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This research explores the significance of rapid burial in preserving fossils, with a particular focus on free-living echinoderms. Experiments were based on ophiuroids to simulate burial under different turbiditic flows. The results showed that a bed thickness of around 10 cm is a limit for the preservation of whole skeletons in most cases. The type of sediment can affect the integrity of the buried skeletons, with sand deposition resulting in higher rates of autotomy. However, mud deposition did not show any numbing effect, as previously believed for echinoderms. In contrast, freshwater-rich sediments can play a critical role, paralysing specimens and preventing escape postures through rapid changes in salinity. From this, the study highlights the importance of extrabasinal turbidites, generated outside the marine basin, in the fossilization of marine invertebrates. Such sediments are rich in fresh water and can be more efficient burial traps compared to other intrabasinal deposits generated by storm waves or submarine landslides. [ABSTRACT FROM AUTHOR]

Echinoderm skeletons are composed of calcium carbonate ossicles that join in a variety of ways to form flexible or, more rarely, fixed joints. Ossicle "fusion" in echinoderms has been widely reported in the literature to form various types of fixed joint, but fusion in the sense of chemical union (ankylosis) of the calcitic ossicles has rarely been demonstrated. The arm skeleton of ophiuroids is primarily composed of a series of vertebral ossicles; each vertebra is a compound ossicle that consists of paired ambulacral ossicles united by a fixed joint, often reported to be fused. Development of vertebral ossicles in the amphiurid brittlestar Ophiophragmus filograneus from the arm tip to the oral frame was examined using scanning electron microscopy to follow ontogeny of the vertebra. As an ambulacral ossicle grew, its stereomal trabeculae interdigitated and interlocked by hooking around those of its paired ambulacral, forming the characteristic sinuous suture line central to ophiuroid vertebrae. This three‐dimensional interlocking of stereom formed the joint between paired ambulacrals. With further growth of the vertebra, limited fusion of trabeculae of the paired ambulacrals added to the structure of the joint, primarily at the articular surfaces between successive vertebrae. The joint found here with interlocked trabeculae between ambulacral ossicles of O. filograneus appears to be the same type described in the literature in some echinoids and other ophiuroids. This unique type of fixed joint is described here and named the "campylogomphosis" (Greek: campylos, bent; gomphos, bolt). This newly recognized joint might have implications in echinoderm phylogeny, comparative biology, medicine, and materials science. [ABSTRACT FROM AUTHOR]

The Cambrian and Ordovician radiations marked the origins of all major echinoderm clades and established their Phanerozoic ecological blueprint. Recent claims of modest innovation of early echinoderms and other animals suggest constraints on novelty during the origins of phyla. Here, we document the life‐habit richness, body size, tiering, habitat usage, mobility, diet and foraging habits of 366 Cambrian–Ordovician echinoderm genera across a time‐scaled phylogeny to identify the timing and impact of novelty. Most early echinoderms were sedentary, filter‐feeding microbivores, and their body sizes, diets and modes of locomotion were largely unchanged through time, despite major volatility in taxonomic composition. Cambrian echinoderms lived close to the seafloor, with stylophorans first evolving semi‐infaunality. Many Ordovician echinoderms lived farther from the seafloor, with more complex filter‐feeding organs and tiering structure, often using other organisms as substrates. Mobile carnivores and mass‐feeders emerge then, too, across diverse asterozoans and echinozoans. Most of these novelties coincide with the origins of individual clades during the early and late Cambrian (Terreneuvian/Series 2 and Furongian), and 10–20 million years pass before most become ecologically important. Life‐habit evolution within most taxa involved new variations in these traits, with crinoids and asterozoans better able to shift strategies. The Ordovician radiation records more new variability in pre‐existing Cambrian life habits rather than radical re‐invention, with important novelties (like mobile carnivory and mass‐feeding, increased height off the seafloor, and biotic substrates) becoming ecologically more impactful. Taxa with these strategies were those best able to capitalize on the newly heterogeneous Ordovician world. [ABSTRACT FROM AUTHOR]

Microbes play a critical role in the development and health of marine invertebrates, though microbial dynamics across life stages and host generations remain poorly understood in most reef species, especially in the context of climate change. Here, we use a 4‐year multigenerational experiment to explore microbe–host interactions under the Intergovernmental Panel on Climate Change (IPCC)‐forecast climate scenarios in the rock‐boring tropical urchin Echinometra sp. A. Adult urchins (F0) were exposed for 18 months to increased temperature and pCO2 levels predicted for years 2050 and 2100 under RCP 8.5, a period which encompassed spawning. After rearing F1 offspring for a further 2 years, spawning was induced, and F2 larvae were raised under current day and 2100 conditions. Cross‐generational climate effects were also explored in the microbiome of F1 offspring through a transplant experiment. Using 16S rRNA gene sequence analysis, we determined that each life stage and generation was associated with a distinct microbiome, with higher microbial diversity observed in juveniles compared to larval stages. Although life‐stage specificity was conserved under climate conditions projected for 2050 and 2100, we observed changes in the urchin microbial community structure within life stages. Furthermore, we detected a climate‐mediated parental effect when juveniles were transplanted among climate treatments, with the parental climate treatment influencing the offspring microbiome. Our findings reveal a potential for cross‐generational impacts of climate change on the microbiome of a tropical invertebrate species. [ABSTRACT FROM AUTHOR]

Spatangoid echinoids belonging to Heteraster found in the Lower Cretaceous limestones and calcareous deposits of the Tirgan and Sarcheshmeh formations (Barremian–Aptian) in the Bahman jan‐Bala stratigraphic section on the northern flank of the Borouj syncline, situated in the eastern Kopet‐Dagh Basin, northeastern Iran are assessed as a sexually dimorphic species. Sexual dimorphism is a common feature in echinoids and, in this study of Heteraster renngarteni Poretzkaja, 1961, sexual dimorphism has been detected for the first time in the family Toxasteridae. [ABSTRACT FROM AUTHOR]

Rising ocean temperatures are threatening marine species and populations worldwide, and ectothermic taxa are particularly vulnerable. Echinoderms are an ecologically important phylum of marine ectotherms and shifts in their population dynamics can have profound impacts on the marine environment. The effects of warming on echinoderms are highly variable across controlled laboratory‐based studies. Accordingly, synthesis of these studies will facilitate the better understanding of broad patterns in responses of echinoderms to ocean warming. Herein, a meta‐analysis incorporating the results of 85 studies (710 individual responses) is presented, exploring the effects of warming on various performance predictors. The mean responses of echinoderms to all magnitudes of warming were compared across multiple biological responses, ontogenetic life stages, taxonomic classes, and regions, facilitated by multivariate linear mixed effects models. Further models were conducted, which only incorporated responses to warming greater than the projected end‐of‐century mean annual temperatures at the collection sites. This meta‐analysis provides evidence that ocean warming will generally accelerate metabolic rate (+32%) and reduce survival (−35%) in echinoderms, and echinoderms from subtropical (−9%) and tropical (−8%) regions will be the most vulnerable. The relatively high vulnerability of echinoderm larvae to warming (−20%) indicates that this life stage may be a significant developmental bottleneck in the near‐future, likely reducing successful recruitment into populations. Furthermore, asteroids appear to be the class of echinoderms that are most negatively affected by elevated temperature (−30%). When considering only responses to magnitudes of warming representative of end‐of‐century climate change projections, the negative impacts on asteroids, tropical species and juveniles were exacerbated (−51%, −34% and −40% respectively). The results of these analyses enable better predictions of how keystone and invasive echinoderm species may perform in a warmer ocean, and the possible consequences for populations, communities and ecosystems. [ABSTRACT FROM AUTHOR]

The Lover Devonian Hunsrück Slate in western Germany is world‐famous for its exceptionally preserved and beautiful fossils. What makes this Konservat‐Lagerstätte so fascinating is its unique style of pyritization that has perfectly captured an entire ecosystem, from delicate echinoderms with preserved soft tissues to the Lovecraftian Mimetaster. [ABSTRACT FROM AUTHOR]

Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and humans, among a wide variety of ecologically and morphologically disparate taxa. However, their early evolution is poorly understood, due in part to their disparity, which makes identifying commonalities difficult, as well as their relatively poor early fossil record. Here, we review the available morphological, palaeontological, developmental, and molecular data to establish a framework for exploring the origins of this important and enigmatic group. Recent fossil discoveries strongly support a vermiform ancestor to the group Hemichordata, and a fusiform active swimmer as ancestor to Chordata. The diverse and anatomically bewildering variety of forms among the early echinoderms show evidence of both bilateral and radial symmetry. We consider four characteristics most critical for understanding the form and function of the last common ancestor to Deuterostomia: Hox gene expression patterns, larval morphology, the capacity for biomineralization, and the morphology of the pharyngeal region. We posit a deuterostome last common ancestor with a similar antero‐posterior gene regulatory system to that found in modern acorn worms and cephalochordates, a simple planktonic larval form, which was later elaborated in the ambulacrarian lineage, the ability to secrete calcium minerals in a limited fashion, and a pharyngeal respiratory region composed of simple pores. This animal was likely to be motile in adult form, as opposed to the sessile origins that have been historically suggested. Recent debates regarding deuterostome monophyly as well as the wide array of deuterostome‐affiliated problematica further suggest the possibility that those features were not only present in the last common ancestor of Deuterostomia, but potentially in the ur‐bilaterian. The morphology and development of the early deuterostomes, therefore, underpin some of the most significant questions in the study of metazoan evolution. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of the study aims to understand the regeneration process and its cytology mechanism in economic echinoderms. Materials and Methods: The intestine regeneration process of Apostichopus japonicus was investigated by immunohistochemistry and the cell proliferation was detected by immunofluorescence and flow cytometry. Fibroblast growth factor 4 of A. japonicus (AjFGF4) was screened by RNA‐seq analysis and validated to regulate cell proliferation by siAjFGF4 and recombinant‐AjFGF4 treatment. The binding and co‐localization of AjFGF4 and AjFGFR2 were verified by Co‐IP, GST‐pull down, and immunofluorescence. Then, the AjFGF4‐AjFGFR2‐ERK‐cell cycle axis was examined by western blot, immunofluorescence, and flow cytometry techniques. Results: The mesentery was served as the epicenter of intestinal regeneration via activating cell proliferation and other cellular events. Mechanically, AjFGF4‐mediated cell proliferation was dependent on the binding to its receptor AjFGFR2, and then triggered the conserved ERK–MAPK pathway but not JNK and p38 pathway. The activated ERK–MAPK subsequently mediated the expression of cell cycle regulatory proteins of CDK2, Cyclin A, and Cyclin B to promote cell proliferation. Conclusions: We provide the first functional evidence that AjFGF4‐AjFGFR2‐ERK‐cell cycle axis mediated cell proliferation was the engine for mesentery‐derived intestine regeneration in echinoderms. [ABSTRACT FROM AUTHOR]

Global warming is affecting the Antarctic continent in complex ways. Because Antarctic organisms are specialized to living in the cold, they are vulnerable to increasing temperatures, although quantitative analyses of this issue are currently lacking. Here we compiled a total of 184 estimates of heat tolerance belonging to 39 marine species and quantified how survival is affected concomitantly by the intensity and duration of thermal stress. Species exhibit thermal limits displaced toward colder temperatures, with contrasting strategies between arthropods and fish that exhibit low tolerance to acute heat challenges, and brachiopods, echinoderms, and molluscs that tend to be more sensitive to chronic exposure. These differences might be associated with mobility. A dynamic mortality model suggests that Antarctic organisms already encounter temperatures that might be physiologically stressful and indicate that these ecological communities are indeed vulnerable to ongoing rising temperatures. [ABSTRACT FROM AUTHOR]

Ophiuroidea is the most speciose of all classes of Echinoderma. It is an important component in benthic ecosystems, occurring in almost all ecological niches of modern seas. To date, the phylogeny and complete evolutionary history of the ophiuroids have not yet been fully resolved. In this study, we sequenced the complete mitochondrial genomes (mitogenomes) of Ophiothrix (Ophiothrix) exigua and two deep‐sea species Histampica sp. CS049 and Ophioplinthaca sp. M5261. These two deep‐sea ophiuroids displayed reversed strand‐compositional bias and rearranged gene orders. Thirteen distinct patterns of mitochondrial gene order among ophiuroid mitogenomes were detected, with two gene order newly found in Ophiuroidea. Our data supported the gene order found in all sampled Ophiuridae as the most likely ancestral order of all Ophiuroidea. To improve phylogenetic accuracy based on nucleotide differences, two different criteria were used for the analyses: (i) nucleotide sequence from all codon positions (PCG123); (ii) the NTE method ("Neutral Transitions Excluded") for ameliorating the misleading effects of a reverse strand bias in the data. The two methods confirmed the polyphyly of the orders Ophiacanthida and Amphilepidia. At family and genus level, Ophiuridae, Ophionotus and Ophioplinthus were not monophyletic. The most notable exception was that the NTE phylogeny showed low variation of branch length. NTE dataset generated younger age for most lower‐level nodes than that from PCG123 dataset. All analyses suggested that the ophiuroids radiation occurred around the Permian–Triassic mass extinction event, and the divergence time of the deep‐sea lineages was during the Cretaceous. [ABSTRACT FROM AUTHOR]

The article titled "Correction to 'Ecological novelty at the start of the Cambrian and Ordovician radiations of echinoderms'" in the journal Palaeontology provides a corrected version of Figure 6. The figure illustrates the echinoderm phyloecospace during the Cambrian and Ordovician periods using the time-scaled UEH phylogeny number 49 as an example. The figure also includes the ecospace for the EAT topology as an alternative representation. The figure shows the distribution of different taxonomic classes and highlights changes occurring prior to diversification during the Cambrian and Ordovician radiations. The article acknowledges the error and apologizes for it. [Extracted from the article]

Ophiuroidea are one of the most diverse classes among extant echinoderms, characterized by their flexible arms composed of a series of ossicles called vertebrae, articulating with each other proximally and distally. Their arms show a wide range of motion, important for feeding and locomotion, associated with their epizoic and non‐epizoic lifestyles. It remains to be explored to what degree the phenotypic variation in these ossicles also reflects adaptations to these lifestyles, rather than only their phylogenetic affinity. In this study, we analyzed the 3D shape variation of six arm vertebrae from the middle and distal parts of an arm in 12 species, belonging to the intertidal, subtidal and bathyal zones and showing epizoic and non‐epizoic behaviors. A PERMANOVA indicated a significant difference in ossicle morphology between species and between lifestyles. A principal component analysis showed that the morphology of epizoic ophiuroids is distinct from non‐epizoic ones; which may reflect variation in arm function related to these different lifestyles. The Phylogenetic MANOVA and phylogenetic signal analysis showed that shape variation in the vertebral articulation seems to reflect ecological and functional adaptations, whereas phylogeny controls more the lateral morphology of the vertebrae. This suggests a convergent evolution through ecological adaptation to some degree, indicating that some of these characters may have limited taxonomic value. [ABSTRACT FROM AUTHOR]

For marine ectotherms, larval success, planktonic larval duration and dispersal trajectories are strongly influenced by temperature, and therefore, ocean warming and heatwaves have profound impacts on these sensitive stages. Warming, through increased poleward flow in regions with western boundary currents, such as the East Australia Current (EAC), provides opportunities for range extension as propagules track preferred conditions. Two sea urchin species, Centrostephanus rodgersii and Heliocidaris tuberculata, sympatric in the EAC warming hotspot, exhibit contrasting responses to warming. Over half a century, C. rodgersii has undergone marked poleward range extension, but the range of H. tuberculata has not changed. We constructed thermal performance curves (TPC) to determine if contrasting developmental thermal tolerance can explain this difference. The temperatures tested encompassed present‐day distribution and forecast ocean warming/heatwave conditions. The broad and narrow thermal optimum (Topt) ranges for C. rodgersii and H. tuberculata larvae (7.2 and 4.7°C range, respectively) matched their realized (adult distribution) thermal niches. The cool and warm temperatures for 50% development to the feeding larva approximated temperatures at adult poleward range limits. Larval cool tolerances with respect to mean local temperature differed, 6.0 and 3.8°C respectively. Larval warm tolerances were similar for both species as are the adult warm range edges. The larvae of both species would be sensitive to heatwaves. Centrostephanus rodgersii has stayed in place and shifted in space, likely due to its broad cold–warm larval thermal tolerance and large thermal safety margins. Phenotypic plasticity of the planktonic stage of C. rodgersii facilitated its range extension. In contrast, larval cold intolerance of H. tuberculata explains its restricted range and will delay poleward extension as the region warms. In a warming ocean, we show that intrinsic thermal biology traits of the pelagic stage provide an integrative tool to explain species‐specific variation in range shift patterns. [ABSTRACT FROM AUTHOR]

Coelomocytes in the Holothuroidea are traditionally identified according to their morphology through light, fluorescence, or electron microscopy. Former studies have typically used only one method, with few works combining two or more approaches. Studies using cytocentrifugation to study these cells are scarcer. Thus, for the first time, an integrative approach was used to compare coelomocytes in Holothuroidea. This approach consisted of living and stained cells, scanning electron microscopy (for spherule cells), and accurate morphometric analyses. Specifically, we used specimens of Holothuria grisea, Holothuria arenicola, and Holothuria tubulosa to test whether cytocentrifugation could be valuable in comparative studies with coelomocytes, whether an integrative approach could help to understand spherule cell diversity, and whether closely related species, even those having distinct geographic distributions and ecological requirements, would have a similar population of coelomocytes. Our results showed seven distinct cell types in these species, including phagocytes, fusiform cells, morula cells, acidophilic spherulocytes, spherulocytes, progenitor cells, and crystal cells. Total and differential cell counts, along with morphometric parameters, were similar among species. Morphometric analyses of spherule cells revealed consistent differences among the diameter of their cytoplasmic spherules, as well as a set of different morphotypes in acidophilic spherulocytes and spherulocytes. Cytospin preparations proved to be quite useful because they provided constant morphological and morphometric data, allowing accurate identification of the cell types and comparisons among species. Moreover, this study highlighted (1) that the spherule diameter is a good parameter to separate spherule cells and (2) a putative maturation process to acidophilic spherulocytes and spherulocytes. Lastly, we showed that the cells of these species are very similar, regardless of their geographic distribution and ecology. Thus, our work contributes to a better understanding of the coelomocytes in Holothuria, a genus with a wide geographic distribution. The present study may be useful to establish these species as important model organisms, as well as bring insights into the functions of coelomocytes. [ABSTRACT FROM AUTHOR]

Echinoderms, including sea urchins and starfish, have played important roles in cell, developmental and evolutionary biology research for more than a century. However, since most of them take a long time to mature sexually and their breeding seasons are limited, it has been difficult to obtain subsequent generations in the laboratory, resulting in them not being recognized as model organisms in recent genetics research. To overcome this issue, we maintained and obtained gametes from several nonmodel sea urchins in Japan and finally identified Temnopleurus reevesii as a suitable model for sea urchin genetics. Genomic and transcriptomic information was obtained for this model, and the DNA database TrBase was made publicly available. In this review, we describe how we found this species useful for biological research and show an example of CRISPR/Cas9 based knockout sea urchin. [ABSTRACT FROM AUTHOR]

Chemosensation is a critical signalling process in animals and especially important in sea cucumbers, a group of ecologically and economically important marine echinoderms (class Holothuroidea), which lack audio and visual organs and rely on chemical sensing for survival, feeding and reproduction. The ionotropic receptors are a recently identified family of chemosensory receptors in insects and other protostomes, related to the ionotropic glutamate receptor family (iGluR), a large family of membrane receptors in metazoan. Here we characterize the echinoderm iGluR subunits and consider their possible role in chemical communication in sea cucumbers. Sequence similarity searches revealed that sea cucumbers have in general a higher number of iGluR subunits when compared to other echinoderms. Phylogenetic analysis and sequence comparisons revealed GluH as a specific iGluR subfamily present in all echinoderms. Homologues of the vertebrate GluA (aka α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid, AMPA), GluK (aka kainate) and GluD (aka delta) were also identified. The GluN (aka N‐methyl‐d‐aspartate, NMDA) as well as the invertebrate deuterostome subfamily GluF (aka phi) are absent in echinoderms. The echinoderm GluH subfamily shares conserved structural protein organization with vertebrate iGluRs and the ligand binding domain (LBD) is the most conserved region; genome analysis indicates evolution via lineage and species‐specific tandem gene duplications. GluH genes (named Grih) are the most highly expressed iGluRs subunit genes in tissues in the sea cucumber Holothuria arguinesis, with Griha1, Griha2 and Griha5 exclusively expressed in tentacles, making them candidates to have a chemosensory role in this species. The multiple GluH subunits may provide alternative receptor assembly combinations, thus expanding the functional possibilities and widening the range of compounds detected during aggregation and spawning in echinoderms. [ABSTRACT FROM AUTHOR]

The morphologies of the internal organs of echinoderm larvae and juveniles are difficult to study using conventional optical microscopes because of their structural complexity and opaqueness. This paper describes an easy and rapid protocol involving Nile blue staining followed by benzyl alcohol/benzyl benzoate (BABB) clearing to overcome this limitation. This method was developed for a three‐dimensional (3D) analysis of the internal structures of advanced larvae and juveniles of echinoderms (the sea lily Metacrinus rotundus, the sea urchin Hemicentrotus pulcherrimus, and the sand dollar Scaphechinus mirabilis) and is suitable for obtaining serial optical images by confocal microscopy without the use of specific antibodies or special reagents for labeling. Nile blue is an easy‐to‐use stain that offers several advantages for confocal microscopy such as it can stain various tissues with strong fluorescent signals without substantial bleaching during observation. We found that the strong fluorescence signal of Nile blue quickly yielded clear high‐resolution optical section images for 3D reconstruction. BABB clearing rendered opaque larvae highly transparent. The clearing procedure was also easy and quick. During the process, agarose embedding prior to staining and clearing was found to be critical for handling the samples of less than 500‐μm length and stabilizing their orientations. To conclude, the protocol described is useful for performing a rapid and accurate 3D morphological analysis of echinoderm larvae and juveniles. [ABSTRACT FROM AUTHOR]

Gastric mesenchymal tumors are relatively rare, and their molecular pathogeneses are poorly understood, except for gastrointestinal stromal tumor, desmoid, and inflammatory myofibroblastic tumors. We report a case of a gastric mesenchymal tumor with prominent smooth muscle cell differentiation and an echinoderm microtubule‐associated protein‐like 4‐anaplastic lymphoma kinase (EML4‐ALK) fusion. On gross section, the tumor was 26 mm at the largest diameter, well‐circumscribed, and located in the submucosal and muscular layers of the stomach wall. Histologically, the tumor comprised intersecting fascicles of spindle cells, non‐atypical nuclei, and highly eosinophilic cytoplasm. Myxoid changes were observed focally, but inflammatory infiltrates were only evident in limited areas. Immunochemical staining revealed that the tumor was positive for α‐smooth muscle actin and desmin. Diffuse positive staining for h‐caldesmon was observed throughout the tumor, which suggested smooth muscle cell differentiation. Intracytoplasmic staining for ALK protein was also observed, and fluorescence in situ hybridization using ALK break‐apart probes showed split chromosomal signals. RNA‐sequencing analysis identified EML4‐ALK fusion transcripts. We concluded that the tumor was a gastric mesenchymal tumor with smooth muscle differentiation based on its distinct differential smooth muscle properties, such as highly eosinophilic cytoplasm and diffuse expression of h‐caldesmon. Furthermore, activated ALK may underly the tumor's pathogenesis. [ABSTRACT FROM AUTHOR]

Framework‐building corals create the three‐dimensional structure of coral reefs and are subject to predation from fishes, echinoderms, and gastropods. Anthropogenic stressors can magnify the effects of such top‐down pressure on foundation species. The gastropod Coralliophilaviolacea (Kiener, 1836) depletes coral energy reserves via predation, potentially increasing coral susceptibility to land‐based pollution (i.e., sediment accumulation and nutrient pollution). We hypothesized that sedimentation would worsen coral mortality, while nutrient enrichment would mitigate the harmful effects of sediment and predation on coral mortality by increasing the densities of algal symbionts. To test these hypotheses, we conducted in situ surveys of the fringing reefs in Mo'orea, French Polynesia to explore the relationships among massive Poritesspp. cover, C. violacea densities, and sediment accumulation on coral colonies across low and high nutrient sites. We also conducted a factorial field experiment to test the interactions among these stressors on coral tissue mortality, symbiont densities, and chlorophyll. Massive Porites colonies at higher nutrient sites had C. violacea densities 13 times higher than at low nutrient sites but there was no difference in the amount of live tissue on coral colonies with or without snails among these sites. In our experiment, there were interactions between predation and nutrients as well as nutrients and sediment that impacted coral mortality. Sedimentation and predation by C. violacea increased coral tissue mortality independently by ~20%. Nutrient enrichment reduced this effect in corals under sedimentation or predation pressure by lowering coral tissue mortality by 18% and increasing algal symbiont densities by ~28%. Our results indicate that sediment does not magnify top‐down pressure on this coral, and that moderate nutrient enrichment may interact with predation in complex, unexpected ways to alter the responses of corals to top‐down pressure. [ABSTRACT FROM AUTHOR]

Despite descending from heavily calcified ancestors, the holothuroid skeleton is fully internal and composed of microscopic ossicles and a ring of plates bound by connective tissue, the calcareous ring. The calcareous ring exhibits a complex and poorly understood morphology; as a result, establishing unambiguous homology statements about its macrostructure has been challenging and phylogenetic studies have had to simplify this important structure. Here, we provide the first broad comparative study of Dendrochirotida calcareous rings using micro‐computed tomography (μCT). A detailed description of the three‐dimensional macrostructure of the calcareous ring of 10 sea cucumber species, including rare and type specimens, is presented. The structures observed were highly variable at the subfamily level, especially at the point of tissue attachment. The relationship between the calcareous ring and its associated organs, and their functional morphology are discussed. To aid future phylogenetic studies, we listed 22 characters and performed a preliminary cladistic analysis. The topology obtained supports the idea that the simple, cucumariid ring is ancestral to the mosaic‐like phyllophorid ring; however, it did not support the monophyly of the cucumariids. It also did not support the family Sclerodactylidae, which was described based on the ring morphology. Differently from the dermal ossicles, which are highly homoplastic, the general homoplasy index of the calcareous ring characters was relatively low. This result highlights the importance of this structure for phylogenetic inference. Unfortunately, time since collection, rough collection methods and fixation can damage the skeleton, and the calcareous ring is often overlooked in taxonomic descriptions. The data presented here will improve our understanding of holothuroid relationships and facilitate studies on holothuroid functional morphology and biomechanics. [ABSTRACT FROM AUTHOR]

Green sea urchins (Strongylocentrotus droebachiensis) are dominant components of benthic ecosystems that form aggregations and can transform entire kelp forests into barren systems. While these urchins are known to unwittingly consume practically anything in their path while grazing, detailed descriptions of active predatory behaviour on known predators (i.e., predator–prey reversal) are undocumented. Here, we use laboratory observations to describe the behavioural tactics used by starved S. droebachiesis to actively attack and consume sea stars, Crossaster papposus—a known predator of S. droebachiensis. We observed urchins preying on three separate sea stars, with one being substantially consumed by urchins within 24 hr. Urchins exhibited a direct mode of attack on sea stars by individually mounting and consuming the tips of the arms. Interestingly, we did not observe any conflict between individual urchins for attacking the sea star despite there being ≈80 starving urchins in the tank (and only 10–12 arms on the sea stars). Some sea stars did not attempt to escape urchin predation at all, while others attempted to escape by fleeing and lifting arms on top of the urchins. Given that sensory perception in sea stars is largely derived from the arm tips, we suggest that urchins directly attack and consume many sea star arm tips in an attempt to "pin" sea stars before consuming them. As such, we term this predatory behaviour "urchin pinning." These observations ultimately provide the first detailed behavioural documentation of how urchins actively prey on a known predator and provide a basis for a wealth of future research. [ABSTRACT FROM AUTHOR]

Aim: The role of biotic interactions in generating broad patterns in organismal phenotypes is a central question in macroecology. We investigate global patterns in feeding morphology among featherstars, a globally widespread group of suspension‐feeding echinoderms whose evolutionary history has been demonstrably shaped by predators. Location: World's oceans. Taxon: Crinoidea. Methods: We tested for global patterns in the featherstar suspension‐feeding apparatus, a filter made up of 5–200 arms which is the main interface with predators. We investigate a geospatial dataset of 23,950 occurrences in 442 species using statistical analyses including quantile regression and a new permutation‐based phylogenetic comparative approach appropriate for testing for a broad range of patterns in data with strange distributions. Results: We find that featherstars exhibit a latitudinal gradient in arm number: arm number is both greater on average and more variable between species at lower latitudes. This pattern holds across depths and hemispheres and is not a spurious result of either the latitudinal diversity gradient or phylogenetic autocorrelation. Tropical featherstars that conceal themselves have fewer arms, and also appear to experience less intense predation. Main conclusions: Temperature, primary productivity and substrate type do not adequately explain the latitudinal gradient in arm number. We attribute it instead to a corresponding gradient in predation intensity: many armed featherstars can withstand more intense arm loss to predators. Concealment and other alternate solutions to the problem of predation, along with reproductive costs associated with having many arms, explain why the trend is wedge‐shaped rather than linear. Our findings constitute a latitudinal gradient in functional diversity, paralleling recent findings in other taxa. The gradient may be a consequence of shallow tropical reefs; inasmuch as reefs as centres of biotic interactions promote functional richness, changes in the distribution of reefs through deep time probably entailed shifts in the global deployment of ecological diversity. [ABSTRACT FROM AUTHOR]

It has been argued that skeletal Mg/Ca ratio in echinoderms is mostly governed by Mg2+ and Ca2+ concentrations in the ambient seawater. Accordingly, well‐preserved fossil echinoderms were used to reconstruct Phanerozoic seawater Mg2+/Ca2+ ratio. However, Mg/Ca ratio in echinoderm skeleton can be affected by a number of environmental and physiological factors, the effects of which are still poorly understood. Notably, experimental data supporting the applicability of echinoderms in paleoenvironmental reconstructions remain limited. Here, we investigated the effect of ambient Mg2+/Ca2+ seawater ratio and diet on skeletal Mg/Ca ratio and growth rate in two echinoid species (Psammechinus miliaris and Prionocidaris baculosa). Sea urchins were tagged with manganese and then cultured in different Mg2+/Ca2+ conditions to simulate fluctuations in the Mg2+/Ca2+ seawater ratios in the Phanerozoic. Simultaneously, they were fed on a diet containing different amounts of magnesium. Our results show that the skeletal Mg/Ca ratio in both species varied not only between ossicle types but also between different types of stereom within a single ossicle. Importantly, the skeletal Mg/Ca ratio in both species decreased proportionally with decreasing seawater Mg2+/Ca2+ ratio. However, sea urchins feeding on Mg‐enriched diet produced a skeleton with a higher Mg/Ca ratio. We also found that although incubation in lower ambient Mg2+/Ca2+ ratio did not affect echinoid respiration rates, it led to a decrease or inhibition of their growth. Overall, these results demonstrate that although skeletal Mg/Ca ratios in echinoderms can be largely determined by seawater chemistry, the type of diet may also influence skeletal geochemistry, which imposes constraints on the application of fossil echinoderms as a reliable proxy. The accuracy of paleoseawater Mg2+/Ca2+ calculations is further limited by the fact that Mg partition coefficients vary significantly at different scales (between species, specimens feeding on different types of food, different ossicle types, and stereom types within a single ossicle). [ABSTRACT FROM AUTHOR]

Reconstructing the function and behaviour of extinct groups of echinoderms is problematic because there are no modern analogues for their aberrant body plans. Cinctans, an enigmatic group of Cambrian echinoderms, exemplify this problem: their asymmetrical body plan differentiates them from all living species. Here, we used computational fluid dynamics to analyse the functional performance of cinctans without assuming an extant comparative model. Three‐dimensional models of six species from across cinctan phylogeny were used in computer simulations of water flow. The results demonstrate that cinctans with strongly flattened bodies produced much less drag than species characterized by dorsal protuberances or swellings, suggesting the former were more stable on the seafloor. However, unlike the flattened forms, cinctans with high‐relief bodies were able to passively direct flow towards the mouth and associated food grooves, indicating that they were capable of more efficient feeding on particles suspended in the water. This study provides evidence of a previously unknown evolutionary trade‐off between feeding and stability in Cambrian cinctan echinoderms. [ABSTRACT FROM AUTHOR]

Organisms have limited resources available to invest in reproduction, causing a trade‐off between the number and size of offspring. One consequence of this trade‐off is the evolution of disparate egg sizes and, by extension, developmental modes. In particular, echinoid echinoderms (sea urchins and sand dollars) have been widely used to experimentally manipulate how changes in egg size affect development. Here, we test the generality of the echinoid results by (a) using laser ablations of blastomeres to experimentally reduce embryo energy in the asteroid echinoderms (sea stars), Pisaster ochraceus and Asterias forbesi and (b) comparing naturally produced, variably sized eggs (1.7‐fold volume difference between large and small eggs) in A. forbesi. In P. ochraceus and A. forbesi, there were no significant differences between juveniles from both experimentally reduced embryos and naturally produced eggs of variable size. However, in both embryo reduction and egg size variation experiments, simultaneous reductions in larval food had a significant and large effect on larval and juvenile development. These results indicate that (a) food levels are more important than embryo energy or egg size in determining larval and juvenile quality in sea stars and (b) the relative importance of embryo energy or egg size to fundamental life history parameters (time to and size at metamorphosis) does not appear to be consistent within echinoderms. [ABSTRACT FROM AUTHOR]

The Great Ordovician Biodiversification Event (GOBE) refers to one of the greatest increases in biodiversity during the Phanerozoic. Recent studies have shown that this taxonomic increase can be attributed to elevated origination rates around the Dapingian–Darriwilian boundary in the Middle Ordovician, while extinction rates stayed relatively constant throughout the Ordovician. Even though this global pattern of origination and extinction appears similar across diverse groups and geographical areas, earlier studies suggested that hard substrate taxa may have diversified prior to the GOBE, during the Early Ordovician. Here, we quantify Ordovician diversification dynamics of hard substrate taxa while simultaneously accounting for temporally varying sampling probabilities. Diversification rates of hard substrate taxa, both as a whole and when analysed as separate groups, appear to be very similar to those of free‐living benthic taxa. The observation that the diversification dynamics of many different taxonomic and ecological groups show the same temporal pattern, suggests a common cause of Ordovician diversification dynamics. [ABSTRACT FROM AUTHOR]

The heart urchin Abatus cavernosus shows sexual dimorphism characterized by the development of external brood pouches and the enlargement of gonopores in brooding females. Relationships between body size, gonopore size, and gonadal maturation in each sex were examined for inflection points using piecewise regression models (PRM). Opening of the gonopore occurred at 15.5 mm test length. Inflection points in the gonadal growth and gonopore diameter trajectories were clustered at smaller sizes in males (23 and 24.2 mm, respectively) than in females (25.1 and 25.9 mm), indicating sex‐specific differences in sexual maturation. Gonopore growth showed positive allometry at pre‐adult stages of development in both sexes, but isometry and negative allometry in adult females and males, respectively. Gonadal growth was initiated at smaller sizes and proceeded at a higher rate with increasing body size in males than in females. Identification of inflection points in gonopore and gonadal growth trajectories, using objective PRM, allows the determination of life stages and sexual maturation for individuals, thus providing a complementary tool for population studies. [ABSTRACT FROM AUTHOR]

Eublastoids are a large clade of blastoids; stemmed blastozoan echinoderms diagnosed by their conservative body plan (three basals, four deltoid plates and five radial plates), lancet plate supporting the ambulacra, and hydrospire respiratory structures. Although Eublastoidea was a highly successful clade in the middle and late Palaeozoic it is absent from early echinoderm radiations seen in the Cambrian and Ordovician record. Here we provide a re‐evaluation of Macurdablastus uniplicatus Broadhead from the Ordovician, using detailed morphological assessment based on advanced synchrotron tomography and phylogenetic analysis. Macurdablastus uniplicatus falls outside Eublastoidea because of the morphological differences in lancet plate and respiratory structures. The oldest recorded eublastoid is thus middle Silurian in age. The re‐evaluation of the morphology of Macurdablastus provides a basis for revising blastoid phylogeny and classification. [ABSTRACT FROM AUTHOR]

Olfactomedins are a family of modular proteins found in multicellular organisms that all contain five‐bladed β‐propeller olfactomedin (OLF) domains. In support of differential functions for the OLF propeller, the available crystal structures reveal that only some OLF domains harbor an internal calcium‐binding site with ligands derived from a triad of residues. For the myocilin OLF domain (myoc‐OLF), ablation of the ion‐binding site (triad Asp, Asn, Asp) by altering the coordinating residues affects the stability and overall structure, in one case leading to misfolding and glaucoma. Bioinformatics analysis reveals a variety of triads with possible ion‐binding characteristics lurking in OLF domains in invertebrate chordates such as Arthropoda (Asp–Glu–Ser), Nematoda (Asp–Asp–His) and Echinodermata (Asp–Glu–Lys). To test ion binding and to extend the observed connection between ion binding and distal structural rearrangements, consensus triads from these phyla were installed in the myoc‐OLF. All three protein variants exhibit wild‐type‐like or better stability, but their calcium‐binding properties differ, concomitant with new structural deviations from wild‐type myoc‐OLF. Taken together, the results indicate that calcium binding is not intrinsically destabilizing to myoc‐OLF or required to observe a well ordered side helix, and that ion binding is a differential feature that may underlie the largely elusive biological function of OLF propellers. [ABSTRACT FROM AUTHOR]

Life traits such as reproductive strategy can be determining factors of species evolutionary history and explain the resulting diversity patterns. This can be investigated using phylogeographic analyses of genetic units. In this work, the genetic structure of five asteroid genera with contrasting reproductive strategies (brooding: Diplasterias, Notasterias and Lysasterias versus broadcasting: Psilaster and Bathybiaster) was investigated in the Southern Ocean. Over 1,400 mtDNA cytochrome C oxidase subunit I (COI) sequences were analysed using five species delineation methods (ABGD, ASAP, mPTP, sGMYC and mGMYC), two phylogenetic reconstructions (ML and BA), and molecular clock calibrations, in order to examine the weight of reproductive strategy in the observed differences among phylogeographic patterns. We hypothesised that brooding species would show higher levels of genetic diversity and species richness along with a clearer geographic structuring than broadcasting species. In contrast, genetic diversity and species richness were not found to be significantly different between brooders and broadcasters, but broadcasters are less spatially structured than brooders supporting our initial hypothesis and suggesting more complex evolutionary histories associated to this reproductive strategy. Broadcasters' phylogeography can be explained by different scenarios including deep‐sea colonisation routes, bipolarity or cosmopolitanism, and sub‐Antarctic emergence for the genus Bathybiaster; Antarctic‐ New Zealand faunal exchanges across the Polar Front for the genus Psilaster. Brooders' phylogeography could support the previously formulated hypothesis of a past trans‐Antarctic seaway established between the Ross and the Weddell seas during the Plio‐Pleistocene. Our results also show, for the first time, that the Weddell Sea is populated by a mixed asteroid fauna originating from both the East and West Antarctic. [ABSTRACT FROM AUTHOR]

While the study of dispersal and connectivity in the ocean typically centres on pelagic species and planktonic larval stages of benthic species, the present work explores an overlooked locomotor means in post‐settlement benthic stages that redefines their dispersal potential.Members of the echinoderm class Holothuroidea colonize a diversity of marine environments world‐wide, where they play key ecological and economical roles, making their conservation a priority. Holothuroids are commonly called sea cucumbers or sea slugs to reflect their slow movements and are assumed to disperse chiefly through pelagic larvae.The present study documents and explores their unexpected ability to actively modify their buoyancy, leading them to tumble or float at speeds orders of magnitudes faster than through benthic crawling. Two focal species representing different taxonomic orders, geographic distributions and reproductive strategies were studied over several years.Active buoyancy adjustment (ABA) was achieved through a rapid increase in water‐to‐flesh ratio by up to 740%, leading to bloating, and simultaneously detachment from the substrate. It occurred as early as 6 months post settlement in juveniles and was recorded in wild adult populations. In experimental trials, ABA was triggered by high conspecific density, decreasing salinity and increasing water turbidity. Based on field video footage, ABA‐assisted movements generated speeds of up to 90 km/day.These findings imply that displacement during planktonic larval stages may not supersede the locomotor capacity of benthic stages, challenging the notion of sedentarity. Combining the present results and anecdotal reports, ABA emerges as a generalized means of dispersal among benthic animals, with critical implications for world‐wide management and conservation of commercially and ecologically significant species. [ABSTRACT FROM AUTHOR]

There are limited acute toxicity test methods for native North American marine species that are considered zooplankton for their entire life cycle. Examples of standardized marine zooplankton methods include mussel, bivalve, and echinoderm development tests that use a relatively short‐lived planktonic larval stage, chronic life‐cycle toxicity tests using epibenthic copepods, and a 24‐h Acartia tonsa copepod test method. The objectives of the present study were to: 1) develop and evaluate a novel, 48‐h acute toxicity test method using the marine North American copepod Pseudodiaptomus pelagicus that is planktonic for its entire life cycle, and 2) determine the sensitivity of P. pelagicus relative to commonly tested marine toxicity test species. The average (±1 standard deviation) median lethal concentrations (LC50s) for copper (Cu), phenanthrene, and un‐ionized ammonia were 32 ± 15 µg/L, 161 ± 51 µg/L, and 1.08 ± 0.30 mg NH3/L, respectively. These results placed P. pelagicus on the more sensitive end of Cu and phenanthrene species sensitivity distributions. The copepod was less sensitive to un‐ionized ammonia than commonly tested marine species. This finding suggests that the acute P. pelagicus test method will allow a focus on assessing the impacts of persistent contaminants of concern with less confounding impact from naturally occurring ammonia released to the water from sources such as suspended sediments. Environ Toxicol Chem 2019;38:1221–1230. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. [ABSTRACT FROM AUTHOR]

Despite the apparent simplicity of the body organization of echinoderms, their immune system is competent to perform a complex innate immune response, which is far from being well understood. The echinoderms represent the most advanced invertebrates that form a bridge with the primitive chordates. In fact, they possess numerous receptors and effectors that are used to obtain a fast immune response. After an infection, the humoral and cellular immune response determines a network in which the main protagonists are membrane and endosomal receptors. The recognition of nonself molecules by specific membrane receptors triggers the immune response, stimulating consecutive intracellular events. We have previously shown how the polyinosinic–polycytidylic acid (polyI:C) that mimics a viral infection is able to induce an immune response in the sea urchin Paracentrotus lividus immune cells. It activates a specific membrane receptor belonging to the Toll‐like receptor (TLR) family. Here, we show the activated expression pattern of some genes involved in the downstream cascade of TLR signalling pathway, such as Pl‐Tbk and Pl‐Irf, whose partial sequence was isolated from P. lividus immune cells. Their mRNA expression increases consequentially to the polyI:C stimulation and in a temporal way. In addition, we analysed the expression of Pl‐NF‐kB and we found that its upregulation was time‐dependent, preceding Pl‐Tbk and Pl‐Irf increase. Protein analysis showed that also some cytokine (TNF‐α and IL‐1α) expression increased after polyI:C insult. Therefore, the purpose of this study was to discover the molecular mechanisms of the innate defence strategies, similarly to vertebrates, implemented by the sea urchins in order to cope with viral infection challenge. [ABSTRACT FROM AUTHOR]

Order Diplobathrida is a major clade of camerate crinoids spanning the Ordovician–Mississippian, yet phylogenetic relationships have only been inferred for Ordovician taxa. This has hampered efforts to construct a comprehensive tree of life for crinoids and develop a classification scheme that adequately reflects diplobathrid evolutionary history. Here, I apply maximum parsimony and Bayesian phylogenetic approaches to the fossil record of diplobathrids to infer the largest tree of fossil crinoids to date, with over 100 genera included. Recovered trees provide a framework for evaluating the current classification of diplobathrids. Notably, previous suborder divisions are not supported, and superfamily divisions will require significant modification. Although numerous revisions are required for families, most can be retained through reassignment of genera. In addition, recovered trees were used to produce phylogeny‐based estimates of diplobathrid lineage diversity. By accounting for ghost lineages, phylogeny‐based richness estimates offer greater insight into diversification and extinction dynamics than traditional taxonomy‐based approaches alone and provide a detailed summary of the ~150 million‐year evolutionary history of Diplobathrida. This study constitutes a major step toward producing a phylogeny of the Crinoidea and documenting crinoid diversity dynamics. In addition, it will serve as a framework for subsequent phylogeny‐based investigations of macroevolutionary questions. [ABSTRACT FROM AUTHOR]

Binocalix dichotomus gen. et sp. nov. is the first British Ordovician aristocystitid diploporite to be named. It is known from a single holotype that is partly disarticulated and incomplete. Nevertheless, it differs from all previously described aristocystitids in having a pair of relatively large ambulacral facets developed above a smooth ambulacral platform and on a single circum‐oral plate. When densely developed, the diplopores become polygonal and have a central tubercle. They closely resemble those of the sphaeronitid subgenus Sphaeronites (Peritaphros), but all species of Sphaeronites s.l. have narrow ambulacral grooves ending in small facets. The similarities in the diplopores are thought to be convergent. Among aristocystitids, only "Calix" inornatus and Triamara are known to have paired ambulacral facets developed on single circum‐oral plates. The former differs from Binocalix in having a smooth thecal surface and flush ambulacral facets. Triamara has raised ambulacral facets but lacks the distinctive ambulacral platforms found in Binocalix. Its diplopores always lack central tubercles, and currently it is only known from the Silurian. [ABSTRACT FROM AUTHOR]

Recent debates over the evolutionary relationships of early echinoderms have relied heavily on morphological evidence from the feeding ambulacral system. Eumorphocystis, a Late Ordovician diploporitan, has been a focus in these debates because it bears ambulacral features that show strong morphological similarity to early crinoid arms. Undescribed and well‐preserved specimens of Eumorphocystis from the Bromide Formation (Oklahoma, USA) provide new data illustrating that composite arms supported by a radial plate that bear a triserial arrangement of axial and extraxial components encasing a coelomic extension can also be found in blastozoans. Previous reports have considered these arm structures to be restricted to crinoids; these combined features have not been previously observed in blastozoan echinoderms. Phylogenetic analyses suggest that Eumorphocystis and crinoids are sister taxa and that shared derived features of these taxa are homologous. The evidence from the arms of Eumorphocystis suggests that crinoid arms were derived from a specialized blastozoan ambulacral system that lost feeding brachioles and strongly suggests that crinoids are nested within blastozoans. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aim: The Antarctic Circumpolar Current (ACC) connects benthic populations by transporting larvae around the continent, but also isolates faunas north and south of the Antarctic Convergence. We test circumpolar panmixia and dispersal across the Antarctic Convergence barrier in the benthic sea star Glabraster antarctica. Location: The Southern Ocean and south Atlantic Ocean, with comprehensive sampling including the Magellanic region, Scotia Arc, Antarctic Peninsula, Ross Sea, and East Antarctica. Methods: The cytochrome c oxidase subunit I (COI) gene (n = 285) and the internal transcribed spacer region 2 (ITS2; n = 33) were sequenced. We calculated haplotype networks for each genetic marker and estimated population connectivity and the geographic distribution of genetic structure using ΦST for COI data. Results: Glabraster antarctica is a single circum‐Antarctic species with instances of gene flow between distant locations. Despite the homogenizing potential of the ACC, population structure is high (ΦST = 0.5236), and some subpopulations are genetically isolated. Genetic breaks in the Magellanic region do not align with the Antarctic Convergence, in contrast with prior studies. Connectivity patterns in East Antarctic sites are not uniform, with some regional isolation and some surprising affinities to the distant Magellanic and Scotia Arc regions. Main conclusions: Despite gene flow over extraordinary distances, there is strong phylogeographic structuring and genetic barriers evident between geographically proximate regions (e.g., Shag Rocks and South Georgia). Circumpolar panmixia is rejected, although some subpopulations show a circumpolar distribution. Stepping‐stone dispersal occurs within the Scotia Arc but does not appear to facilitate connectivity across the Antarctic Convergence. The patterns of genetic connectivity in Antarctica are complex and should be considered in protected area planning for Antarctica. Phylogeographic patterns in Glabraster antarctica show high genetic structure in a broadly distributed circumpolar species. There are several instances of connectivity occurs over large geographic distances, suggesting that currents and other abiotic factors play an important role in the distribution of subpopulations. [ABSTRACT FROM AUTHOR]

Articulated ophiocistioids are rare as fossils, enigmatic in terms of their phylogenetic position, and have been considered to be an exclusively Palaeozoic echinoderm group. Apart from articulated body fossils, the fossil record of Ophiocistioidea is otherwise dependent on isolated microfossils. However, it has been demonstrated that disarticulated jaw elements (goniodonts) of ophiocistioids can be diagnostic at genus and species level and can be used to fill gaps in the non‐articulated fossil record. The Late Triassic Cassian Formation of Italy is regarded as one of the most important strata of early Mesozoic invertebrates worldwide. A fossil assemblage from a locality near Misurina, South Tyrol, yielded various echinoderms, including a stem group echinoid representative and a new ophiocistioid, Linguaserra triassica sp. nov. The new taxon is described and placed within linguaserrid ophiocistioids. The evolutionary history of the group is briefly discussed in relation to other taxa of the Ophiocistioidea and Echinoidea. Linguaserra triassica not only represents the first documented occurrence of this 'Palaeozoic' echinoderm class from Mesozoic strata but also establishes the stratigraphically youngest record of goniodonts or ophiocistioid teeth in the world. [ABSTRACT FROM AUTHOR]

Aim: We demarcate marine benthic global bioregions based on fossil and recent occurrence data. Our main goal is to compare past and present biogeography and to extract major abiotic drivers of biogeographical patterns. We specifically test the hypothesis that global biogeography has changed markedly after the climatic fluctuations of the past 10 Myr. Location: Worldwide. Time period: Recent; late Miocene–Pleistocene interval. Major taxa studied: Benthic taxa with a rich fossil record: Bivalvia, Brachiopoda, Bryozoa, Gastropoda, Echinodermata, Decapoda and reef corals. Methods: We use occurrence data from the Ocean Biogeographic Information System (OBIS) and the Paleobiology Database to construct compositional networks and outline objective marine bioregions of benthic marine invertebrates using the "infomap" community detection algorithm. We assess the association of modern bioregions with a variety of environmental parameters by applying multivariate statistical analyses, such as principal components analysis, random forests and multiple logistic regressions. Results: Recent first‐order bioregions for the coastal ocean are, in general, consistent across all taxa. Seawater temperature surpasses nutrients, primary production and salinity as a predictor of modern bioregion distributions. Despite substantial climatic variations, late Cenozoic biogeographical patterns recorded in fossils are very similar to modern ones. Main conclusions: Biogeographical boundaries within oceans are strongly controlled by temperature gradients, but open oceanic and continental barriers determine the global biogeographical structure. The joint structure of a landmass distribution, deep ocean basins and the latitudinal temperature gradient defines bioregionalization of the benthic marine habitat, which did not change substantially over the past 10 Myr. [ABSTRACT FROM AUTHOR]

Abstract: Hierarchical solution self‐assembly has become an important biomimetic method to prepare highly complex and multifunctional supramolecular structures. However, despite great progress, it is still highly challenging to prepare hierarchical self‐assemblies on a large scale because the self‐assembly processes are generally performed at high dilution. Now, an emulsion‐assisted polymerization‐induced self‐assembly (EAPISA) method with the advantages of in situ self‐assembly, scalable preparation, and facile functionalization was used to prepare hierarchical multiscale sea urchin‐like aggregates (SUAs). The obtained SUAs from amphiphilic alternating copolymers have a micrometer‐sized rattan ball‐like capsule (RBC) acting as the hollow core body and radiating nanotubes tens of micrometers in length as the hollow spines. They can capture model proteins effectively at an ultra‐low concentration (ca. 10 n m) after functionalization with amino groups through click copolymerization. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the mechanisms with which organisms can respond to a rapidly changing ocean is an important research priority in marine sciences, especially in the light of recent predictions regarding the pace of ocean change in the coming decades. Transgenerational effects, in which the experience of the parental generation can shape the phenotype of their offspring, may serve as such a mechanism. In this study, adult purple sea urchins, Strongylocentrotus purpuratus, were conditioned to regionally and ecologically relevant pCO2 levels and temperatures representative of upwelling (colder temperature and high pCO2) and nonupwelling (average temperature and low pCO2) conditions typical of coastal upwelling regions in the California Current System. Following 4.5 months of conditioning, adults were spawned and offspring were raised under either high or low pCO2 levels, to examine the role of maternal effects. Using RNA‐seq and comparative transcriptomics, our results indicate that differential conditioning of the adults had an effect on the gene expression patterns of the progeny during the gastrula stage of early development. For example, maternal conditioning under upwelling conditions intensified the transcriptomic response of the progeny when they were raised under high versus low pCO2 conditions. Additionally, mothers that experienced upwelling conditions produced larger progeny. The overall findings of this study are complex, but do suggest that transgenerational plasticity in situ could act as an important mechanism by which populations might keep pace with rapid environmental change. [ABSTRACT FROM AUTHOR]

Abstract: Background: The enteric nervous system (ENS) and the central nervous system (CNS) of mammals both contain integrative neural circuitry and similarities between them have led to the ENS being described as the brain in the gut. Purpose: To explore relationships between the ENS and CNS across the animal kingdom. We found that an ENS occurs in all animals investigated, including hydra, echinoderms and hemichordates that do not have a CNS. The general form of the ENS, which consists of plexuses of neurons intrinsic to the gut wall and an innervation that controls muscle movements, is similar in species as varied and as far apart as hydra, sea cucumbers, annelid worms, octopus and humans. Moreover, neurochemical similarities across phyla imply a common origin of the ENS. Investigation of extant species suggests that the ENS developed in animals that preceded the division that led to cnidaria (exemplified by hydra) and bilateria, which includes the vertebrates. The CNS is deduced to be a bilaterian development, later than the divergence from cnidaria. Consistent with the ENS having developed independent of the CNS, reciprocal connections between ENS and CNS occur in mammals, and separate neurons of ENS and CNS origin converge on visceral organs and prevertebral ganglia. We conclude that an ENS arose before and independently of the CNS. Thus the ENS can be regarded as the first brain. [ABSTRACT FROM AUTHOR]

This study documents previously unknown taxonomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event ( GOBE), and their diversification history surrounding the end-Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high-resolution temporal , taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end-Ordovician mass extinction. A Bayesian 'fossil tip-dating' analysis implementing the fossilized birth-death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor-descendant relationship (via 'budding' cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from 'taxocrinid' grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post-Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeographical regions for clade-based phylogenetic studies and improving estimates of global biodiversity through geological time. [ABSTRACT FROM AUTHOR]

A fabrication strategy for biphasic gels is reported, which incorporates high-internal-phase emulsions. Closely packed micro-inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape-memory performance because of the switchable micro- inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self-healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials. [ABSTRACT FROM AUTHOR]

Sea cucumbers are increasingly exploited for human consumption and for their curative properties, and many wild populations are now depleted or in danger of extinction. While aquaculture is seen as an alternative to fisheries and as a mean to restore wild populations, more knowledge is needed on their reproductive strategies to render this practice efficient, notably for fissiparous holothurians, which are some of the mobile animals able of asexual reproduction by transverse fission. Little information is available on their population genetic diversity and structure. Here, the clonal structure of populations of the fissiparous sea cucumber Stichopus chloronotus has been investigated using nine microsatellite loci and a random sampling, at different spatial (intra-reef and inter-reef) and temporal (inter-season and inter-year) scales. Our findings highlight the importance of asexual reproduction in maintaining these populations, and the prevalence of the 'initial seedling recruitment' strategy (ISR), leading to a high stability of clonal composition over seasons and years. It also seemed that clonal propagation was limited to the reef scale (<10 km) while reefs were connected by sexual dispersal. This is the first time that clonal structure in sea cucumbers has been studied at such a fine scale, with a specific sampling strategy. It provides key findings on the genetic diversity and structure of fissiparous sea cucumbers, which will be useful for the management of wild populations and aquaculture. [ABSTRACT FROM AUTHOR]

The body wall of starfish is composed of magnesium calcite ossicles connected by collagenous tissue and muscles and it exhibits remarkable variability in stiffness, which is attributed to the mechanical mutability of the collagenous component. Using the common European starfish Asterias rubens as an experimental animal, here we have employed a variety of techniques to gain new insights into the structure of the starfish body wall. The structure and organisation of muscular and collagenous components of the body wall were analysed using trichrome staining. The muscle system comprises interossicular muscles as well as muscle strands that connect ossicles with the circular muscle layer of the coelomic lining. The collagenous tissue surrounding the ossicle network contains collagen fibres that form loop-shaped straps that wrap around calcite struts near to the surface of ossicles. The 3D architecture of the calcareous endoskeleton was visualised for the first time using X-ray microtomography, revealing the shapes and interactions of different ossicle types. Furthermore, analysis of the anatomical organisation of the ossicles indicates how changes in body shape may be achieved by local contraction/relaxation of interossicular muscles. Scanning synchrotron small-angle X-ray diffraction ( SAXD) scans of the starfish aboral body wall and ambulacrum were used to study the collagenous tissue component at the fibrillar level. Collagen fibrils in aboral body wall were found to exhibit variable degrees of alignment, with high levels of alignment probably corresponding to regions where collagenous tissue is under tension. Collagen fibrils in the ambulacrum had a uniformly low degree of orientation, attributed to macrocrimp of the fibrils and the presence of slanted as well as horizontal fibrils connecting antimeric ambulacral ossicles. Body wall collagen fibril D-period lengths were similar to previously reported mammalian D-periods, but were significantly different between the aboral and ambulacral samples. The overlap/D-period length ratio within fibrils was higher than reported for mammalian tissues. Collectively, the data reported here provide new insights into the anatomy of the body wall in A. rubens and a foundation for further studies investigating the structural basis of the mechanical properties of echinoderm body wall tissue composites. [ABSTRACT FROM AUTHOR]

Sea stars (Echinodermata: Asteroidea) are a key component of Southern Ocean benthos, with 16% of the known sea star species living there. In temperate marine environments, sea stars commonly play an important role in food webs, acting as keystone species. However, trophic ecology and functional role of Southern Ocean sea stars are still poorly known, notably due to the scarcity of large‐scale studies. Here, we report 24,332 trophic marker (stable isotopes and elemental contents of C, N, and S of tegument and/or tube feet) and biometric (arm length, disk radius, arm to disk ratio) measurements in 2,456 specimens of sea stars. Samples were collected between 12 January 1985 and 8 October 2017 in numerous locations along the Antarctic littoral and subantarctic islands. The spatial scope of the data set covers a significant portion of the Southern Ocean (47.717° S to 86.273° S; 127.767° W to 162.201° E; depth, 6–5,338 m). The data set contains 133 distinct taxa, including 72 currently accepted species spanning 51 genera, 20 families, and multiple feeding guilds/functional groups (suspension feeders, sediment feeders, omnivores, predators of mobile or sessile prey). For 505 specimens, mitochondrial CO1 genes were sequenced to confirm and/or refine taxonomic identifications, and those sequences are already publicly available through the Barcode of Life Data System. This number will grow in the future, as molecular analyses are still in progress. Overall, thanks to its large taxonomic, spatial, and temporal extent, as well as its integrative nature (combining genetic, morphological, and ecological data), this data set can be of wide interest to Southern Ocean ecologists, invertebrate zoologists, benthic ecologists, and environmental managers dealing with associated areas. Please cite this data paper in research products derived from the data set, which is freely available without copyright restrictions. [ABSTRACT FROM AUTHOR]

Astropectinid seastars typically develop as either feeding bipinnaria larvae or nonfeeding, barrel-shaped larvae. Understanding the direction and frequency of evolutionary transitions between these larval nutritional modes requires knowledge of the distribution of developmental diversity in the family, but the development of only a few astropectinids is known. Here we describe embryogenesis, larval development, and metamorphosis of Astropecten armatus, an astropectinid common in soft-sediment subtidal habitats in southern California. Adults were reproductively mature all year except during the winter months (December-February). Oocytes averaged 137 μm in diameter, the smallest reported in the genus. Fertilized oocytes developed into feeding bipinnaria larvae that fed in the plankton for at least 4 weeks, and in some cases up to 33 weeks, before metamorphosis. The tube feet of juveniles were adhesive, but lacked suckers, contrary to some previous descriptions of suckered tube feet in the juveniles of paxillosidans. [ABSTRACT FROM AUTHOR]