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Flexible resource investment is a risk sensitive reproductive strategy where individuals trade resources spent on reproduction for basic metabolic maintenance and survival. This study examined morphological variation in herbivorous sea urchin grazers across a mosaic landscape of macroalgae dominated habitats interspersed with patches of sea urchin barrens to determine whether sea urchins shift energy allocation in response to food limitation. Extensive underwater surveys of habitat attributes (e.g., sea urchin density, algae cover) were paired with detailed laboratory assays (e.g., sea urchin dissections) to determine how resource abundance affects energy allocation between reproductive capacity and body structure in the purple sea urchin, Strongylocentrotus purpuratus. We found that: (1) sea urchins had a more elongate jaw structure relative to body size in habitats void of macroalgae (i.e., barrens), (2) sea urchin reproductive capacity (i.e., gonad index) was lower in barrens and the barrens habitat was primarily comprised of encrusting algae, and (3) sea urchin jaw morphology (i.e., lantern index) and reproductive capacity (i.e., gonad index) were inversely related. These results suggest that sea urchins respond to macroalgae limited environments by shifting energy allocation between reproductive capacity and modifications of the foraging apparatus, which may explain the ability of sea urchins to acquire food in resource-limited environments. [ABSTRACT FROM AUTHOR]

Sea urchins have a wide variety of symbionts on their body surfaces and inside their bodies. Copepods of the genus Clavisodalis (Taeniacanthidae) collected from the esophagus of sea urchins of the genera Diadema and Echinothrix in southern Japan were identified based on their morphological characteristics, and molecular analysis was conducted to determine whether genetic variation occurs in copepods from different localities and hosts. Morphological observations identified individuals from southern Japan as Clavisodalis sentifer Dojiri and Humes, 1982, making this the first record of this species in the northern hemisphere and the first record of its genus in Japan. Morphological and molecular analysis suggested that the copepod specimens collected from multiple hosts across two genera would be the same species. Considering the typically observed high level of host specificity among taeniacanthid copepods, the utilization of hosts from two genera by C. sentifer is noteworthy.

Because of their lifestyles, abundance, and feeding habits, infaunal marine deposit feeders have a significant impact on the ocean floor. As these animals also ingest microorganisms associated with their sediment and seawater diet, their digestive tract usually contains a diverse array of bacteria. However, while most of these microorganisms are transients, some may become part of a resident gut microbiome, in particular when sheltered from the main flow of digesta in specialized gut compartments. Here, we provide an in-depth analysis of the structure and contents of the intestinal caecum (IC), a hindgut diverticulum found exclusively in schizasterid heart urchins (Echinoidea: Spatangoida: Schizasteridae). Based on specimens of Brisaster townsendi, in addition to various other schizasterid taxa, our structural characterization of the IC shows that the organ is a highly specialized gut compartment with unique structural properties. Next generation sequencing shows that the IC contains a microbial population composed predominantly of Bacteroidales, Desulfobacterales, and Spirochaetales. The microbiome of this gut compartment is significantly different in composition and lower in diversity than the microbial population in the sediment-filled main digestive tract. Inferences on the function and evolution of the IC and its microbiome suggest that this symbiosis plays a distinct role in host nutrition and that it evolved at least 66 million years ago during the final phase of the Mesozoic.

In this paper we present the first record of well preserved specimens of Gitolampas subrotundus (Cotteau, 1856) from the Late Paleocene of Iran (Jorasan Razavi county, northeast Iran). the detailed biostratigraphic and calcareous nannofossils investigations were carried out on a stratigraphic section in Chehel Formation. this study extends the palaeogeographical distribution of Late Paleocene echinids along the northern tethyanmargins. the investigated fossiliferous section is compared with coeval strata from other european regions.

Abstract Background Echinoidea is a clade of marine animals including sea urchins, heart urchins, sand dollars and sea biscuits. Found in benthic habitats across all latitudes, echinoids are key components of marine communities such as coral reefs and kelp forests. A little over 1000 species inhabit the oceans today, a diversity that traces its roots back at least to the Permian. Although much effort has been devoted to elucidating the echinoid tree of life using a variety of morphological data, molecular attempts have relied on only a handful of genes. Both of these approaches have had limited success at resolving the deepest nodes of the tree, and their disagreement over the positions of a number of clades remains unresolved. Results We performed de novo sequencing and assembly of 17 transcriptomes to complement available genomic resources of sea urchins and produce the first phylogenomic analysis of the clade. Multiple methods of probabilistic inference recovered identical topologies, with virtually all nodes showing maximum support. In contrast, the coalescent-based method ASTRAL-II resolved one node differently, a result apparently driven by gene tree error induced by evolutionary rate heterogeneity. Regardless of the method employed, our phylogenetic structure deviates from the currently accepted classification of echinoids, with neither Acroechinoidea (all euechinoids except echinothurioids), nor Clypeasteroida (sand dollars and sea biscuits) being monophyletic as currently defined. We show that phylogenetic signal for novel resolutions of these lineages is strong and distributed throughout the genome, and fail to recover systematic biases as drivers of our results. Conclusions Our investigation substantially augments the molecular resources available for sea urchins, providing the first transcriptomes for many of its main lineages. Using this expanded genomic dataset, we resolve the position of several clades in agreement with early molecular analyses but in disagreement with morphological data. Our efforts settle multiple phylogenetic uncertainties, including the position of the enigmatic deep-sea echinothurioids and the identity of the sister clade to sand dollars. We offer a detailed assessment of evolutionary scenarios that could reconcile our findings with morphological evidence, opening up new lines of research into the development and evolutionary history of this ancient clade.

Abstract Background In Metazoa, mitochondrial markers are the most commonly used targets for inferring species-level molecular phylogenies due to their extremely low rate of recombination, maternal inheritance, ease of use and fast substitution rate in comparison to nuclear DNA. The mitochondrial control region (CR) is the main non-coding area of the mitochondrial genome and contains the mitochondrial origin of replication and transcription. While sequences of the cytochrome oxidase subunit 1 (COI) and 16S rRNA genes are the prime mitochondrial markers in phylogenetic studies, the highly variable CR is typically ignored and not targeted in such analyses. However, the higher substitution rate of the CR can be harnessed to infer the phylogeny of closely related species, and the use of a non-coding region alleviates biases resulting from both directional and purifying selection. Additionally, complete mitochondrial genome assemblies utilizing next generation sequencing (NGS) data often show exceptionally low coverage at specific regions, including the CR. This can only be resolved by targeted sequencing of this region. Results Here we provide novel sequence data for the echinoid mitochondrial control region in over 40 species across the echinoid phylogenetic tree. We demonstrate the advantages of directly targeting the CR and adjacent tRNAs to facilitate complementing low coverage NGS data from complete mitochondrial genome assemblies. Finally, we test the performance of this region as a phylogenetic marker both in the lab and in phylogenetic analyses, and demonstrate its superior performance over the other available mitochondrial markers in echinoids. Conclusions Our target region of the mitochondrial CR (1) facilitates the first thorough investigation of this region across a wide range of echinoid taxa, (2) provides a tool for complementing missing data in NGS experiments, and (3) identifies the CR as a powerful, novel marker for phylogenetic inference in echinoids due to its high variability, lack of selection, and high compatibility across the entire class, outperforming conventional mitochondrial markers.

Sea urchins is the member of Echinoidea. This species can be found in tropical marine water to the poles. The study aimed to know the types, the abundance and spread of sea urchins in Bengkayang Regency. The research, used the transect method. Each station consisted of 3 transects with a length of 50 meters from the shore into the sea with the distance of 10 meters among the transects. This research obtained five species consisting of three species of the Diadema (genus) and two species of the Echinotrix (genus) i.e. Diadema antillarium, D. savignyi, D. setosum, Echinotrix calamaris and E. deadema. The density of sea urchins in Lemukutan Island ranges from 273 – 453 ind/Ha. The Density of sea urchins on Penata Kecil island ranges from 167 - 347 ind / Ha and on Penata Besar Island has a range from 307 - 387 ind/Ha. The highest diversity of sea urchins was found in Penata Kecil Island of (1.2355). The distribution of sea urchins in Lemukutan and Penata Besar Island was categorized into clumped and evenly distributed, while the distribution of sea urchin on Penata Kecil Island is included in the clustered and random categories. Distribution of sea urchins on the island is influenced by several factors such as sea water waves and food contained in the environment.

Introduction: Embryonic and larval development in sea urchins is highly dependent on maternal nutritional status and on the environmental conditions of the seawater. Objective: To compare the development of Arbacia dufresnii in two different water temperatures and in progeny with varying maternal origins. Methods: We induced A. dufresnii females and males from Nuevo Gulf to spawn, collected the eggs of each female individually (progeny), separated them into two seawater temperatures (12 and 17 °C), and fertilized them. We recorded the percentage of fertilized eggs and embryos per developmental stage according to time, temperature and progeny. We measured larval growth by total length (TL) and midline body length (M) according to time post fecundation (DPF), temperature, and progeny. Results: Temperature did not affect fertilization, but embryo development was faster and more synchronized in the high temperature treatment. The generalized linear models indicate that embryo development depends on a quadruple interaction between the embryonic stage, time (h), seawater temperature and progeny. Larval growth was faster, producing larger larvae at the highest temperature. Larval growth depends on a triple interaction between time (DPF), seawater temperature and progeny. Conclusions: We found a temperature and progeny impact during embryonic and larval development and, in both cases, these factors generate a synergistic effect on developmental timing and larval size. This probably provides a survival advantage as a more rapid speed of development implies a decrease in the time spent in the water column, where the sea urchins are vulnerable to biotic and abiotic stressors. [ABSTRACT FROM AUTHOR]

Introduction: Sea urchin gonads (roe or uni) are considered a culinary delicacy worldwide. However, only a few species are considered edible and commercialized. The sea urchin Tripneustes depressus has generated the interest of producers in Baja California Sur, Mexico, due to the quality of its gonads. A biological basis for designing a management strategy is key to consider its commercial exploitation. Objective: To determine the reproductive season of T. depressus through description of the gonad stages and reproductive cycle, and to establish its relationship with environmental factors. Methods: We collected monthly samples (October 2016-September 2017), recording in-situ temperature and photoperiod. We evaluated a sample of 1 055 specimens for demographic characteristics, using total weight (g) and test diameter (cm). We also did a histological analysis of gonads from 178 individuals. Results: Average test diameter was 9.70 ± 0.03 cm (5-12.50 cm). Based on the proportion into the gonad of sexual (gametes) and somatic (nutritive phagocytes) cells, we propose five gonad stages (growing, premature, mature, spawning, and intergametic) for both sexes. There were two times of the year when gonads were heaviest and closely corresponded to the growing stage, coinciding with the highest proportions of nutritive phagocytes. Gonad development (growing and premature stages) peaks in the months with the longest daylight periods, with spawning in the shortest daylight periods. Conclusions: Gonad wet weight and adjusted gonad weight are good indicators of the reproductive season of T. depressus. The lowest gonad wet weights were matched the spawning peak in the shortest daylight period (January and March). [ABSTRACT FROM AUTHOR]

Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: "Iheringiella" sp. A is restricted to the late Oligocene, the genera Camachoaster and "Eoscutella" and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previ- ously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed "Monophoraster and Venericor Beds". Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages. [ABSTRACT FROM AUTHOR]

A fossil echinoid recently collected in the Langhian Pantano Formation at Santa Maria Villiana, in the Bologna Apennines (northern Italy), is here attributed to the Cyclaster genus Cotteau in Leymerie & Cotteau, 1856. The generic attribution is supported by the short, sunken paired petals, the faint anterior sulcus and the large bilobed subanal fasciole. Additionally, the oral plating scheme is very characteristic and shows a very long narrow labial plate. The preservation of the specimen did not enable the classification at a specific level, however the specimen is close to C. archeri from the late Oligocene-early Miocene of Southern Australia. Since the citations of Cyclaster from the early Miocene onward are limited to the Indo-Pacific area, the specimen from Santa Maria Villiana represents the latest occurrence of this genus in Europe so far before the final closure of contacts with the Indo-Pacific area. [ABSTRACT FROM AUTHOR]

Because of their lifestyles, abundance, and feeding habits, infaunal marine deposit feeders have a significant impact on the ocean floor. As these animals also ingest microorganisms associated with their sediment and seawater diet, their digestive tract usually contains a diverse array of bacteria. However, while most of these microorganisms are transients, some may become part of a resident gut microbiome, in particular when sheltered from the main flow of digesta in specialized gut compartments. Here, we provide an in-depth analysis of the structure and contents of the intestinal caecum (IC), a hindgut diverticulum found exclusively in schizasterid heart urchins (Echinoidea: Spatangoida: Schizasteridae). Based on specimens of Brisaster townsendi , in addition to various other schizasterid taxa, our structural characterization of the IC shows that the organ is a highly specialized gut compartment with unique structural properties. Next generation sequencing shows that the IC contains a microbial population composed predominantly of Bacteroidales, Desulfobacterales, and Spirochaetales. The microbiome of this gut compartment is significantly different in composition and lower in diversity than the microbial population in the sediment-filled main digestive tract. Inferences on the function and evolution of the IC and its microbiome suggest that this symbiosis plays a distinct role in host nutrition and that it evolved at least 66 million years ago during the final phase of the Mesozoic. [ABSTRACT FROM AUTHOR]

The functional diversity of echinoderms has been understudied, even though these organisms are critical components of various ecosystems, including coral reefs and hard-bottom benthic communities. Additionally, there are only a few papers relating the protection level of marine protected areas (MPAs) with functional diversity. In this study, we calculate the functional diversity of echinoids and asteroids in 11 coral and rocky reefs with different protection levels across the Mexican Pacific. We recorded the abundance of 15 echinoderm species comprising seven echinoid and eight asteroid species. More than 30 morphological and ecological traits of the censused species were evaluated to calculate two functional diversity indices: Rao's quadratic entropy index (FDQ) and functional richness (FRic). Latitudinal patterns of functional diversity differed between groups. Asteroids showed the highest FDQ and FRic values in the Gulf of California. Echinoids showed FDQ peaks at the highest (Bahía de los Ángeles; 28° 56′, − 113° 30′), and the lowest latitude (Bahías de Huatulco; 15° 43′, − 98° 08′) sites. The Ixtapa-Zihuatanejo site (17° 39′, − 101° 36′) had the highest FRic values. Generalized linear mixed models showed that protection level did not have any significant effect on FDQ or FRic. Latitude, on the other hand, did have a significant effect on asteroid functional diversity, although no significant effects were found for echinoids. The lack of an effect of protection level, and the support of a latitudinal gradient in terms of both taxonomic and functional diversity, has important implications for conservation efforts, supporting the idea of a protected area network to maintain adequate regional biodiversity. [ABSTRACT FROM AUTHOR]

Clypeasteroid echinoids are widespread and abundant within Miocene sedimentary sequences of the Mediterranean area within both siliciclastic and carbonate deposits. Herein, three clypeasteroid-dominated echinoid assemblages from the mixed siliciclastic-carbonate succession of the Mores Formation (lower Miocene) cropping out within the Porto Torres Basin (northern Sardinia) are described. These assemblages were compared to previously described clypeasteroid-bearing deposits from the Miocene of northern Sardinia with the purpose of investigating their palaeoecology and taphonomy along a shelf gradient. These goals are accomplished by various methods including (i) logging sedimentary facies, (ii) analysing the functional morphology of sea urchin skeletons, (iii) comparing the relative abundance of taxa and taphonomic features, and (iv) studying associated fauna, flora, and trace fossils. The clypeasteroid-bearing deposits differ greatly with respect to echinoid diversity, accompanying fauna and flora, sedimentological signatures, and taphonomic features. They also show variations in depositional environments and the mechanism of formation of the deposits. Three different shelf settings are distinguished: littoral, inner sublittoral, and outer sublittoral environments. Furthermore, an ecomorphological gradient along the shelf is recognized with respect to echinoid taxa and their morphologies. This gradient ranges from shallow water to a moderately deep shelf and is interpreted with respect to both abiotic and biotic factors as well as the taphonomy of the echinoid tests.

Rocky reefs of the northern Colombian Pacific (Chocó) are diverse ecosystems that are poorly studied. Echinoderms are one of the principal groups in these ecosystems with associations to different species, including benthic organisms in which they live and other species that use them as hosts. These relationships include fishes, sponges, seaweeds, cnidarians, polychaetes, bryozoans, crustaceans, mollusks, and other echinoderms. For this area, 22 associations were registered, including commensalism, epibionts and parasitism. This work constitutes the first report for the associations of Eucidaris thouarsii with Suberites aff. ficus, E. thouarsii with Ophiothela mirabilis, and Holothuria (Thymiosicia) impatiens with Encheliophis vermicularis. Associations of Pentaceraster cumingi with Zenopontonia soror, and Ophionereis annulata with Malmgreniella cf. variegata are new records for Colombia. This work also expands the range of hosts previously described for Ophiothela mirabilis and expands the distribution of the association between Diadema mexicanum and Echineulima cf. robusta. [ABSTRACT FROM AUTHOR]

A new parasitic species of eulimid gastropod, Haliella seisuimaruae sp. nov., is described from bathyal (728-978 m) waters off the Pacific coasts of Japan. It shows the closest resemblance to the type species H. stenostoma from the North Atlantic and Barents Sea in having a tall shell with an almost straight outer lip, but differs in having a junction of the parietal wall and columellar lip at 38% of the aperture height from the suture (33% in H. stenostoma), a slightly wider aperture and a more curved and extended columellar lip. The holotype of H. seisuimaruae sp. nov. was found attached to an irregular sea urchin, Brissopsis sp. cf. luzonica (Spatangoida: Brissidae). This represents the first direct observation of parasitic ecology and echinoderm host for the genus Haliella. A new replacement name, Eulima tsushimensis nom. nov., is proposed here for Eulima stenostoma A. Adams, 1861, which is preoccupied by Eulima stenostoma Jeffreys, 1858 (type of Haliella). [ABSTRACT FROM AUTHOR]

A new rhabdocoel of the genus Syndesmis Silliman, 1881 (Umagillidae) is described from the intestine of the New Zealand sea urchin Evechinus chloroticus (Valenciennes, 1846) Mortensen, 1943a. This new species, Syndesmis kurakaikina n. sp., is morphologically distinct and can easily be recognised by its very long (±1 mm) stylet and its bright-red colour. In addition to providing a formal description, we present some observations on reproduction and life history of this new species. Fecundity is comparable to that of other umagillids and the rate of egg production and development increases with temperature. Hatching in this species is induced by intestinal fluids of its host. Relevant to global warming, we assessed the effect of temperature on survival, fecundity, and development. The tests indicate that Syndesmis kurakaikina n. sp. is tolerant of a wide range of temperatures (11–25 °C) and that its temperature optimum lies between 18.0 and 21.5 °C. Egg viability is, however, significantly compromised at the higher end of this temperature range, with expelled egg capsules often being deformed and showing increasingly lower rates of hatching. Given this, a rise in global temperature might increase the risk of Syndesmis kurakaikina n. sp. infecting new hosts and would possibly facilitate the spread of these endosymbionts. Image 1 • Syndesmis kurakaikina n. sp. (Umagillidae, Rhabdocoela) is described. • This new species was found infecting kina (Evechinus chloroticus) in New Zealand. • S. kurakaikina n. sp. can tolerate a wide range of temperatures. • Egg-capsule production and development increase with temperature. • Rising sea-water temperatures may facilitate infection and spread of this species. [ABSTRACT FROM AUTHOR]

Inclusion of fossils can be crucial to address evolutionary questions, because their unique morphology, often drastically modified in recent species, can improve phylogenetic resolution. We performed a cladistic analysis of 45 cassidulids with 98 characters, which resulted in 24 most parsimonious trees. The strict consensus recovers three major cassiduloid clades, and the monophyly of the family Cassidulidae is not supported. Ancillary analyses to determine the sensitivity of the phylogeny to missing data do not result in significantly different topologies. The taxonomic implications of these results, including the description of a new cassiduloid family and the evolution of some morphological features, are discussed. Cassiduloids (as defined here) most probably originated in the Early Cretaceous, and their evolutionary history has been dominated by high levels of homoplasy and a dearth of unique, novel traits. Despite their high diversity during the Palaeogene, there are only seven extant cassiduloid species, and three of these are relicts of lineages dating back to the Eocene. Future studies of the biology of these poorly known species, some of which brood their young, will yield further insights into the evolutionary history of this group. [ABSTRACT FROM AUTHOR]

Widely distributed species such as Arbacia stellata adjust patterns of their life history according to local conditions. In the present study the reproductive cycle of this species was analysed throughout a sampling year. Gonadal development cycle, sex ratio, actual fecundity and oocyte size distribution were characterized and the relationship of these reproductive characteristics with environmental variables such as sea surface temperature, photoperiod, chlorophyll a and net primary production evaluated. Our results showed that A. stellata is a gonochoric sea urchin. Gametogenesis was classified into six stages for both sexes (immature, growth, pre-maturity I, pre-maturity II, mature and spawning) and no synchrony was observed for the gonads between individuals. The female to male ratio was close to 1:1 in most months. The gonadosomatic index (GSI) showed significant differences between sexes or months; however, the highest values were observed during spring, with positive correlation with chlorophyll a. No significant differences were observed in the maturity index (MI) between sexes, with a positive correlation with temperature but negative with chlorophyll. Actual fecundity showed wide variations throughout the year and correlation with chlorophyll a and temperature. Oocyte size distribution was unimodal and the predominant frequency was that of mature oocytes. The reproductive cycle of A. stellata has a semi-continuous pattern for both sexes and partial spawning throughout the year in the sampling site. We observed nutrient assimilation in the gonads during spring and a larger reproductive activity from late summer to early winter. [ABSTRACT FROM AUTHOR]

A new quasimetric approach is used to statistically analyze taphonomic data from a commonly occurring shallow water clypeasteroid echinoid in order to obtain metric equivalent measurements of taphonomic alteration on an interval-like scale. This technique takes the character condition as well as its proportion into account and translates the taphonomic alteration into data, which behave as interval scaled and thus allows for the use of parametric as well as non-parametric statistics. Tests of Echinocyamus pusillus from Giglio Island (Mediterranean Sea, Italy) were analyzed with respect to a suite of taphonomic features including abrasion of the test surface, tubercles, ambulacral and genital pore margins as well as, if present, the outline and cross section of predatory drillholes. The degree of fragmentation and encrustation was also determined. Taphonomic features were analyzed using a semi-quantitative approach with three degrees of test alteration including non-altered, moderately altered, and highly altered which were statistically analyzed using non-parametric statistics due to highly non-normal distributed data. Abrasion intensities vary among different surface characters, with exposed areas of the test showing higher abrasion intensities than sheltered areas. Fragmentation occurs in low frequencies (7%) and fractures in the tests are almost absent (1.7%). Encrustation rates by bryozoans and serpulids can cover up to 80% of the test surface, but vary strongly among individuals and sample sites. Encrustation is independent of test size and prolongs overall test survival by crossing plate boundaries. The presence of drillholes in decreasing test preservation potentials is discussed with respect to analytical parameters.

Abstract The ability of chemical recognition is important for marine invertebrates to detect if host conditions (such as stress) are suitable for colonisation, and the presence of conspecifics can also be important for host switching. We investigated whether Dissodactylus crinitichelis can recognize the sand dollar Encope emarginata by chemical cues, and if factors such as host stress condition and presence of conspecifics may affect its chemical attraction to the host. In the host cue treatment, crabs showed no significant attraction (p =.1), although they perceived host stress conditions extensively in the host stress experiment, and mostly avoided the host (p <.01) water. In the host plus conspecifics experiment, crabs significantly responded (p <.01) to these cues. The lack of attraction to host cues suggested that the host presence is not enough to induce attraction on the crabs. Moreover, host cues might not be as stimulant as host stress cues, which might signal that hosts are not suitable, or that these cues might infer predation risk to the symbionts. Finally, the presence of conspecifics on the hosts may be a reliable way to encounter suitable hosts. It may also increase the chance of finding mating partners and thus mating opportunities; therefore, the higher preference for occupied hosts is important for the mating system of the crabs. The results reject the hypothesis that the symbiont-host relationship is based exclusively on host chemical cues, suggesting that intrinsic triggers, such as host condition and conspecific presence can induce host recognition and influence crab behaviour and mating success. Highlights • Symbiotic relationships in marine crustaceans may not be dependent on host chemical cues alone. • Symbionts can detect stress condition of the host as a mean to find suitable hosts and avoid predation risk. • Host stress cues are potentially repellent for symbionts. • The presence of potential mating partners is a trigger that motivate symbionts to locate hosts, more than host cues alone. [ABSTRACT FROM AUTHOR]

The two modes of development in sea urchins are direct development, in which the adult develops directly from the gastrula to the adult and does not feed, and indirect development, in which the adult develops indirectly through a feeding larva. In this account of the indirect, feeding larva of Heliocidaris tuberculata, the question raised is whether an evolutionary difference of unequal cell divisions contributes to the development of feeding structures in the indirect larva. In indirect development, the cell divisions at the fourth and fifth cell cycles of the zygote are unequal, with four small micromeres formed at the vegetal pole at the fifth cell division. In direct development, these cell divisions are not unequal. From their position at the head of the archenteron, the small micromeres are strategically located to contribute to the feeding tissues of the larva and the adult of H. tuberculata. [ABSTRACT FROM AUTHOR]

Aim: Species distribution modelling (SDM) represents a valuable alternative to predict species distribution over vast and remote areas of the ocean. We tested whether reliable SDMs can be generated for benthic marine organisms at the scale of the Southern Ocean. We aimed at identifying the main large‐scale factors that determine the distribution of the selected species. The robustness of SDMs was tested with regards to sampling effort, species niche width and biogeography. Location: Southern Ocean. Methods: The impact of sampling effort was tested using two sets of data: one set with all presence‐only data available until 2005, and a second set using all data available until 2015 including recent records from campaigns carried out during the Census of Antarctic Marine Life (CAML) and the International Polar Year (IPY) period (2005–2010). The accuracy of SDMs was tested using a ground‐truthing approach by comparing recent presence/absence data collected during the CAML and IPY period to pre‐CAML model predictions. Results: Our results show the significance of the SDM approach and the role of abiotic factors as important drivers of species distribution at broad spatial scale. The addition of recent data to the models significantly improved the prediction of SDM and changed the respective contributions of environmental predictors. However, the intensity of change varied between models depending on sampling tools, species ecological niche width and biogeographic barriers to dispersal. Main conclusions: We highlight the need for new data and the significance of the ground‐truthing approach to test the accuracy of SDMs. We show the importance of data collected through international initiatives, such as the CAML and IPY to the improvement of species distribution modelling at broad spatial scales. Finally, we discussed the relevance of SDM as a relevant marine conservation tool particularly in the context of climate change and the definition of Marine Protected Areas. [ABSTRACT FROM AUTHOR]

Background: Echinoidea is a clade of marine animals including sea urchins, heart urchins, sand dollars and sea biscuits. Found in benthic habitats across all latitudes, echinoids are key components of marine communities such as coral reefs and kelp forests. A little over 1000 species inhabit the oceans today, a diversity that traces its roots back at least to the Permian. Although much effort has been devoted to elucidating the echinoid tree of life using a variety of morphological data, molecular attempts have relied on only a handful of genes. Both of these approaches have had limited success at resolving the deepest nodes of the tree, and their disagreement over the positions of a number of clades remains unresolved. Results: We performed de novo sequencing and assembly of 17 transcriptomes to complement available genomic resources of sea urchins and produce the first phylogenomic analysis of the clade. Multiple methods of probabilistic inference recovered identical topologies, with virtually all nodes showing maximum support. In contrast, the coalescent-based method ASTRAL-II resolved one node differently, a result apparently driven by gene tree error induced by evolutionary rate heterogeneity. Regardless of the method employed, our phylogenetic structure deviates from the currently accepted classification of echinoids, with neither Acroechinoidea (all euechinoids except echinothurioids), nor Clypeasteroida (sand dollars and sea biscuits) being monophyletic as currently defined. We show that phylogenetic signal for novel resolutions of these lineages is strong and distributed throughout the genome, and fail to recover systematic biases as drivers of our results. Conclusions: Our investigation substantially augments the molecular resources available for sea urchins, providing the first transcriptomes for many of its main lineages. Using this expanded genomic dataset, we resolve the position of several clades in agreement with early molecular analyses but in disagreement with morphological data. Our efforts settle multiple phylogenetic uncertainties, including the position of the enigmatic deep-sea echinothurioids and the identity of the sister clade to sand dollars. We offer a detailed assessment of evolutionary scenarios that could reconcile our findings with morphological evidence, opening up new lines of research into the development and evolutionary history of this ancient clade. [ABSTRACT FROM AUTHOR]

Abstract The Entoprocta fauna still remains almost unexplored: many geographical areas have not yet been studied for their diversity, and almost nothing is known about deep-sea species. We described four new species of solitary Entoprocta from the family Loxosomatidae. The material was collected within a depth range between 3206 m and 3580 m during the German-Russian deep-sea expedition SokhoBio aboard R/V Akademik Lavrentyev in July - August 2015 in the Kuril Basin of the Sea of Okhotsk, Bussol Strait, and the adjacent open Pacific abyssal area. We used methods of light and scanning electronic microscopy and also laser confocal microscopy for morphological studies. Maximum likelihood and Bayesian analyses of partial DNA sequences of 18S and 28S rRNA genes were used to reconstruct phylogenetic trees. Loxosomella aeropsis sp. nov. was found on spines of the sea urchin Aeropsis fulva ; Loxosomella cyatiformis sp. nov. was found on shells of the propeamussiid bivalve Catillopecten squamiformis ; Loxosomella malakhovi sp. nov. was found living as an epibiont of the nephtyid polychaete Aglaophamus sp., and Loxosomella sextentaculata sp. nov., as an epibiont of the spionid polychaete Laonice sp. Echinoidea and Bivalvia have been first recorded as hosts of loxosomatid entoprocts in their symbiotic associations. A molecular phylogenetic analysis of partial 18S rRNA and 28S rRNA of Loxosomella aeropsis sp. nov., L. cyatiformis sp. nov., and L. malakhovi sp. nov. show that these species nest in the clade of solitary entoprocts among other Loxosomella species. Musculature of investigated species, Loxosomella aeropsis sp. nov and L. malakhovi sp. nov., is typical for loxosomatids and includes the longitudinal muscles of a stalk, the musculature of the digestive tract, the atrial muscular ring, and tentacle muscles. Each species has species-specific muscles so details of myoanatomy can be used for identification of species in addition to other morphological features. [ABSTRACT FROM AUTHOR]

Many sea urchins can detect light on their body surface and some species are reported to possess image-resolving vision. Here, we measure the spatial resolution of vision in the long-spined sea urchin Diadema africanum, using two different visual responses: a taxis towards dark objects and an alarm response of spine-pointing towards looming stimuli. For the taxis response we used visual stimuli, which were isoluminant to the background, to discriminate spatial vision from phototaxis. Individual animals were placed in the centre of a cylindrical arena under bright down-welling light, with stimuli of varying angular width placed on the arena wall at alternating directions from the centre. We tracked the direction of movement of individual animals in relation to the stimuli to determine whether the animals oriented towards the stimulus. We found that D. africanum responds by taxis towards isoluminant stimuli with a spatial resolution in the range of 29-69 deg. This corresponds to a theoretical acceptance angle of 38-89 deg, assuming a contrast threshold of 10%. The visual acuity of the alarm response of D. africanum was tested by exposing animals to different sized dark looming and appearing stimuli on a monitor.We found that D. africanum displays a spine-pointing response to appearing black circles of 13-25 deg angular width, corresponding to an acceptance angle of 60-116 deg, assuming the same contrast threshold as above. [ABSTRACT FROM AUTHOR]

Sea urchins play a crucial role in the health and dynamics of reef ecosystems. Diadema mexicanum is a dominant grazer and erosive agent of the substratum in reef environments in the eastern tropical Pacific. Its reported distribution extends from the middle of the Gulf of California (26° N) to northern Peru (6°23′ S), including oceanic islands. Here, we report the occurrence of Diadema mexicanum in Isla San Jorge (31°0′38.53″ N, 113°14′34.84″ W), the northernmost island in the Gulf of California, which extends its range an additional 600 km northward. Sea urchins, ranging in test size from 4.5 to 12.4 cm, were present at 2-6 m in October 2015. This test size was one of the largest reported for this species in the eastern tropical Pacific. Spine length in sea urchins in the upper gulf ranged from 3.3 to 15.6 cm. Variation in body size of sea urchin may reflect variation in more structurally complex reefs from isolated islands that provide shelter from predation. The reef structure of Isla San Jorge is formed by high coral cover of the scleractinian coral Porites panamensis, with an average colony height of 26.27 cm (standard error, SE ±1.58, n = 60), similar to coral reef communities of the southern Gulf of California. Although D. mexicanum is considered a great force of erosion to the substratum in reef environments in the eastern tropical Pacific, no evidence of erosion was observed at Isla San Jorge, indicating a balanced dynamic between herbivores, macroalgae, and corals. [ABSTRACT FROM AUTHOR]

The unique find of a stem group echinoid with a rotular, flexible corona composed of multiserial ambulacra and interambulacra from the Upper Muschelkalk Calcaire à Entroques (Middle Triassic, late Anisian, late Illyrian) of East France is described. The articulate specimen allows description of all characters besides the apical disc that was lost. The echinoid described as Lazarechinus mirabeti represents a new species and genus of the Carboniferous through Late Permian stem group echinoid family Proterocidaridae. Between the latest Permian proterocidarid Pronechinus and the new Lazarechinus is a gap of approx. 16 Ma covering the Early and early Middle Triassic. This makes the new genus a typical Lazarus taxon belonging to a lineage that disappeared during times of crisis and awoke in times of biotic recovery. Additional references of stem group echinoids are known from the middle Anisian of Southwest China and from the Carnian of Italy and Central China. The new finds provide evidence that the current concepts of echinoid evolution around the Permian-Triassic boundary require thorough reappraisal. The fortunate discovery of Lazarechinus in a Muschelkalk conservation Lagerstätte also encourages the systematic search of isolated sclerites assignable to stem group echinoids in Triassic sediments to provide more information on abundance, distribution, and habitats. [ABSTRACT FROM AUTHOR]

The Mg/Ca and Sr/Ca ratios in echinoderm skeletal calcite are used as a proxy for Phanerozoic seawater changes, since the skeletal concentrations are, to some extent, controlled by environmental factors. However, it remains unclear how the influence of environmental factors is modified by vital effects, especially in polar waters. Therefore, the goal of this study was to compare the ratios of Mg/Ca and Sr/Ca among the skeletal parts of 10 common Arctic echinoderm species belonging to three classes Echinoidea, Asteroidea and Ophiuroidea that contribute substantially to the carbon cycle in the Arctic benthic system. Significant differences were recorded in echinoid skeletal element concentrations among specific skeletal parts. The lowest Mg/Ca and Sr/Ca ratios were detected in the spines (mean Mg/Ca 37.5 ± 8.8 SD; Sr/Ca 1.8 ± 0.1). The components of the Aristotle's lantern (epiphyses, pyramids and rotulas) were characterised by the highest Mg levels (Mg/Ca 79.9 ± 6.0; 75.2 ± 9.1; 60.1 ± 3.8, respectively). It is likely that mouth parts experience greater mechanical pressure compared to other body parts, and the higher content of Mg in the Aristotle's lantern contributes to its robustness. We did not find any distinctive trends in the distribution of skeletal elements in the asteroid and ophiuroid skeletal parts. The heterogeneous concentrations of Mg and Sr in different skeleton parts of the echinoids suggest possible physiological regulation of the chemical composition rather than the composition only being influenced by the environment. We cannot recommend echinoderm skeletons as reliable indicators in palaeoenvironmental reconstructions due to the possible biological control of skeletal chemistry, which may interfere with the effect of environmental variables. [ABSTRACT FROM AUTHOR]

Sea urchins is the member of Echinoidea. This species can be found in tropical ma- rine water to the poles. The study aimed to know the types, the abundance and spread of sea urchins in Bengkayang Regency. The research, used the transect meth- od. Each station consisted of 3 transects with a length of 50 meters from the shore into the sea with the distance of 10 meters among the transects. This research ob- tained five species consisting of three species of the Diadema (genus) and two species of the Echinotrix (genus) i.e. Diadema antillarium, D. savignyi, D. setosum, Echinotrix calamaris and E. deadema. The density of sea urchins in Lemukutan Island ranges from 273 - 453 ind/Ha. The Density of sea urchins on Penata Kecil island ranges from 167 - 347 ind / Ha and on Penata Besar Island has a range from 307 - 387 ind/Ha. The highest diversity of sea urchins was found in Penata Kecil Island of (1.2355). The distribution of sea urchins in Lemukutan and Penata Besar Island was categorized into clumped and evenly distributed, while the distribution of sea urchin on Penata Kecil Island is included in the clustered and random categories. Distribution of sea urchins on the island is influenced by several factors such as sea water waves and food contained in the environment. [ABSTRACT FROM AUTHOR]

Se da la segunda cita de Leptosalenia barredai Forner, 2014. El equínido, de la familia Saleniidae L. Agassiz 1838, se ha encontrado en el cabo de Ajo (Cantabria), procedente de una unidad de calizas y margocalizas marinas someras con corales del Albiense inferior de la cuenca Vasco-Cantábrica. La especie sólo se conocía en su localidad tipo de Traiguera (cuenca del Maestrat), procedente de las capas de arenisca estuarinas del Albiense inferior y medio. Asimismo se establecen las diferencias entre L. barredai y L. faringdonensis Smith - Wright, 1990. Paralelamente se ofrece también una nueva cita del coral Actinoseris sp., (Cnidaria) del Albiense de Traiguera descrito con nomenclatura abierta por Reig (1993).

The health status of marine ecosystems can be fundamentally determined by the abundance and diversity of marine echinoderms. Philippines as part of the Indo-Pacific region is very rich and diverse in echinoderm species. In this study, the echinoderms of the intertidal zone of Goso-on and Vinapor, Carmen, Agusan del Norte were collected and identified. A total of 18 species were identified; five sea stars (Asteroidea), six sea urchins (Echinoidea), and seven sea cucumbers (Holothuroidea). Protoreaster nodosus, Linckia laevigata, and Diadema setosum were found to be abundant based on visual observation. The asteroids and echinoids collected were not yet assessed by the IUCN while the seven sea cucumbers were either least concern or data deficient. It is good to note that Holothuria scabra, an endangered sea cucumber was present in one sampling site. The low diversity, compared to some related studies, might suggest that exploitation is predominant particularly for sea cucumbers, considered a local delicacy. It is recommended that further studies must be conducted to evaluate the population of Holothuria scabra and other marine organisms to further evaluate the health of this marine ecosystem. Efforts must also be increased to further protect and conserve the marine faunal diversity of the study area. [ABSTRACT FROM AUTHOR]

Specimens of Syndesmis aethopharynx Westervelt & Kozloff, 1990 (Umagillidae, Rhabdocoela, Platyhelminthes) were collected from the intestine of several specimens of the sea urchin Paracentrotus lividus (Lamarck, 1816) [2] , Hansson, 2001 at the Greek coast. This represents the first report of a species of Syndesmis from Greece. Our study has revealed several previously-unreported morphological details and intraspecific variation, which are added to the species description. The position of S. aethopharynx within Umagillidae is confirmed for the first time through molecular data (based on nuclear 18S rDNA), using both Bayesian and maximum likelihood analyses. [ABSTRACT FROM AUTHOR]

The coastal strip of the Mexican Pacific and Gulf of California includes 11 states, and considering Isla Guadalupe and the Revillagigedo archipelago, Mexico has 2 364 200 km2 of marine extension in the Pacific Ocean. Studies of deep benthic macroinvertebrates for this area began with the Albatross, which traveled from the Guadalupe Islands to Guaymas in 1891. To date, 26 species of echinoids have been reported, with a bathymetric range that exceeds 200 m. In the present work, the previous bibliographic records for echinoids that were collected within the limits of the Mexican Pacific were corroborated. The taxonomic identity of the 26 species reported was also corroborated by 11 689 specimens deposited in four scientific collections: two Mexican collections (3 322 specimens in the National Collection of Echinoderms "Dra. M. E. Caso" of the ICML, UNAM and 6 673 specimens deposited in the Invertebrate Reference Collection of the Mazatlán Station - ICML, UNAM) and two international collections (1 420 specimens deposited at the National Museum of Natural History, Smithsonian Institution, Washington, DC, and 140 specimens deposited at the Museum of Comparative Zoology, Harvard University). No collection records were found at depths greater than 200 m for the species Lytechinus pictus (Verrill, 1867), Clypeaster europacificus H.L. Clark, 1914, Dendraster excentricus (Eschscholtz, 1831), Lovenia cordiformis A. Agassiz, 1872 and Brissus obesus Verrill, 1867. No records were found for Kamptosoma asterias (A. Agassiz, 1881), Araeolampas fulva (A. Agassiz, 1879) and Nacospatangus depressus H.L. Clark, 1917, which belonged to specimens collected within the limits of the Mexican Pacific. Within the material examined in the scientific collections specimen records were found only for 18 of the 26 species of sea urchins that were collected at a depths greater than 200 m in the Mexican Pacific. No bibliographic record or specimens were found to validate geographic or bathymetric distribution for eight species. [ABSTRACT FROM AUTHOR]

The Asian seaweed Undaria pinnatifida invaded Argentina in 1992 (Golfo Nuevo, Patagonia). Its range has expanded and it has changed the native benthic community. Sea urchins are usually generalist herbivores that have a key role in controlling seaweeds. Arbacia dufresnii is the most abundant sea urchin in the coastal areas of northern Patagonia. The aim of this study was to relate the population parameters of A. dufresnii to the presence of the invasive seaweed. In 2012 we sampled sites with different invasion stages (advanced: Golfo Nuevo, recently invaded: San José Gulf, Punta Tehuelche; no invasion: San José Gulf, Zona 39). Sea urchin density was higher in the invaded sites and varied with the seaweed cycle. In addition, there were variations in the size distribution in the invaded sites. The invasive algae probably affects urchin populations because it is a new source of food that changes environmental structure (it provides microhabitat for new recruits) and affects the native benthic community. [ABSTRACT FROM AUTHOR]