Echinoid Species Research Articles

Selected regular echinoids (Echinoidea) from the upper Campanian–Maastrichtian along the western borders of the Northern Oman Mountains, with description of a new species

Thirteen species of regular echinoid, in ten genera, are recorded from the upper Campanian–Maastrichtian Qahlah and Simsima formations of two sections located along the western borders of the Northern Oman Mountains. Twelve of these are from the Simsima Formation in the Jebel El Rawdah section, four from the Qahlah and Simsima formations in the Jebel Huwayyah section. One new species, Hattopsis muradi, is described from the Jebel El Rawdah section. The status of the genus Pseudorthopsis is confirmed; differences between it and Orthopsis are discussed and Orthopsis sanfilippoi is transferred to Pseudorthopsis, here being recorded for the first time from the Arabian Gulf region. Revision of three species referred to Hattopsis and nine species ascribed to Protechinus (= Noetlingia, Noetlingaster) has elucidated the relationship between these two genera and affirmed the distinctiveness of Hattopsis. Hattopsis sphericus and Echinotiara perebaskinei are recorded for the first time from Jebel Huwayyah. All species identified are compared with other related taxa, and their stratigraphical ranges, affinities, palaeobiogeography and palaeoecology discussed.

Paucispecific invertebrate associations in the Coniacian (Upper Cretaceous) Essen Formation (Tébessa Mountains, northeast Algeria)

The Coniacian strata of the Tébessa Mountains in northern Algeria are predominantly marly facies that have received few studies. The present study is the first one to be carried out at Djebel Essen (west of Tébessa) to reveal the paleoenvironmental setting. The macrofossil taxa identified herein include fifteen bivalve species, three gastropods, and one cephalopod species, in addition to four irregular echinoid species. Quantitative analysis of these macrofossils indicates the occurrence of three benthic Coniacian macrofaunal associations, which include: 1) Agelasina plenodonta, 2) Cucullaea, and 3) Oscillopha-Plicatula. Both Agelasina plenodonta and Cucullaea associations are dominated by infauna. However, Cucullaea Association contains only suspension-feeders, where deposit-feeders are completely absent, suggesting oligotrophic conditions, that might have resulted in the lowest diversity level. In contrast, epifaunal taxa dominated the Oscillopha-Plicatula association. All the three associations are paucispecific. This low diversity of the Coniacian associations at study area and in other North African countries, can be attributed to the retreat of the sea and the shrinking of shallower habitats’ area. Probably, these associations lived within restricted marginal marine environments. The absence of any potential indicator of the middle-upper Coniacian anoxic event (OAE-3) agrees with the case in nearby sections and confirms a restricted extent of this event. The occurrence of many taxa of either regional or cosmopolitan affinity suggests episodic connection with the Tethyan Ocean.

Albian–Cenomanian echinoids from areas north of Bandar Abbas and south of Fars in the Zagros Mountains, Iran

Fossil echinoids have rarely been described from Iran. This study focuses on the echinoid fauna found in the Cretaceous strata (Kazhdumi Formation) of the Geno and Gerash sections in the Bandar Abbas and Fars areas of the Zagros Mountains, southern Iran. The age of the Kazhdumi Formation in both sections is determined to be Albian-Cenomanian based on the associated ammonites and microfauna, its stratigraphic position, and previous studies on this formation. Twenty-one echinoid species (twelve regular and nine irregular) belonging to seventeen genera were described in this study. Fourteen of these species are reported for the first time from Iran. In addition, a new diadematoid echinoid species, Arabicodidema jafariani sp. nov. is introduced. New age ranges are proposed for Pliotoxaster comanchei and Lambertiaster douvillei. The paleogeographic position of the Zagros Basin in the Tethyan realm is confirmed based on the distribution of the index species.

Calcium-rich seawater affects the mechanical properties of echinoderm skeleton

Shifts in the magnesium to calcium ratio of seawater in the geological history are thought to have profoundly affected biomineralization of marine invertebrates, including some echinoderms, which changed their skeletal mineralogy from high-magnesium to low-magnesium calcite and vice versa. Here we report on experiments that aimed to investigate the effect of ambient seawater magnesium to calcium ratio on magnesium to calcium ratio and nanomechanical properties in the spines of two echinoid species (Arbacia lixula and Paracentrotus lividus). We found that echinoids cultured in seawater with a low magnesium to calcium ratio produced a skeleton with lower both magnesium content and nanohardness than those of the control specimens incubated under normal (high) magnesium to calcium ratio conditions. These results may suggest that at certain times in the geological past (during the so-called calcite seas) sea urchins with decreased skeletal magnesium contents were more susceptible to damage due to physical disturbances, predation and post-mortem taphonomic processes. Increased skeletal hardness of echinoids from the so-called aragonite seas is expected to enhance their taphonomic potential, thus, to some extent, mitigates the preservation bias related to increased solubility of high-magnesium calcite.

Catalogue of the Echinoidea (sea urchins, phylum Echinodermata) collected by the IN2021_V04 and IN2022_V08 expeditions to the Australian Christmas Island and Cocos (Keeling) Islands Territories

In this catalogue, the 17 species of echinoids collected by the IN2021_V04 and IN2022_V08 expeditions to the Australian Christmas Island and Cocos (Keeling) Islands Territories are described and illustrated.

Combining Morphological Characteristics and DNA Barcoding Techniques Confirm Sea Urchins of the Genus Echinometra (Echinodermata: Echinoidea) in Marine Habitat Located at Extreme Regions of the Caribbean Sea.

Echinometra spp. are pantropical echinoids found in benthic marine habitat throughout the Caribbean, Atlantic, and Indo-West Pacific oceanic regions. Currently, morphology and molecular data are sparse for echinoids observed along the northeastern coast of Toco, Trinidad, where they are relatively common. Additionally, accurate species identity for Echinometra spp. remains dynamic at both northernmost and southernmost parts of the Caribbean Sea. Although distribution of sea urchins in the genus Echinometra have extensively been studied throughout the Atlantic and Indo-West Pacific, information on its range of distribution at the edge of the Caribbean Sea is lacking. In this study, the mitochondrial Cytochrome c Oxidase subunit I (mt COI) gene was amplified using polymerase chain reaction, then sequenced. Based on successfully obtained gene sequences for 581 base pairs, the echinoid species Echinometra lucunter and Echinometra viridis were identified for black and red color morphotypes from Trinidad (n=23) and Key Largo, Florida (n=6), respectively. Furthermore, these specimens were genetically identical to species identified in other studies for Puerto Rico, Panamá, Honduras, and Belize. Although morphological variations, such as spine and test color occur throughout Echinometra spp., molecular identification using the barcoding technique confirmed E. lucunter color morphs for the first time in Trinidad. Since the status of E. lucunter populations, specifically at the most northern and southern regions of the Caribbean Sea is dynamic, further studies using gene markers are essential in determining species distribution, in light of current trends in climate change.

Invertebrate fauna of the Albian–Lower Cenomanian deposits in the Fars and Isfahan provinces (Firuzabad and Fasakhod sections), Zagros Basin, Central Iran

The Albian- Cenomanian deposits of the Kazhdumi Formation at Zagros Basin (Firuzabad section and Central Iran (Fasakhod section), represents a carbonate sedimentary succession and contain rich and diverse invertebrate macro fauna. Detailed studies on about 200 specimens of invertebrate macro fauna revealed from two stratigraphic intervals led to recognition of 5 species of gastropods; (Liopeplum? sp., Columbellina sp., Cryptaulax? sp., Turritella? sp., Pleurotomaria sp.), 3 species of ammonites; (Knemiceras duberterti, Sphenodiscus sp., Knemiceras persicum), 10 species of bivalves assemblages; (Ceratostreon flabellatum, Cardium? sp., Exogyra (Costagyra) olisiponensis, Neithea (Neithea) quinquecostata, Trigonia sp., Buchia? sp., Cardium? sp., Pseudogyra sp., Ontaria? sp., Nucula? sp., Pleuromia? sp., 1 species of echinoids; Dorocidaris taouzensis with a prolific horizon of Notopocorystes xizangensis of raninoid crabs. The absence of large gastropods and bivalves fauna and abundance of suspension-feeders indicated instability of the substrate, shallow marine paleoenvironment.and a medium energy condition.

Formulated feeds prolong the reproductive period of a cultured echinoid

AbstractObjectiveThe production of echinoid larvae and juveniles is required in both wild‐population enhancement programs and full life‐cycle culture. Many echinoid species of commercial interest spawn only once or twice a year, however, restricting temporal access to viable broodstock. High‐energy/high‐protein formulated feeds have been used for gonad enhancement of a variety of echinoid species, but the goal of that activity has always been to produce premature gonads, which the market requires, not the production of mature gonads for breeding. The present investigation, originally established to examine gonad enhancement, took advantage of a spawning event to assess the efficacy of a formulated feed to extend the spawning period or reduce gonad recovery time after spawning in a commercially relevant echinoid, the green sea urchin Strongylocentrous droebachiensis.MethodsUrchins held in suspended sea cages were fed either a formulated, commercial, pelleted urchin diet or bull kelp Nereocystis luetkeana over 12 weeks, with survival, somatic growth, gonad quantity (wet weight, yield), and gonad quality (presence/absence of gametes) being examined over time.ResultSurvivorship after 12 weeks was high, little difference being observed between the two diets (mean ± SE: 98.2 ± 1.1% and 95.9 ± 1.9% for kelp and formulated feed, respectively). There was no significant difference in somatic growth between the two treatments, but the formulated feed led to significantly higher gonad wet weight and yield than kelp at the end of the study. When compared with kelp, the formulated feed may have led to earlier spawning and quicker gonad recovery and prevented the complete spawning of all urchins, thus extending the period of gamete availability.ConclusionFormulated feeds may have the potential to maintain reproductively active broodstock over an extended time, allowing expansion of the period in which echinoid larvae and juveniles can be produced.

Fishes associating with the echinoids Diadema setosum and Echinothrix calamaris (Diadematoida: Diadematidae) in the Phi Phi Islands of southwestern Thailand

Many fish species are known to associate with echinoids. We studied the frequency of fishes associating with the diadematid Black Longspine Urchin Diadema setosum and Banded Sea Urchin Echinothrix calamaris in the Phi Phi Islands of southwestern Thailand during July 17–20, 2022. A total of 1373 fish individuals of 20 species associated with 1157 D. setosum, and 11 fish individuals of seven species associated with 76 E. calamaris. The proportion of fish individuals per echinoid host was 8.2 times higher for longer-spined D. setosum (1.19) than for E. calamaris (0.14), and the proportion of echinoids hosting one or more fish was 2.5 times higher for D. setosum (22.9%) than for E. calamaris (9.2%), supporting the hypothesis that fishes prefer to associate with echinoid species with the longest spines, which potentially provide more protection against predators. All fishes associating with echinoids were small (<10 cm); most were adults, but for some species, all were juveniles. All fishes were facultative associates of echinoids. Only three fish species had been previously reported associating with D. setosum and none with E. calamaris; the remaining fish species represent new records of association, including 17 for D. setosum and seven for E. calamaris.

Cretaceous echinoids in Paleocene reworked tsunamite from Coahuila, NE Mexico

The Maastrictian echinoid species Hardouninia mortonis (Michelin, 1850) typical from Upper Cretaceous deposits along the Gulf and Atlantic Coastal plains of USA and Canada, is here reported for the first time for Mexico into a peculiar matrix, which consists of a K/Pg reworked tsunamite deposited during an early Paleocene storm event in the NW portion of the Parras Basin, Difunta Group, NE Mexico. Our specimens have a peculiar small size compared with those reported for Maastrichtian localities in Mississippi amd North Carolina. Small-sized specimens are abundant in late Maastrichtian Las Encinas Formation of the Parras Basin, and are identical to the more than 50 specimens found included in reworked K/Pg tsunamite at Arroyo Amargos, Coahuila. Our interpretation is that the tsunamite was reworked during an early Paleocene storm, forming a channel-like structure of microconglomeratic sandstone, which includes ammonites (Sphenodiscus pleurisepta), the small Hardouinia mortonis, and delicate early Paleocene ostreoids. Other localities with reworked K/Pg tsunamite deposits are found in the adjacent La Popa Basin, interpreted also as deposited by early Paleocene storms in this area of NE Mexico, in Coahuila and Nuevo León states, but mix of Maastrichtian and Paleocene invertebrates has only been observed in Amargos.

EQUINOIDES DA FORMAÇÃO JANDAÍRA, CRETÁCEO SUPERIOR DA BACIA POTIGUAR, NORDESTE DO BRASIL: ESTADO DA ARTE

Echinoids from Jandaíra Formation, Upper Cretaceous, Potiguar Basin, Northeastern Brazil. The present paper analyzes the studies about fossil echinoids from the Jandaíra Formation, Upper Cretaceous, Potiguar Basin, Northeastern Brazil, with the purpose of showing the current knowledge about the species of the geological unit. The bibliography was obtained by searching websites such as Scholar Google, Memória da Biblioteca Nacional, Biodiversity Heritage Library, and Periódicos Capes. Furthermore, we contacted several researchers in the area of study, looking for access to any missing bibliography. We surveyed 32 studies, including monographs, dissertations, abstracts, papers in scientific journals, and book chapters. A timeline was produced for each species. We concluded that are fourteen valid species for the formation: Petalobrissus lehugeurae Alves; Petalobrissus setifensis Cotteau; Petalobrissus cubensis Weisbord; Mecaster texanus Roemer; Mecaster fourneli Agassiz &amp; Desor; Hemiaster cearensis Brito; Hemiaster catandubensis Maury; Mecaster sp.; Rosadosoma riograndensis (Maury); Phymosoma major Coquand; Goniopygus durandi Perón &amp; Gauthier; Coenholectypus upanemensis Beurlenou, Coenholectypus serialis sp.?; Phymosoma sp.; and Pygorhynchus sp.?. A considerable diversity. However, apart from taxonomy, few studies address other subjects such as paleoecology, taphonomy, biogeography, and stratigraphy. The observations raised, help to understand the taxonomic history of the echinoid species. Accordingly, they might indicate the direction of future studies about echinoids of the Jandaíra Formation. Keywords: Echinodermata, Echinoidea, Taxonomy, Upper Cretaceous.

Santonian (Late Cretaceous) echinoids from the Santander area (northern Cantabria, Spain)

Eight echinoid species are described from Upper Cretaceous marl-limestone alternations from a temporary outcrop in the neighbourhood of the village of Mompia (northern Cantabria, Spain): Temnocidaris (Stereocidaris) mengaudi, Pseudoholaster pachecoi, Roweaster cantaber, Micraster turonensis, Micraster mengaudi, Bolbaster micranthus and two newly described species: the phymosomatoid Cosmocyphus cantaber sp. nov. and the micrasterid Micraster quebrada sp. nov. The three Micraster species reveal an astonishing and extreme degree of intraspecific variation, in particular the degree of inflation of the test. This has not yet been detected in any other spatangoid species before. The majority of reported echinoids are restricted to the working area, and hence are likely endemic to this area. An integrated stratigraphic approach using ammonites, inoceramid bivalves, calcareous nannofossils and stable carbon isotopes localises the echinoid assemblage in the upper middle and lower upper Santonian.

The morphologic and paleobiogeographic implications of a new early Silurian echinoid from Anticosti Island, Quebec, Canada

The Ordovician and Silurian are an exceptionally important interval of time for understanding the effects of ancient climate change on the paleobiodiversity of echinoderms. Despite this importance, the fossil record of many echinoderm groups during this interval is sparse. The echinoids, or sea urchins, are no exception; and new fossil finds are necessary to better understand their initial diversification during the lower Paleozoic. We herein report on material from a new genus and species of echinoid, Anticostiechinus petryki gen. et sp. nov., from the Silurian of Anticosti Island, Canada. The morphology of the tubercles and spines of A. petryki are atypical for echinoids, and the surfaces for spine articulation consist of rounded, concave indentations. Additionally, the bases of the spines are subspherical. Furthermore, A. petryki belongs to the family Echinocystitidae, which increases the known diversity and distribution of this family during the Silurian and provides insight into the biogeography of echinocystitids from the Silurian to Devonian.

The role of the length spines of echinoids in their association with crustacean and fish in Los Cabos, Baja California Sur, Mexico

Introduction: Echinoids (sea urchins) provide shelter for a variety of facultative or obligatory ectosymbionts. Objective: To evaluate the hypothesis that decapods and fishes prefer to associate with echinoid individuals and species that have longer spines. Methods: We visually studied the frequency of decapod crustaceans and fishes associated with echinoids in shallow water (&lt; 4 m) and deeper water (5-20 m) at Los Cabos, Baja California Sur, Mexico, during 1-6 January 2019. Results: We inspected 1 058 echinoids of six species. Five decapod species associated with three species of echinoids. When compared with other echinoid species, in shallow water, decapods associated 5.1 times more often with the longest-spined echinoid Diadema mexicanum (7.0 times more decapods per individual D. mexicanum); in deeper water, association frequency was similar for all echinoid species. Fourteen fish species associated with four echinoid species. In shallow water, fishes associated 2.6 times more with D. mexicanum (4.5 times more fishes per individual). There was no preferred echinoid species in deeper water. Longer-spined D. mexicanum had more decapods and fishes. Associations were more frequent in shallow water. Multiple individuals and species of decapods and fish often associated together with a single D. mexicanum. The decapod that presumably is Tuleariocaris holthuisi showed a possible obligatory association with one of the equinoids (D. mexicanum); the other decapods and all fish species are facultative associates. Conclusion: Our results support the hypothesis that decapods and fishes associate most frequently with echinoid with the longest spines, presumably to reduce the risk of predation.

Spatial distribution, diversity, and taphonomy of clypeasteroid and spatangoid echinoids of the central Florida Keys.

Irregular echinoids are ecosystem engineers with diverse functional services. Documenting present-day distribution of those widespread organisms is important for understanding their ecological significance and enhancing our ability to interpret their rich fossil record. This study summarizes SCUBA surveys of clypeasteroid and spatangoid echinoids conducted in 2020 and 2021 along the central part of the Florida Keys. The survey included observations on both live and dead specimens, their distribution, habitat preferences, abundance, and live-dead comparison. Echinoids were found at 17 out of 27 examined sites (63%) and occurred across a wide range of habitats including coastal seagrass meadows, subtidal sand and seagrass settings of the Hawk Channel, backreef sands, and fine muddy sands of deeper forereef habitats. The encountered species, both dead and alive, included Clypeaster rosaceus (four sites), Clypeaster subdepressus (five sites), Encope michelini (three sites), Leodia sexiesperforata (eight sites), Meoma ventricosa (nine sites), and Plagiobrissus grandis (four sites). All sites were dominated by one species, but some sites included up to five echinoid species. Live-dead fidelity was high, including a good agreement in species composition of living and dead assemblages, congruence in species rank abundance, and overlapping spatial distribution patterns. This high fidelity may either reflect long-term persistence of local echinoid populations or fragility of echinoid tests that could prevent post-mortem transport and the formation of time-averaged death assemblages. Regardless of causative factors, the live-dead comparisons suggest that irregular echinoid assemblages, from settings that are comparable to the study area, may provide a fossil record with a high spatial and compositional fidelity. The survey of live fauna is consistent with past regional surveys in terms of identity of observed species, their rank abundance, and their spatial distribution patterns. The results suggest that despite increasingly frequent hurricanes, active seasonal fisheries, massive tourism, and urban development, irregular echinoids continue to thrive across a wide range of habitats where they provide diverse ecosystem services by oxygenating sediments, recycling organic matter, supporting commensal organisms, and providing food to predators. Results reported here document the present-day status of local echinoid populations and should serve as a useful reference point for assessing future regional changes in echinoid distribution and abundance.

A Chromosome-level Genome Assembly of the Highly Heterozygous Sea Urchin Echinometra sp. EZ Reveals Adaptation in the Regulatory Regions of Stress Response Genes.

Echinometra is the most widespread genus of sea urchin and has been the focus of a wide range of studies in ecology, speciation, and reproduction. However, available genetic data for this genus are generally limited to a few select loci. Here, we present a chromosome-level genome assembly based on 10x Genomics, PacBio, and Hi-C sequencing for Echinometra sp. EZ from the Persian/Arabian Gulf. The genome is assembled into 210 scaffolds totaling 817.8 Mb with an N50 of 39.5 Mb. From this assembly, we determined that the E. sp. EZ genome consists of 2n = 42 chromosomes. BUSCO analysis showed that 95.3% of BUSCO genes were complete. Ab initio and transcript-informed gene modeling and annotation identified 29,405 genes, including a conserved Hox cluster. E. sp. EZ can be found in high-temperature and high-salinity environments, and we therefore compared E. sp. EZ gene families and transcription factors associated with environmental stress response (“defensome”) with other echinoid species with similar high-quality genomic resources. While the number of defensome genes was broadly similar for all species, we identified strong signatures of positive selection in E. sp. EZ noncoding elements near genes involved in environmental response pathways as well as losses of transcription factors important for environmental response. These data provide key insights into the biology of E. sp. EZ as well as the diversification of Echinometra more widely and will serve as a useful tool for the community to explore questions in this taxonomic group and beyond.

The Growth Zones of Test Plates in Four Spatangoid Echinoid Species: Irregular Pattern.

Whether the growth zone found in the coronal plate of echinoids can be used as a chronometer to estimate the age of individuals is controversial. In spatangoid echinoids, it is not known whether the growth zone formation occurs annually. In this study, the growth zone formation process was examined in four spatangoid species from natural conditions. In Nacospatangus alta and Brissus agassizii, the formation of a dark zone indicates the maturity of the gonad and does not necessarily correspond to the age of the individual. In Lovenia elongata, dark growth zones were formed several times per year. Unlike in the other studied species, in Metalia spatagus, the light and dark growth zones appeared to be formed radially, rather than in a ring-like manner. These results may indicate that the frequency and mode of growth zone formation differ across species. As such, it is not appropriate to use the growth zone as a chronometer in spatangoid echinoids. If the growth zone is to be used as an indicator of age, more research is needed about the phase of forming the growth zone in each echinoid species.

The male and female gonad transcriptome of the edible sea urchin, Paracentrotus lividus: Identification of sex-related and lipid biosynthesis genes

Paracentrotus lividus is the most abundant, geographically distributed, and desirable echinoid species in Europe. Although economically important, this species has scarce genomic resources available. Here, we produced and comprehensively characterized the male and female gonad transcriptome of P. lividus. The P. lividus transcriptome assembly has 53,865 transcripts, an N50 transcript length of 1842 bp, and an estimated gene completeness of 97.4% and 95.6% in Eukaryota and Metazoa BUSCO databases, respectively. Differential gene expression analyses yielded a total of 3371 and 3351 up-regulated genes in P. lividus male and female gonad tissues, respectively. Additionally, we analyzed and validated a catalog of transcripts pivotal in sexual development and determination (206 transcripts) as well as in biosynthesis and storage of lipids (119 transcripts) in male and female specimens. This study provides a valuable resource and will contribute to the future conservation of the P. lividus species as well as its exploitation in an aquaculture setting.

Perception of Dissolved Food-Related Compounds by the Sea Urchin Paracentrotus lividus (Echinodermata: Echinoidea)

Echinoid feeding biology is well known but their sluggish responses to chemical stimuli have turned them into inadequately worked in the field of chemoreception. Echinoid responses to chemical stimulation had allowed, so far, only qualitative analyses based on tube-feet activity, directional, or masticatory movements, and artificial agarose foods. Besides stimulation through plumes of dissolved organic compounds and response analysis based on tube-feet activity, we propose another method to chemically stimulate echinoids that allows for fast and unambiguous responses and thus, quantitative analyses. Small squared pieces of absorbent semi-synthetic cleaning cloths, soaked with specific chemical compounds (simulacra), such as water insoluble lipid oils, were deposited singly or concurrently with a blank on the aboral hemisphere of each sea urchin, allowing choice and eventual transport down to the mouth by tube feet and spines of one or both cloths. The responsiveness ofParacentrotus lividuswas clearly dependent on its nutritional state. Well-fed sea urchins (maize whole grains) rarely responded, while the ones fed with less caloric rations (Kombu seaweed) responded faster and objectively. Stimulating sea urchinP. lividuswith 41 different food-related compounds, such as carbohydrates, proteins, peptides and amino acids, oils and fatty acids, and purified chemicals related with some human basic tastes, it was possible to evidence a clear ability of this echinoid species to positively discriminate proteins, starches, and a very few oils. Perceived as incitants/stimulants we have only found among proteins gliadin (from wheat gluten) but not casein (from bovine milk), among polysaccharides starch but not laminarin (from kelp) or glycogen (from mussels), and among lipids only the fatty acid linolenic acid. Among tissues, Kombu alga flesh and mussel flesh were readily perceived as both incitant/stimulant but not Kombu and mussel extracts. Therefore, the combined results reported here provide evidence forP. lividusas an omnivorous species rather than a strictly herbivorous marine species. However, the restricted group of food-related compounds perceived by this species as incitants or suppressants and as stimulants or deterrents was shown to be remarkably related to other vertebrates whose kinship was confirmed by the sequencing of the genome of another plant-eater sea urchin.

Trophic niches reflect compositional differences in microbiota among Caribbean sea urchins.

Sea urchins play a critical role in marine ecosystems, as they actively participate in maintaining the balance between coral and algae. We performed the first in-depth survey of the microbiota associated with four free-living populations of Caribbean sea urchins: Lytechinus variegatus, Echinometra lucunter, Tripneustes ventricosus, and Diadema antillarum. We compared the influence of the collection site, echinoid species and trophic niche to the composition of the microbiota. This dataset provides a comprehensive overview to date, of the bacterial communities and their ecological relevance associated with sea urchins in their natural environments. A total of sixty-samples, including surrounding reef water and seagrass leaves underwent 16S rRNA gene sequencing (V4 region) and high-quality reads were analyzed with standard bioinformatic approaches. While water and seagrass were dominated by Cyanobacteria such as Prochlorococcus and Rivularia respectively, echinoid gut samples had dominant Bacteroidetes, Proteobacteria and Fusobacteria. Propionigenium was dominant across all species’ guts, revealing a host-associated composition likely responsive to the digestive process of the animals. Beta-diversity analyses showed significant differences in community composition among the three collection sites, animal species, and trophic niches. Alpha diversity was significantly higher among L. variegatus samples compared to the other species. L. variegatus also displayed an increased abundance of Planctomycetes and Cyanobacterial OTUs. The bacterial community of this herbivorous echinoid reflected similarities to the microfilm community found on Thalassia testudinum leaves; a very abundant seagrass and its main food resource. The results of this study elaborate on the microbial ecology of four important Caribbean echinoids, confirming that selection on the microbial community is trophic-niche dependent.