthonous, dense ophiuroid community that persisted at a particular spot for some time. Thus, it represents a true fossil equivalent of a recent ophiuroid dense bed, unlike other cases that were used in the past to substantiate the claim of a mid-Mesozoic predation-induced decline of ophiuroid dense beds.

A revision of the genus Astrodendrum Döderlein (Ophiuroidea, Euryalida, Gorgonocephalidae) is based on 14 specimens, including the holotypes of Astrodendrum galapagense A. H. Clark and Astroconus capense Mortensen and a syntype of Gorgonocephalus sagaminus Döderlein. A new species Astrodendrum spinulosum is described from the Pacific coast of Japan. It is distinguished from its congeners in having conical external ossicles on aboral side of the disc; bulges on lateral edges of proximal arms; 1 terminal projection on each arm spine of proximal portion of the arm; 2 or 3 secondary teeth on each hook-shaped arm spine of distal portion of the arm. A taxonomic key to all six species of the genus Astrodendrum is provided.

Echinoderm pluteus larvae are considered a classical example of convergent evolution that occurred in sea urchins and brittle stars. Several genes are known to be involved in the development of pluteus arms in sea urchins, including fgfA, pax2/5/8, pea3, otp, wnt5, and tet. To determine whether the convergent evolution of larval arms also involves these genes in brittle stars, their expression patterns were determined in brittle star. We found that all genes showed similar expression in the arms of ophiopluteus to that seen in echinopluteus, suggesting that convergent evolution of pluteus arms occurred by recruitment of a similar set of genes. This may be explained by our observation that some of these genes are also expressed in the spine rudiment of direct-type development sea urchins. We propose an evolutionary scenario wherein the pluteus arms of both echinopluteus and ophiopluteus were acquired by independent co-options of the genetic module responsible for the projection of the adult skeleton.

Two new species, Ophiolepis cavitata n. sp. and Ophiozonella cavernalis n. sp., are described from the specimens collected in shallow water submarine caves in the Ryukyu Islands, southwestern Japan. Ophiolepis cavitata n. sp. is distinguished from the other congeners in having prominent tubercle-shaped knobs on dorsal arm plates; two sizes of disc scales on the aboral disc, the larger surrounded by 3–8 times smaller disc scales; larger scales concave; radial shields wider than long; a trio of distinct scales present distal to each pair of radial shields; oral shields partly concave; 3 arm spines on proximal portion of the arms. Ophiozonella cavernalis n. sp. is distinguished from the other congeners in having polygonal, uniform size disc scales; oral shields almost as long as wide, shallow concave proximal sides that end in a fairly sharp point medially; arms about 9 times longer than disc diameter; 3 cylindrical arm spines, of which the oral most one is slightly larger than other 2 spines. Ophiozonella cavernalis n. sp. is the second finding of an anchialine-endemic ophiuroid and the first finding from the Pacific Ocean.

Ophiuroidea constitutes the largest class of the phylum Echinodermata. It includes families with suspension-feeder behaviour that can be found in dense aggregations in all oceans worldwide. Ophiothrix maculata was known as a rare suspension-feeder brittle star, with only four records in the Eastern Central Atlantic dating from almost 100 years ago. During the ten multidisciplinary Spanish and Norwegian surveys carried out from 2004 to 2012 off Northwest Africa, between the Gibraltar Strait and the Sierra Leone border from 19 to 1888 m depth, we sampled 1298 stations. We gathered about one million individuals and 124 kg of brittle stars at 501 of the stations. Eight hundred and thirty-two specimens of Ophiothrix maculata were collected at six localities on the continental slope off Mauritania, Western Sahara and Guinea Bissau, at depths between 155 and 594 m. The Guinea Bissau samples represent the southernmost current record for the species. Even though Ophiothrix maculata has been previously recorded only in isolation, we discovered dense concentrations on the Mauritanian slope on the Wolof's Seamount (580 individuals) and off the Western Sahara, in a Lophelia pertusa reef (202 individuals). In this paper, we describe these findings and discuss the association of this species to hard-bottom habitats and high primary production areas, outside of the oxygen minimum zone (OMZ). We also analyse what other factors may explain the patchy distribution of O. maculata on the Northwest African slope, Sí

In spite of increasing naval activities and petroleum exploration in cold environments, there is currently a paucity of tools available to monitor oil contamination in boreal marine life, especially in sedentary (non-fish) species that dominate benthic communities. This research aimed to identify biotic sources of variation in biomarkers using subarctic echinoderms, and to identify suitable biomarkers of their exposure to hydrocarbons. The focal species included the sea star Asterias rubens, the brittle star Ophiopholis aculeata, the sea urchin Strongylocentrotus droebachiensis, and the sea cucumber Cucumaria frondosa, which are among the most abundant echinoderms in the North Atlantic and Arctic Oceans. The latter two species are also commercially exploited. A series of 96-h acute exposures of the water-accommodating fraction (WAF) of used lubricating oil (ULO) were performed in different seasons (i.e. distinct reproductive stages). Digestive and reproductive tissues were analyzed for baseline and response levels of glutathione peroxidase (GPx) and ethoxyresorufin-O-deethylase (EROD). GPx activity was detected in the pyloric caecum, stomach, and gonad of sea stars, the intestine and gonad of sea cucumbers, and the gonad of brittle stars and sea urchins. No seasonal variation in baseline GPx activity occurred. Upon exposure to the ULO WAF, sex-based differences were elicited in the GPx activity of sea star stomachs (lower in females than males). EROD activity was present in the pyloric caeca of sea stars, and the gonads of brittle stars and sea urchins. An interaction between season and sex on baseline EROD activity was measured in the gonads of sea urchins. Ovaries exhibited significant seasonal variation in EROD activity and had greater activity than testes during the spawning and post-spawning seasons. Seasonal variation in EROD activity also occurred in sea star pyloric caeca and brittle star gonads. Furthermore, testes of sea urchins exposed to the ULO WAF exhibited suppressed EROD activity compared to baseline levels. The nearly universal presence of GPx activity highlights its potential as a useful biomarker, while EROD activity was much more limited. Findings suggest a complex relationship between temporal and biotic factors on both the baseline and response levels of enzymatic activity, emphasizing the need to consider sex and sampling season in studies of biomarkers of hydrocarbon exposure in boreal indicator species that display annual reproductive cycles.

The Antarctic Polar Front (APF) is one of the most well-defined and persistent oceanographic features on the planet and serves as a barrier to dispersal between the Southern Ocean and lower latitudes. High levels of endemism in the Southern Ocean have been attributed to this barrier, whereas the accompanying Antarctic Circumpolar Current (ACC) likely promotes west-to-east dispersal. Previous phylogeographic work on the brittle star Astrotoma agassizii Lyman, 1875 based on mitochondrial genes suggested isolation across the APF, even though populations in both South American waters and the Southern Ocean are morphologically indistinguishable. Here, we revisit this finding using a high-resolution 2b-RAD (restriction-site-associated DNA) single-nucleotide polymorphism (SNP)-based approach, in addition to enlarged mitochondrial DNA data sets (16S rDNA, COI, and COII), for comparison to previous work. In total, 955 biallelic SNP loci confirmed the existence of strongly divergent populations on either side of the Drake Passage. Interestingly, genetic admixture was detected between South America and the Southern Ocean in five individuals on both sides of the APF, revealing evidence of recent or ongoing genetic contact. We also identified two differentiated populations on the Patagonian Shelf with six admixed individuals from these two populations. These findings suggest that the APF is a strong but imperfect barrier. Fluctuations in location and strength of the APF and ACC due to climate shifts may have profound consequences for levels of admixture or endemism in this region of the world.

We describe a new species of sexually dimorphic brittle star, Ophiodaphne spinosa, from Japan associated with the irregular sea urchin, Clypeaster japonicus based on its external morphology, and phylogenetic analyses of mitochondrial COI (cytochrome c oxidase subunit I). Females of this new species of Ophiodaphne are characterized mainly by the presence of wavy grooves on the surface of the radial shields, needle-like thorns on the oral skeletal jaw structures, and a low length-to-width ratio of the jaw angle in comparison with those of type specimens of its Ophiodaphne congeners: O. scripta, O. materna, and O. formata. A tabular key to the species characteristics of Ophiodaphne is provided. Phylogenetic analyses indicate that the new species of Ophiodaphne, O. scripta, and O. formata are monophyletic. Our results indicate that the Japanese Ophiodaphne include both the new species and O. scripta, and that there are four Ophiodaphne species of sexually dimorphic brittle stars with androphorous habit.

The reproduction of the brittle star Astrotoma agassizii was studied from deep waters of the South Atlantic Ocean, based on samples collected in August 2012, and May and September 2013. Ten samples from 800 to 1400 m depths off Mar del Plata Canyon were studied. The species was found to be a brooding simultaneous hermaphrodite. Hermaphroditic gonads contained testis and ovaries inside the same sacs. Both, ovary and testis contained different stages of gametogenesis development simultaneously. The largest oocyte recorded was 800 µm diameter. Gonads contained several stages of oocytes in different stages of gametogenesis. Free spermatozoa were observed in the lumen of the testis, together with spermatogenic columns. Five individuals, from a total of 30 examined, resulted brooding, and most contained mature ovotestis at the same time. Incubation occurs in five of the ten bursal sacs, containing 15 to 20 young juveniles each. Maximum disc diameter recorded for a brood was 1120 µm. Herein we hypothesize that Astrotoma agassizii could be continuous breeder species in the deep-sea. Fil: Berecoechea, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Brogger, Martin Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Penchaszadeh, Pablo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina

Ophioderma cinerea (Muller & Troschel, 1842) is a species of warm water ophiuroid that lives primarily in rocky habitats in the tropical Atlantic. Competition for resources can be high in their habitat. Behavioral observations in aquaria led to a hypothesis that differences in body size may affect feeding strategies, and thus affect survivorship. It is widely accepted that echinoderm ontogenic growth is sigmoidal, with juveniles growing much faster than adults. Yet, it is not understood what affect this has on behavior. Individuals were kept in replicate experimental tanks. After a 3-d starvation period, each individual was exposed to a proteinaceous food stimulus. The animals were observed and a time measurement was taken to determine how long it took the animals to sense the food and to begin moving toward the food during both day and night. Smaller individuals were found to sense food significantly faster than larger ones, while no difference was observed for time-to-motion. Several explanations may support this finding. One of these explanations highlights how the need to compete with larger animals may have selectively adapted ontogenetically more sensitive chemoreceptors in smaller animals.

The small new brittle star Amphipholis conolampadis sp. nov. is reported from semi-infaunal cassiduloid echinoids Conolampas diomedeae collected at 75–300 m water depth at two sites in the Philippines. The ophiuroids show a preference to attach to the oral side of the echinoids, clustering in the region around the mouth. Orientation of the brittle stars, in contrast, seems to be random and ophiuroids appear to use echinoid spines for anchoring on the host. Neither detrimental effects could be observed in the sea urchins, nor do echinoid specimens bearing ophiuroids show differences in growth or size range. Clear evidence for a parasitic nature of the association is thus missing. Evidence for mutualism and commensalism is likewise weak, but seems more likely than parasitism. A review of echinoid–ophiuroid associations reported in the literature shows a strong dominance of amphiurids, associated mainly with irregular echinoids.

Embargo until 22 July 2019 Effects of water-based drill cuttings on sediment reworking activity were studied on two important benthic bioturbators (the bivalve Abra segmentum and the brittle star Amphiura filiformis) using thin aquaria, fluorescentdyed sediment particles (luminophores), time lapse photography and image analysis. In the present context, sediment reworking activity was measured as maximum mixing depth and total amount of luminophores transported below the sediment-water interface. There was a significant reduction in the amount of downward transported luminophores in drill cuttings treatments compared to controls with added natural sediments for both species, which also was true regarding maximum mixing depth for A. segmentum. Further, A. filiformis showed a clearly delayed burrowing of luminophores in the drill cuttings treatment compared to control. To conclude, the study showed that water-based drill cuttings have the potential to reduce sediment reworking. Further, it is evidenced that water-based drill cuttings not only cause burial effects.