Asteroid Species Research Articles

A mass spectrometry database for the identification of marine animal saponin-related metabolites.

Saponins encompass a diverse group of naturally occurring glycoside molecules exhibiting amphiphilic properties and a broad range of biological activities. There is a resurgence of interest in those saponins produced by marine organisms based on their potential therapeutic benefits, application in food products and most recently their potential involvement in intra- and inter-species chemical communication. The continual advancements in liquid chromatography techniques and mass spectrometry technologies have allowed for greater detection rates, as well as improved isolation and elucidation of saponins. These factors have significantly contributed to the expansion in the catalogue of known saponin structures isolated from marine invertebrates; however, there currently exists no specific chemical library resource to accelerate the discovery process. In this study, a Marine Animal Saponin Database (MASD v1.0) has been developed to serve as a valuable chemical repository for known marine saponin-related data, including chemical formula, molecular mass and biological origin of nearly 1000 secondary metabolites associated with saponins produced by marine invertebrates. We demonstrate its application with an exemplar asteroid extract (Acanthaster cf. solaris, also known as crown-of-thorns starfish; COTS), identifying saponins from the MASD v1.0 that have been previously reported from COTS, as well as 21 saponins isolated from multiple other related asteroid species. This database will help facilitate future research endeavours, aiding researchers in exploring the vast chemical diversity of saponins produced by marine organisms and providing ecological insights, and the realisation of their potential for various applications, including as pharmaceuticals.

Complete Mitochondrial Genomes and Phylogenetic Analysis of Genus Henricia (Asteroidea: Spinulosida: Echinasteridae).

The genus Henricia is known to have intraspecific morphological variations, making species identification difficult. Therefore, molecular phylogeny analysis based on genetic characteristics is valuable for species identification. We present complete mitochondrial genomic sequences of Henricia longispina aleutica, H. reniossa, and H. sanguinolenta for the first time in this study. This study will make a significant contribution to our understanding of Henricia species and its relationships within the class Asteroidea. Lengths of mitochondrial genomes of the three species are 16,217, 16,223, and 16,194 bp, respectively, with a circular form. These genomes contained 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a D-loop. The gene order and direction aligned with other asteroid species. Phylogenetic relationship analysis showed that our Henricia species were in a monophyletic clade with other Henricia species and in a large clade with species (Echinaster brasiliensis) from the same family. These findings provide valuable insight into understanding the phylogenetic relationships of species in the genus Henricia.

Preliminary study of the population and reproductive dynamics of Echinaster sepositus (Spinulosida: Echinasteridae) in Cala del Racó

Introduction: The red starfish (Echinaster sepositus) is one of the most common asteroid species in the Mediterranean Sea. However, information about their biology or their role in benthic communities is scarce.
 Objective: This study aims to provide new information on the ecology of this species through the temporal characterization of the population of E. sepositus in Cala del Racó (Alicante, Spain) and the in situ monitoring of its reproductive cycle.
 Methods: For this purpose, three study areas were established at different depths. For each of the recorded starfish, data about the size, the substrate on which it was found, the area, the depth and the sex in the case of observing the reproduction were collected.
 Results: A total of 19 samplings have been carried out throughout a year of study. In this way, it has been possible to observe that the density of individuals increases in the shallower zone during autumn and winter, when the temperature drops to 14.13 ºC, while it decreases in spring and summer when the temperature rises to 27.17 ºC. Those results are reversed in the deepest part of the study. The highest density of individuals (0.51 ind/m2) occurred in October. Arborescent photophilic algae and crustose coralline algae were the substrates with the highest number of E. sepositus recorded. Medium to large specimens are located preferably on crustose coralline algae or arborescent photophilic algae, while smaller individuals were mostly located on Posidonia oceanica. No specimens of E. sepositus were observed spawning.
 Conclusions: Data leads to assume that there is a migration of starfishes towards more superficial areas when the water is at colder temperature and towards deeper areas when the temperature increases. It is valued the possibility that there is a change in the nutritional needs of E. sepositus throughout its development. According to our observations, the future reproduction studies should be concentrated between late-summer and early-autumn.

Insights into the diversification of deep-sea endoparasites: Phylogenetic relationships within Dendrogaster (Crustacea: Ascothoracida) and a new species description from a western Pacific seamount

Parasitic crustacean Dendrogaster is completely endoparasitic and is not known from any marine invertebrates other than asteroids. Understanding the diversity of this group is considerably lagging, as it is an internal parasite that is not easily detected without dissecting the host. The group is thought to have coevolved with asteroids due to its endoparasitism; however, this has not been verified due to a lack of phylogenetic studies. A molecular phylogenetic analysis was required to understand the evolution of this very specialized genus. During a biodiversity survey at An'ei Seamount established as an offshore marine protected area in Japan, we discovered an unknown species of Dendrogaster inside a recently described species of asteroids. In this study, we attempted to elucidate the phylogenetic relationships of multiple species of Dendrogaster, including a new species, Dendrogaster nike sp. nov., collected from the An'ei Seamount of the Nishi-Shichito Ridge. We determined the COI and 18S gene sequences of some Dendrogaster species and reconstructed a phylogenetic tree. Upon plotting the information of the host and habitat depth onto the phylogenetic tree, evidence of coevolution between Dendrogaster and its host, which is commonly observed in endosymbiotic organisms, was not observed. Instead, our findings suggest that species diversification in Dendrogaster may have occurred based on habitat depth rather than coevolution with the host.

Is It in the Stars? Exploring the Relationships between Species' Traits and Sea Star Wasting Disease.

AbstractAn explanation for variation in impacts of sea star wasting disease across asteroid species remains elusive. Although various traits have been suggested to play a potential role in sea star wasting susceptibility, currently we lack a thorough comparison that explores how life-history and natural history traits shape responses to mass mortality across diverse asteroid taxa. To explore how asteroid traits may relate to sea star wasting, using available data and recognizing the potential for biological correlations to be driven by phylogeny, we generated a supertree, tested traits for phylogenetic association, and evaluated associations between traits and sea star wasting impact. Our analyses show no evidence for a phylogenetic association with sea star wasting impact, but there does appear to be phylogenetic association for a subset of asteroid life-history traits, including diet, substrate, and reproductive season. We found no relationship between sea star wasting and developmental mode, diet, pelagic larval duration, or substrate but did find a relationship with minimum depth, reproductive season, and rugosity (or surface complexity). Species with the greatest sea star wasting impacts tend to have shallower minimum depth distributions, they tend to have their median reproductive period 1.5 months earlier, and they tend to have higher rugosities relative to species less affected by sea star wasting. Fully understanding sea star wasting remains challenging, in part because dramatic gaps still exist in our understanding of the basic biology and phylogeny of asteroids. Future studies would benefit from a more robust phylogenetic understanding of sea stars, as well as leveraging intra- and interspecific comparative transcriptomics and genomics to elucidate the molecular pathways responding to sea star wasting.

Species composition of sea stars (Echinodermata: Asteroidea) in the Patagonian Argentinian deep sea, including seven new records: connectivity with sub-Antarctic and Antarctic fauna

The main target of this paper is to improve the knowledge of the species composition of sea stars in Patagonian Argentine deep sea reaching depths of 2062 m. In addition, these results offer us the opportunity to analyze the possible connections between Argentinian marine fauna and adjacent Antarctic areas that have become a topic of interest in the past few years. This work is based on Atlantic Projects’ surveys carried out on an atypical and especially vulnerable marine ecosystems (canyons created from craters collapse by gas leaks). These are profusely impacted by frequent fishing activities, being one of the most important and international fishing grounds, where 887 records (1878 specimens) of 41 species of asteroids were collected in 217 stations ranging from 219 to 2062 m in depth. Seven of those species are proposed as new records: (Diplasterias octoradiata (Studer 1885), Plutonaster bifrons (Wyville Thomson, 1873), Radiaster elegans Perrier, 1881, Anseropoda antarctica Fisher, 1940, Pillsburiaster calvus Mah, 2011, Paralophaster lorioli (Koehler, 1907), Pteraster flabellifer Mortensen 1933). After refining the database built from literature and open-access databases such as OBIS and AntBIF, the new Argentinian asteroids deep-water checklist contains 2198 records from 64 asteroids species including the 7 new records proposed. Most of these 64 species (89.06%) are present in Antarctic-adjacent waters, and after the study of their occurrences at traditional biogeographic entities, our results support the hypothesis that Argentinian waters (in the case of the class Asteroidea) should be considered part of the sub-Antarctic entity.

The asteroid species of Lamarck (Echinodermata: Asteroidea)

Zoologist Peron and artist Lesueur, both members of the scientific staff of the Baudin expedition to the Southern Lands (September 1800-March 1804), collected during their voyage 36 different species of asteroids. This is what wrote Lamarck in a report made in June 1804. This number was clearly reduced by Lamarck himself who, in his 1816 publication, listed only 15 species from the South Seas in the Paris Museum collection. However, the different asteroids collected during the expedition were drawn by Lesueur (water colours and pencil drawings) who thus realised a real pictorial register. Lesueur's drawings are housed in the Le Havre Museum. Due to their realism and precision, the drawings make it easy to identify the species. Confrontation of Lamarck's report (1804) and publication (1816) with Lesueur's drawings (done between 1802 and 1804) gives a new, more precise idea of the importance of the collection of South Seas asteroids brought back to France and allows to reliably count the number of new species that it contained. Also, this makes it possible to complete the often too brief descriptions of some Lamarckian species and to clarify their status. Eleven taxonomic changes are thus proposed here: Asterias calcar var. quinqueangula is synonymized with Parvulastra exigua (Lamarck, 1816), Asterias calcitrapa var. 1 with Bollonaster pectinatus (Sladen, 1883), Asterias calcitrapa var. 2 with Astropecten vappaMuller & Troschel, 1843, Asterias nodosa var. 3 with Protoreaster lincki (Blainville, 1830), Asterias pentagonula with Tosia australisGray, 1840, Asterias pleyadella with Protoreaster sp., Asterias punctata with Asteropsis carinifera (Lamarck, 1816), Asterias rosacea var. lobis senis with Anseropoda sp., Asteriscus setaceus with Paranepanthia grandis (H. L. Clark, 1928), Astrogonium lamarckiiMuller & Troschel, 1842 with Goniaster tessellatus (Lamarck, 1816) and Asterias cuspidata is moved to the genus Mediaster Stimpson, 1857 as Mediaster cuspidatus (Lamarck, 1816) n. comb.

Surveillance of densoviruses and mesomycetozoans inhabiting grossly normal tissues of three Aotearoa New Zealand asteroid species.

Asteroid wasting events and mass mortality have occurred for over a century. We currently lack a fundamental understanding of the microbial ecology of asteroid disease, with disease investigations hindered by sparse information about the microorganisms associated with grossly normal specimens. We surveilled viruses and protists associated with grossly normal specimens of three asteroid species (Patiriella regularis, Stichaster australis, Coscinasterias muricata) on the North Island / Te Ika-a-Māui, Aotearoa New Zealand, using metagenomes prepared from virus and ribosome-sized material. We discovered several densovirus-like genome fragments in our RNA and DNA metagenomic libraries. Subsequent survey of their prevalence within populations by quantitative PCR (qPCR) demonstrated their occurrence in only a few (13%) specimens (n = 36). Survey of large and small subunit rRNAs in metagenomes revealed the presence of a mesomycete (most closely matching Ichthyosporea sp.). Survey of large subunit prevalence and load by qPCR revealed that it is widely detectable (80%) and present predominately in body wall tissues across all 3 species of asteroid. Our results raise interesting questions about the roles of these microbiome constituents in host ecology and pathogenesis under changing ocean conditions.

Morphology of endoskeleton and spination in the sea star Midgardia xandaros (Brisingida: Brisingidae) from the Gulf of Mexico

Introduction. The deep-sea asteroid species of Brisingida have a nearly global distribution but have remained poorly understood due to their deep bathymetric distributions and fragile skeletons. Objective. To describe the external and internal morphology of Midgardia xandaros including the skeletal arrangement, through multifocal and SEM techniques. Methods. We examined a total of 21 specimens, including 27 arm fragments, from the Gulf of Mexico and Honduras. Two specimens were dissected. Results. Detailed descriptions of pedicellariae, abactinal, intercostal, inferomarginal, adambulacral, ambulacral, odontophore, and oral ossicles, and their spines are provided, emphasizing the articulations and muscle attachments. C-shaped valves pedicellariae and small pedicellariae valves with shorter denticulation areas were recognized. Conclusions. The morphological description of M. xandaros is expanded, providing the most extensive description of abactinal, first adambulacral, first and subsequent inferomarginal ossicles, abactinal spines, and C-shaped, crossed pedicellariae, as well as the distal arm plates, for a brisingid species using SEM to date.

Evidence That Microorganisms at the Animal-Water Interface Drive Sea Star Wasting Disease.

Sea star wasting (SSW) disease describes a condition affecting asteroids that resulted in significant Northeastern Pacific population decline following a mass mortality event in 2013. The etiology of SSW is unresolved. We hypothesized that SSW is a sequela of microbial organic matter remineralization near respiratory surfaces, one consequence of which may be limited O2 availability at the animal-water interface. Microbial assemblages inhabiting tissues and at the asteroid-water interface bore signatures of copiotroph proliferation before SSW onset, followed by the appearance of putatively facultative and strictly anaerobic taxa at the time of lesion genesis and as animals died. SSW lesions were induced in Pisaster ochraceus by enrichment with a variety of organic matter (OM) sources. These results together illustrate that depleted O2 conditions at the animal-water interface may be established by heterotrophic microbial activity in response to organic matter loading. SSW was also induced by modestly (∼39%) depleted O2 conditions in aquaria, suggesting that small perturbations in dissolved O2 may exacerbate the condition. SSW susceptibility between species was significantly and positively correlated with surface rugosity, a key determinant of diffusive boundary layer thickness. Tissues of SSW-affected individuals collected in 2013–2014 bore δ15N signatures reflecting anaerobic processes, which suggests that this phenomenon may have affected asteroids during mass mortality at the time. The impacts of enhanced microbial activity and subsequent O2 diffusion limitation may be more pronounced under higher temperatures due to lower O2 solubility, in more rugose asteroid species due to restricted hydrodynamic flow, and in larger specimens due to their lower surface area to volume ratios which affects diffusive respiratory potential.

New asteroid species from the Eocene of Seymour Island, Antarctica

Palopolo, Evangelina. Universidad Nacional de Rio Negro. Instituto de Investigacion en Paleobiologia y Geologia. Rio Negro, Argentina.

Oceanographic conditions and diversity of sea stars (Echinodermata: Asteroidea) in the Gulf of California, México.

Species richness is one of the best indicators of biodiversity. However, there are few investigations on concordance of diversity patterns and environmental settings for marine regions. The objectives of this study were to correlate species richness of shallow water (< 200 m deep) sea stars with key oceanographic factors in the Gulf of California, México, and to predict species richness of Asteroidea using multiple regressions. In these analyses the Gulf was divided into nine sections of one degree in latitude (from 23-31 degrees N), at each section we recorded: continental shelf area (at 100 and 200 m depth), temperature mean and range at three depth levels (0, 60 and 120 m), thermocline depth, surface nutrient concentrations (nitrates, phosphates and silicates), surface photosynthetic pigment concentration, and integrated productivity. Sea star species richness at each latitudinal section was estimated from literature data, new collections and museum records. Species were assigned to one of the following feeding guilds: predators of small mobile invertebrates (I), detritivores (D), predators of colonial organisms (C), generalist carnivores (G), and planktivores (P). There are 47 shallow water asteroid species in the Gulf of California (16 I, 15 D, eight C, six G, one P and one not assigned). Total species richness and guild species richness showed strong latitudinal attenuation patterns and were higher in the southernmost Gulf, an area characterized by a narrow shelf, high temperature, and low nutrient concentrations. Species diversity for each guild was correlated to a set of oceanographic parameters: temperature, nitrate concentration, and integrated productivity were linked to richness in must cases. We detected that nutrients and surface pigments always presented negative relationships with species richness, indicating that productive environments limit asteroid diversity in the study area. Finally, the postulated regression models to estimate species richness from oceanographic data were significant and highly precise. We conclude that species richness of Asteroidea in the Gulf of California is related to oceanographic conditions and can be estimated from regional oceanographic information.

Lipid and protein utilization during lecithotrophic development in the asteroid Stegnaster inflatus, with a review of larval provisioning in lecithotrophic echinoderms

The eggs of echinoderms with lecithotrophic development provide structural and nutritional materials (lipids, proteins) to complete development without any external sources of nutrition. Previous studies have suggested that a relatively large proportion of the maternal lipid reserves remain after settlement to provision the early post-metamorphic juvenile. Here we examined lipid and protein utilization during lecithotrophic development of the asterinid starfish Stegnaster inflatus which has large (~400 µm diameter), negatively buoyant eggs. S. inflatus produces eggs with a large amount of lipid (mean ± SD: 2047 ± 315 ng egg-1), with 26% structural lipids and 74% energetic lipids dominated by diacylglycerol ether (DAGE; 66%). Similar amounts of protein were present in the egg (mean ± SD: 2143 ± 157 ng egg-1), with a lipid:protein ratio of 0.96. Approximately 80% of the egg protein is used prior to settlement. In contrast, 51.0% of the energetic lipids provided in the egg, and 40.3% of the DAGE remain for provisioning of the early juvenile. A review of lecithotrophic development in echinoderms reveals that asteroid, echinoid and ophiuroid species have an excess of 50% of the maternal lipids remaining in the settled post-larva. When considering maternal investment in offspring for lecithotrophic developers, we need to consider energetic use during the short dispersal period, as well as provisioning for post-metamorphic early juvenile life.

Coelomic Fluid Evaluation in Pisaster ochraceus Affected by Sea Star Wasting Syndrome: Evidence of Osmodysregulation, Calcium Homeostasis Derangement, and Coelomocyte Responses.

Sea Star Wasting Syndrome (SSWS) is one of the largest marine wildlife die-offs ever recorded, killing millions of sea stars from more than 20 Asteroid species from Alaska to Mexico from 2013 to 2015 from yet undetermined cause(s). Coelomic fluid surrounds the sea star's organs, playing critical roles in numerous systemic processes, including nutrient transportation and immune functions. Coelomocytes, which are cellular components of coelomic fluid and considered functionally equivalent to vertebrate leukocytes, are responsible for innate cell-mediated immunity. The objectives of this study were to (1) evaluate changes in coelomic fluid chemistry, coelomocyte counts, and cytology from ochre sea stars (Pisaster ochraceus) (n = 55) with clinical signs consistent with SSWS at varying intensity (SSWS score 1: n = 4, score 2: n = 2, score 3: n = 3, score 4: n = 18, score 5: n = 26) in comparison to coelomic fluid from clinically normal sea stars (n = 26) and to (2) correlate SSWS score with cellular and biochemical analytes. SSWS-affected sea stars had wider ranges of all electrolytes, except calcium; statistically significantly higher chloride, osmolality, and total protein; lower calcium; and higher coelomocyte counts when compared to clinically normal sea stars maintained under identical environmental conditions. Free and/or phagocytized bacteria were noted in 29% (16 of 55) coelomic fluid samples from SSWS-affected sea stars but were absent in clinically normal sea stars. SSWS score correlated significantly with increasing chloride concentration, osmolality, and coelomocyte counts. These chemistry and cytological findings in coelomic fluid of SSWS-affected sea stars provide insight into the pathophysiology of SSWS as these results suggest osmo- and calcium dysregulation, coelomocyte responses, and presumptive opportunistic bacterial infection in SSWS-affected sea stars. This information provides potential future research applications for the development of treatment strategies for sea stars in managed care and for understanding the complexity of various biochemical and cellular pathophysiological mechanisms involved in sea star wasting.

Echinoderm functional diversity does not correlate with the protection level of marine protected areas in the Mexican Pacific

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

Sea star wasting disease demography and etiology in the brooding sea star Leptasterias spp.

Sea star wasting disease (SSWD) describes a suite of disease signs believed to have led to catastrophic die-offs in many asteroid species, beginning in 2013. While most studies have focused on large, easily visible sea stars with widely-dispersing larvae, less information is available on the effect of this disease outbreak on smaller sea star species, such as the six-armed sea star Leptasterias spp. Unlike many larger sea stars, Leptasterias brood non-feeding young instead of broadcast-spawning planktonic larvae. Limited dispersal and thus limited gene flow may make these sea stars more vulnerable to local selective pressures, such as disease outbreaks. Here, we examined Leptasterias populations at sites along the California coast and documented abundance changes coincident with recent Pacific coast SSWD in 2014. Detection of Leptasterias in central California declined, and Leptasterias were not detected at multiple sites clustered around the San Francisco Bay outflow in the most recent surveys. Additionally, we categorized disease signs in Leptasterias in the field and laboratory, which mirrored those seen in larger sea stars in both settings. Finally, we found that magnesium chloride (MgCl2) slowed the progression of physical deterioration related to SSWD when applied to sea stars in the laboratory, suggesting that MgCl2 may prolong the survival of diseased individuals.

New articulated asteroids (Echinodermata, Asteroidea) and ophiuroids (Echinodermata, Ophiuroidea) from the Late Jurassic (Volgian / Tithonian) of central Spitsbergen

The Late Jurassic–Early Cretaceous Slottsmøya Member of the Agardhfjellet Formation in central Spitsbergen has yielded two new species of asteroids and two species of ophiuroids, one of which is described as new. Polarasterias janusensis Rousseau &amp; Gale gen. et sp. nov. is a forcipulatid neoasteroid with elongated arms, small disc and very broad ambulacral grooves with narrow adambulacrals. Savignaster septemtrionalis Rousseau &amp; Gale sp. nov. is a pterasterid with well-developed interradial chevrons. The Spitsbergen specimens are the first described articulated material of Savignaster and reveal the overall arrangement of the ambulacral groove ossicles. Ophiogaleus sp. is an ophiacanthid with relatively long jaws and lateral arm plates, with a coarsely reticulate outer surface. Here again, we report the first articulated skeletons of this genus, providing unprecedented insights into the disc morphology. Ophioculina hoybergia Rousseau &amp; Thuy gen. et sp. nov. is an ophiopyrgid with a well-developed arm comb and tentacle pores reduced to within-plate perforations starting at median arm segments. These new finds are important additions to the asterozoan fossil record with regard to their good degree of articulation and the high latitudinal position of the localities. They significantly add to the set of exhaustively known fossil asterozoan taxa which play a key role in the phylogenetic analysis and reconstruction of evolutionary history.

Investigating the Complex Association Between Viral Ecology, Environment, and Northeast Pacific Sea Star Wasting

Sea Star Wasting Disease (SSWD) describes a suite of disease signs that affected > 20 species of asteroid since 2013 along a broad geographic range from the Alaska Peninsula to Baja California. Previous work identified the Sea Star associated Densovirus (SSaDV) as the best candidate pathogen for SSWD in 3 species of common asteroid (Pycnopodia helianthoides, Pisaster ochraceus and Evasterias troscheli), and virus-sized material (<0.22 µm) elicited SSWD signs in P. helianthoides. However, the ability of virus-sized material to elicit SSWD in other species of asteroids was not known. Discordance between detection of SSaDV by qPCR and by viral metagenomics inspired the redesign of qPCR primers to encompass SSaDV and two densoviral genotypes detected in wasting asteroids. Analysis of asteroid samples collected during SSWD emergence in 2013-2014 showed an association between wasting asteroid-associated densoviruses (WAaDs) and SSWD in only one species (P. helianthoides). WAaDs were found in association with asymptomatic asteroids in contemporary (2016 and later) populations, suggesting that they form subclinical infections at the times they were sampled. WAaDs were found in SSWD-affected P. helianthoides after being absent in asymptomatic individuals a year earlier at one location (Kodiak). Direct challenge of P. ochraceus, Pisaster brevispinus and E. troscheli with virus-sized material from SSWD-affected individuals did not elicit SSWD in any trial. RNA viral genomes discovered in viral metagenomes and host transcriptomes had viral loads and metagenome fragment recruitment patterns that were inconsistent with SSWD. Analysis of water temperature and precipitation patterns on a regional scale suggests that SSWD occurred following dry conditions at several locations, but mostly was inconsistently associated with either parameter. Semi-continuous monitoring of SSWD subtidally at two sites in the Salish Sea from 2013-2017 indicated that SSWD in E. troscheli and P. ochraceus was associated with elevated water temperatures, but wasting in P. helianthoides occurred irrespective of environmental conditions. Our data therefore do not support that widespread SSWD in species other than P. helianthoides is associated with potential viral pathogens. Rather, we speculate that SSWD may represent a syndrome of heterogeneous etiologies between geographic locations, between species, or even within a species between locations.

Species identification of echinoderms from the North Sea by combining morphology and molecular data

BackgroundTaxonomic uncertainties in the morphological species identification and taxonomic revisions in individual groups are known for all echinoderm classes. These uncertainties in morphological species identification and discrimination have spawned the application of molecular genetic identification techniques. However, as the fundamental step to allow and ensure future molecular species identification, valid and comprehensive reference library entries comprising morphological and molecular species information together with various metadata are essentially needed. In our study we compare morphological and molecular genetic species identification techniques for representatives of North Sea echinoderm classes, i.e. the Asteroidea, Ophiuroidea, Echinoidea and Holothuroidea.MethodsIndividuals were sampled during different surveys in different regions of the North Sea, identified to species level based on morphological diagnostic features, and were genetically analysed using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI).Results and DiscussionThe morphological determination revealed 32 species including one taxon determined only to genus level. In contrast to this, the COI analysis supported 34 monophyletic clades with pronounced differences between the intra- and the inter-specific genetic variability (a barcoding gap of 4.93 %) with highest intra-specific variabilities found in the ophiuroid species Amphiura filiformis, A. chiajei and Ophiura sarsii. In 94 % of the investigated species, morphological identification and COI sequence clusters were congruent whereas for two asteroid species we found an underestimated diversity. For Astropecten irregularis, one of the most common starfish species of the North Sea, we found two distinct and possibly depth-related clades, probably sibling species, differing by 11.1–11.9 % sequence divergences (p-distances). For two starfish individuals, morphologically identified as Henricia sanguinolenta, the COI analysis revealed two monophyletic clades, of which one was classified as H. cf. oculata by comparison to published sequences.ConclusionsThis newly established sequence reference library for the North Sea Echinodermata allows and ensures future molecular species identification for various life-cycle stages including juveniles and meroplanktonic larvae and provides sequences for phylogeographic studies and the detection of sibling as well as cryptic species.

Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids.

Sea star wasting disease devastated intertidal sea star populations from Mexico to Alaska between 2013–15, but little detail is known about its impacts to subtidal species. We assessed the impacts of sea star wasting disease in the Salish Sea, a Canadian / United States transboundary marine ecosystem, and world-wide hotspot for temperate asteroid species diversity with a high degree of endemism. We analyzed roving diver survey data for the three most common subtidal sea star species collected by trained volunteer scuba divers between 2006–15 in 5 basins and on the outer coast of Washington, as well as scientific strip transect data for 11 common subtidal asteroid taxa collected by scientific divers in the San Juan Islands during the spring/summer of 2014 and 2015. Our findings highlight differential susceptibility and impact of sea star wasting disease among asteroid species populations and lack of differences between basins or on Washington’s outer coast. Specifically, severe depletion of sunflower sea stars (Pycnopodia helianthoides) in the Salish Sea support reports of major declines in this species from California to Alaska, raising concern for the conservation of this ecologically important subtidal predator.