Brittle Star Species Research Articles

Adverse effects of crushed seafloor massive sulphide deposits on the boreal deep-sea sponge Geodia barretti Bowerbank, 1858 and its associated fauna

Abundant mineral resources in the deep sea are prospected for mining for the global metal market. Seafloor massive sulphide (SMS) deposits along the Mid-Atlantic Ridge are one of the potential sources for these metals. The extraction of SMS deposits will expose adjacent marine ecosystems to suspended particle plumes charged with elevated concentrations of heavy metals and other potentially toxic compounds. Up to date there is no information about the impact of mining activities on deep-sea benthic ecosystems such as abundant deep-sea sponge grounds in the North Atlantic Ocean. Sponge grounds play a major role in benthic-pelagic coupling and represent an important habitat for a diversity of vertebrates, invertebrates and microorganisms. To simulate the effects of mining plumes on benthic life in the deep sea, we exposed Geodia barretti, a dominant sponge species in the North Atlantic Ocean, and an associated brittle star species from the genus Ophiura spp. to a field-relevant concentration of 30 mg L−1 suspended particles of crushed SMS deposits. Three weeks of exposure to suspended particles of crushed SMS resulted in a tenfold higher rate of tissue necrosis in sponges. All brittle stars in the experiment perished within ten days of exposure. SMS particles were evidently accumulated in the sponge's mesohyl and concentrations of iron and copper were 10 times elevated in SMS exposed individuals. Oxygen consumption and clearance rates were significantly retarded after the exposure to SMS particles, hampering the physiological performance of G. barretti. These adverse effects of crushed SMS deposits on G. barretti and its associated brittle star species potentially cascade in disruptions of benthic-pelagic coupling processes in the deep sea. More elaborate studies are advisable to identify threshold levels, management concepts and mitigation measures to minimize the impact of deep-sea mining plumes on benthic life.

An eDNA metabarcoding of brittle stars: Examples from the Seto Inland Sea, a semi-closed marine area

Marine ecosystem are facing a crisis due to climate change and anthropogenic activities, and many marine organisms are threatened by declining biodiversity. Regular and extensive surveys of these organisms are necessary to conserve the biodiversity. Conventional methods, however, rely on direct observation and collection of specimens by experts with identification and sampling skills. Using environmental DNA (eDNA) metabarcoding methods, we detected a total of 15 brittle star species at two sites in the Seto Inland Sea, a semi-enclosed marine area in Japan. This study showed that brittle stars are useful environmental indicator organisms, and that the eDNA metabarcoding method specific to brittle star is expected to be a useful tool for a wide-ranging and simple investigation method for marine ecosystems. Further investigations will need to verify whether species detected by metabarcoding without being confirmed by direct observations are due to false positives and whether this is due to the semi-enclosed character of the area.

Spiky fossil unveiled as oldest southern hemisphere brittle star species

Spiky fossil unveiled as oldest southern hemisphere brittle star species

Spiky fossil unveiled as oldest southern hemisphere brittle star species

Spiky fossil unveiled as oldest southern hemisphere brittle star species

Deepest known novel species of the genus Ophiuroglypha Hertz, 1927 (Echinodermata: Ophiuroidea) from the central rift zone, Philippine Sea

A new species of brittle star was collected in 2021 by the manned submersible “Fendouzhe” from the central rift zone deep waters, Philippine Sea, at a depth of 7729 m. It is described as Ophiuroglypha fendouzhe sp. nov., and is distinguished from its congeners based on the following features: slender arms, separated dorsal and ventral arm plates, overlapping large disc scales, and distally contiguous radial shields. We provide comprehensive descriptions of the external morphological features, including characteristics of the arm skeleton, and a phylogenetic analysis based on COI sequences. The interspecific genetic distance variation in the genus Ophiuroglypha found in this study was 3.89% to 24.25%. The new species constitutes the deepest known record for the genus Ophiuroglypha.

Growth in two deep-sea associates: the octocoral Pseudogorgia bellona and the euryalid snake star Asteroschema ajax.

The deep-sea octocoral Pseudochrysogorgia bellona was recently described from specimens sampled on the Chesterfield Plateau, off New Caledonia. It is morphologically and genetically similar to the con-familial Metallogorgia melanotrichos, which is known to closely associate with a species of brittle star, Ophiocreas oedipus. These latter two species have never been observed separately and are thought to grow synchronously. The morphological similarity between M. melanotrichos and P. bellona makes the latter another possible host for ophiuroids. However, no brittle star was associated with P. bellona specimens from the type collection. In 2017, 130 P. bellona colonies were sampled near the type locality, and 98% were associated with Asteroschema ajax, a species closely related to O. oedipus. Mitochondrial DNA analysis confirmed the morphological identifications of both P. bellona and A. ajax. Uni- and multivariate statistical analyses were used to characterize the morphological space of both species to test if larger ophiuroids are associated with larger corals. Two variables were measured to estimate the size of the coral (total height and diameter of the skeletal axis at its base) and 9 variables were used to characterize the brittle star (disc and arm morphology). Morphological variables representing the size for both species were significantly correlated (Spearman rank correlation coefficient: 50%, p < 0.001), suggesting that larger ophiuroids indeed associate with larger corals. This is one of the rare studies that allowed comparison of growth in associated deep-sea invertebrates.

Biomass of Ophiuroidea и Echinarachnius parma on a plot of the West Kamchatka shelf in 2013–2017

According to the results of bottom grab surveys carried out in 2013–2016, data on the biomass (g/m2) of the dominant sea urchin species Echinarachnius parma and the complex of brittle stars on a plot of the West Kamchatka shelf are given. The average biomass of Echinarachnius parma for the surveyed plot varied over the years and in 2013 was 45.298 ± 25.582 g/m2, in 2014 – 48.784 ± 26.561 g/m2, in 2015 – 19.557 ± 11.678 g/m2, in 2016 – 18.957 ± 13.192 g/m2. In terms of biomass on the surveyed plot (g/m2) the main role among the echinoderms belongs to fl at sand dollars, and in terms of population density (ind./m2) – to brittle stars. 11 species of brittle stars from 4 families were noted. In terms of population density the most common species among the brittle stars are Amphiodia craterodmeta and Ophiura quadrispina.

Climate warming erodes tropical reef habitat through frequency and intensity of episodic hypoxia

Climate warming threatens marine life by increasing metabolic oxygen demand while decreasing oxygen availability. Tropical species living in warm, low oxygen environments may be most at risk, but their tolerances and exposures to these stressors remain poorly documented. We evaluated habitat restrictions for two brittle star species from Caribbean coral reefs by integrating field observations, laboratory experiments and an ecophysiological model. The absence of one species from the warmest reefs results from vital activity restrictions during episodic low oxygen extremes, even though average conditions are well within physiological tolerance limits. Over the past decade, warmer temperatures have been significantly correlated with a greater frequency and intensity of hypoxic events. Continued warming will progressively exclude hypoxia-tolerant species, even if average oxygen remains constant. A warming-driven increase in frequency or intensity of low oxygen extremes could similarly accelerate habitat loss across other marine ecosystems.

Development of two new sets of PCR primers for eDNA metabarcoding of brittle stars (Echinodermata, Ophiuroidea)

Brittle stars (class Ophiuroidea) are marine invertebrates comprising approximately 2,100 extant species, and are considered to constitute the most diverse taxon of the phylum Echinodermata. As a non-invasive method for monitoring biodiversity, we developed two new sets of PCR primers for metabarcoding environmental DNA (eDNA) from brittle stars. The new primer sets were designed to amplify 2 short regions of the mitochondrial 16S rRNA gene, comprising a conserved region (111–115 bp, 112 bp on average; named “16SOph1”) and a hyper-variable region (180–195 bp, 185 bp on average; named “16SOph2”) displaying interspecific variation. The performance of the primers was tested using eDNA obtained from two sources: a) rearing water of an 2.5 or 170 L aquarium tanks containing 15 brittle star species and b) from natural seawater collected around Misaki, the Pacific coast of central Japan, at depths ranging from shallow (2 m) to deep (&amp;gt; 200 m) sea. To build a reference library, we obtained 16S rRNA sequences of brittle star specimens collected from around Misaki and from similar depths in Japan, and sequences registered in International Nucleotide Sequence Database Collaboration. As a result of comparison of the obtained eDNA sequences with the reference library 37 (including cryptic species) and 26 brittle star species were detected with certain identities by 16SOph1 and 16SOph2 analyses, respectively. In shallow water, the number of species and reads other than the brittle stars detected with 16SOph1 was less than 10% of the total number. On the other hand, the number of brittle star species and reads detected with 16SOph2 was less than half of the total number, and the number of detected non-brittle star metazoan species ranged from 20 to 46 species across 6 to 8 phyla (only the reads at the “Tank” were less than 0.001%). The number of non-brittle star species and reads at 80 m was less than 10% with both of the primer sets. These findings suggest that 16SOph1 is specific to the brittle star and 16SOph2 is suitable for a variety of marine metazoans. It appears, however, that further optimization of primer sequences would still be necessary to avoid possible PCR dropouts from eDNA extracts. Moreover, a detailed elucidation of the brittle star fauna in the examined area, and the accurate identification of brittle star species in the current DNA databank is required.

Spatial models of suitable sandy substrates for brittle star community conservation in Sancang Coast, West Java, Indonesia

Abstract. Suprapto PK, Husna IR, Meylani V, Basukriadi A, Wibowo AA, Nurdin E. 2022. Spatial models of suitable sandy substrates for brittle star community conservation in Sancang Coast, West Java, Indonesia. Indo Pac J Ocean Life 6: 87-93. The brittle star is known as one of the echinoids with the largest members. Currently, brittle star species are threatened due to harvests for fulfilling decorative species demands in aquariums. This study aims to determine suitable sandy substrates for the brittle star community in Sancang Coast, West Java, Indonesia, in three representative stations. Brittle star presences and environmental variables were surveyed using belt transect methods, and sandy substrate suitability was determined using scoring and an interpolation method aided by GIS. Results show three species belong to the Ophiocomidae, with Ophiocoma scolopendrina (Lamarck, 1816) (brittle lagoon star) being the most abundant. About 394,631 m2 of sandy substrates were available, and an estimated 47.52% is considered very suitable for brittle stars. Most suitable sandy substrates were located on the West side, characterized by low water temperature, high salinity, and alkaline water. In contrast, less suitable sandy substrates were located on the coast's east side, characterized by high water temperature, low salinity, and acidic water. To conclude, this research has identified which parts of the Sancang Coast should be prioritized to conserve brittle stars.

Strategy of micro-environmental adaptation to cold seep among different brittle stars’ colonization

Diffusing fluid from methane seepage in cold seep field creates zones with physicochemical gradients and divergent ecosystems like the mussel beds and clam beds. Three species of brittle stars (Ophiuroidea) were discovered in the Haima cold seep fields, of which Ophiophthalmus serratus and Histampica haimaensis were found on top of or within mussel beds and clam beds, whereas Amphiura sp. was only collected from muds in the clam bed assemblage. Here, we evaluated the genetic signatures of micro-environmental adaptation of brittle stars to cold seep through the comparison of mitogenomes. This study provided two complete mitogenome sequences of O. serratus and Amphiura sp. and compared with those of H. haimaensis and other non-seep species. We found that the split events of the seep and non-seep species were as ancient as the Cretaceous period (∼148–98 Mya). O. serratus and H. haimaensis display rapid residue mutation and mitogenome rearrangements compared to their shallow or deep-sea relatives, in contrast, Amphiura sp. only show medium, regardless of nucleotide mutation rate or mitogenome rearrangement, which may correlate with their adaptation to one or two micro-ecosystems. Furthermore, we identified 10 positively selected residues in ND4 in the Amphiura sp. lineage, suggesting important roles of the dehydrogenase complex in Amphiura sp. adaptive to the cold seep environment. Our results shed light on the different evolutionary strategies during colonization in different micro-environments.

A New Genus and Species of Brittle Star (Ophiuroidea: Ophioleucida) from the Upper Triassic (Carnian) of Northern Vietnam

The fossil record of brittle stars, one of the five extant classes of echinoderms, is still rather poorly known. In particular for the Triassic Period, occurrences published to date are strongly biased toward Europe, with only two exhaustively described taxa recorded from the East Asian part of the Tethys Ocean. Here, we record new ophiuroids from the Carnian (Upper Triassic) of the Me area in Ninh Binh Province, Vietnam. The fossils comprise articulated disks and arm fragments preserved as external molds, all original calcite dissolved. We introduce a new genus and species, Triadoleucella meensis, for these specimens that represent the oldest known member of the order Ophioleucida. The ophiuroids were found in mudstones deposited in outer shelf environments below storm wave base. The intact articulation, combined with random orientation and intense fragmentation of individuals suggest effective burial by downslope mudflow prior to or soon after death.

Overlooked for over a century: Ophioderma occultum sp. nov. (Echinodermata), a new species of brittle star from the Eastern Pacific

ABSTRACT We describe a new species of ophiodermatid brittle star from the Eastern Pacific: Ophioderma occultum sp. nov. This species has been mistakenly recorded since 1899 as a colour phase of one of its congeners, Ophioderma panamense. However, the integrative use of morphological and molecular data, and comparison with type material of other Eastern Pacific Ophioderma, led to its differentiation as a novel species. Ophioderma occultum sp. nov. is characterised by having radial shields and adoral shields covered with granules, dorsal arm plates divided typically into two pieces, and a particular colour pattern: a dark grey to brown body, and arms with subtle lighter transverse bands and parallel longitudinal white bands over some median and distal segments. Molecular information based on the mitochondrial genes cytochrome oxidase subunit I (COI) and 16S also supported the species’ validity, coinciding with the morphological observations. In particular, the molecular marker 16S had not been used before for species delimitation in this genus and was proven here to be resolutive. In contrast to most species of Ophioderma from the area, Ophioderma occultum sp. nov. shows a restricted distribution to the northern Mexican Pacific (Gulf of California and islas Revillagigedo). This new species is the 10th Ophioderma described from the Eastern Pacific and the 34th worldwide. http://www.zoobank.org/urn:lsid:zoobank.org:pub:A5FFAC55-E5BE-42F6-8371-7B745911F157

Miniaturization during a Silurian environmental crisis generated the modern brittle star body plan

Pivotal anatomical innovations often seem to appear by chance when viewed through the lens of the fossil record. As a consequence, specific driving forces behind the origination of major organismal clades generally remain speculative. Here, we present a rare exception to this axiom by constraining the appearance of a diverse animal group (the living Ophiuroidea) to a single speciation event rather than hypothetical ancestors. Fossils belonging to a new pair of temporally consecutive species of brittle stars (Ophiopetagno paicei gen. et sp. nov. and Muldaster haakei gen. et sp. nov.) from the Silurian (444–419 Mya) of Sweden reveal a process of miniaturization that temporally coincides with a global extinction and environmental perturbation known as the Mulde Event. The reduction in size from O. paicei to M. haakei forced a structural simplification of the ophiuroid skeleton through ontogenetic retention of juvenile traits, thereby generating the modern brittle star bauplan.

Spatiotemporal variations in the population dynamics of a few prominent brittle star species (Echinodermata: Ophiuroidea) from the intertidal flat of the Veraval coast, Gujarat, India

The present communication reports the spatiotemporal variation in the population dynamics of three prominent Ophiuroidea species: Amphipholis squamata, Ophiactis savignyi and Ophiocomella sexradia at the rocky intertidal zone at Veraval (21°35’ N, 69°36’ E) Gujarat, off the Arabian Sea. The two sampling areas with different substratum and community structures were investigated from April 2019 to March 2020. Brittle stars were found inhabited in the coralline bed, zoanthid bed, algal holdfast, rock pool crevices and underneath rocks in the studied coastal areas. A. squamata was the most abundant species followed by O. savignyi and O. sexradia at the Veraval coast. The current study described a few remarkable revelations between the patches of coralline algae and Ophiuroidea abundance. Brittle star population revealed major spatial variations between both sampling sites. Cluster analysis and nMDS support population abundance in a seasonal pattern distribution.

Range extension and first record of the deep-sea brittle star Ophiactis abyssicola (Echinodermata: Ophiuroidea) in Canadian waters

AbstractThis paper presents the first records of the brittle star Ophiactis abyssicola in Canadian waters and range extensions of up to 1900 km in the Northwest Atlantic from previously known locations. Samples were collected off northern Labrador and the northern portion of insular Newfoundland (eastern Canada) at 433 and 1097 m depths, respectively. This newly recorded species of brittle star from the bathyal zone off Newfoundland and Labrador adds to the marine biodiversity of Canada and to the general distribution knowledge of O. abyssicola.

Description of a New Brooding Species of Ophiodelos (Echinodermata: Ophiuroidea) from Japan.

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

Long-term response of marine benthic fauna to thin-layer capping with powdered activated carbon in the Grenland fjords, Norway.

The Grenland fjords in Norway have a long history of contamination by large emissions of dioxins and mercury. As a possible sediment remediation method in situ, thin-layer capping with powdered activated carbon (AC) mixed with clay was applied at two test sites at 30m and 95m depth in the Grenland fjords. This study presents long-term effects of the AC treatment on the benthic community structure, i.e. nine years after capping. Capping with AC significantly reduced the number of species, their abundance and biomass at the two test sites, compared to uncapped reference sites. At the more shallow site, the dominant brittle star species Amphiura filiformis disappeared shortly after capping and did not re-establish nine years after capping. At the deeper site, the AC treatment also caused long-lasting negative effects on the benthic community, but some recovery was observed after nine years. Ecological indices used to assess environmental status did not capture the impaired benthic communities caused by the capping. The present study is the first documentation of negative effects of powdered AC on marine benthic communities on a decadal scale. Our results show that the benefits of reduced contaminant bioavailability from capping with AC should be carefully weighed against the cost of long-term detrimental effects on the benthic community. More research is needed to develop a thin-layer capping material that is efficient at sequestering contaminants without being harmful to benthic species.

Experimental evidence of minimal effects on octocoral hosts caused by the introduced ophiuroid Ophiothela mirabilis

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

Phylogeography of the Brittle Star Ophiura sarsii Lütken, 1855 (Echinodermata: Ophiuroidea) from the Barents Sea and East Atlantic

Ophiura sarsii is a common brittle star species across the Arctic and Sub-Arctic regions of the Atlantic and the Pacific oceans. Ophiurasarsii is among the dominant echinoderms in the Barents Sea. We studied the genetic diversity of O.sarsii by sequencing the 548 bp fragment of the mitochondrial COI gene. Ophiurasarsii demonstrated high genetic diversity in the Barents Sea. Both major Atlantic mtDNA lineages were present in the Barents Sea and were evenly distributed between the northern waters around Svalbard archipelago and the southern part near Murmansk coast of Kola Peninsula. Both regions, and other parts of the O.sarsii range, were characterized by high haplotype diversity with a significant number of private haplotypes being mostly satellites to the two dominant haplotypes, each belonging to a different mtDNA clade. Demographic analyses indicated that the demographic and spatial expansion of O.sarsii in the Barents Sea most plausibly has started in the Bølling–Allerød interstadial during the deglaciation of the western margin of the Barents Sea.