Abyssal Species Research Articles

New Genera, Species, and observations on the biology of Antarctic Valvatida (Asteroidea).

Assessment of Antarctic taxonomic diversity for asteroids and other taxa for poorly studied or unknown regions, such as the deep-sea, will be important for our understanding of these understudied habitats. Eleven new species and a new genus are described from three families (Asterinidae, Goniasteridae, Solasteridae) within the Valvatida, nearly all of which were collected from deep-sea settings below 1000 m by the US Antarctic Research Program in the 1960s. A new subfamily, the Kampylasterinae subfam. nov. is designated for Kampylaster and Astrotholus nov. gen. which were supported as sister taxa on a monophyletic clade within the Asterinidae. Astrotholus nov. gen. is described to accommodate "Anseropoda" antarctica and four new bathyal and abyssal species, which are a significant morphological divergence from the typological definition of Anseropoda. New species of the goniasterid Notioceramus and the solasterid Paralophaster are also described from bathyal depths (2000-3000 m). Paralophaster ferax n. sp. is among the deepest asteroids known to brood, is the first brooding species within Paralophaster and the second species in the Solasteridae known to brood. Following examination of the type and molecular data, Lophaster densus is found to be included within Paralophaster. A review of Antarctic Lophaster species shows additional specimens of Lophaster abbreviatus which support it as a distinct species from Lophaster stellans. New occurrence data for bathyal Antarctic Asteroidea as well as unusual-gut content observations of shallower-water species are also included.

Cosmopolitan abyssal lineages? A systematic study of East Pacific deep-sea squat lobsters (Decapoda: Galatheoidea: Munidopsidae)

Munidopsid squat lobsters are among the most abundant decapods at abyssal depths and the most diverse squat lobster group in the East Pacific region. During recent cruises along the East Pacific, many deep-sea squat lobsters were collected. Among these, we described five new munidopsid species supported both by morphological characters and molecular phylogenetics: Munidopsis girguisi sp. nov., M. nautilus sp. nov., M. testuda sp. nov., M. cortesi sp. nov. and M. hendrickxi sp. nov. We also report new records of several Munidopsis species across the East Pacific that increase the species distribution ranges. Here, we reconstructed the phylogenetic relationships of the East Pacific species in relation to other Galatheoidea using one nuclear and two mitochondrial gene fragment(s); we also performed single locus species delimitation analyses to explore the species status of various East Pacific munidopsid taxa. The new taxa were photographed, illustrated and imaged with micro-computed tomography. The phylogenetic results show that: (1) Janetogalathea californiensis, previously included in the family Galatheidae, nests within Munidopsidae; (2) the phylogenetic position of Phylladiorhynchus and Coralliogalathea as belonging in Galatheidae is not supported; and (3) Munidopsis is paraphyletic, agreeing with recent systematic hypotheses. Short genetic distances and species delimitation analyses suggested that a clade mostly constituted by abyssal species might include fewer species than currently considered, as species show a wider geographic range than previously considered, conforming with traditional hypotheses of cosmopolitanisms in abyssal species. ZooBank: urn:lsid:zoobank.org:pub:CED9EB18-7061-47A7-B2FF-7F1DAFCC7B12.

First record of the family Caprellidae (Amphipoda: Senticaudata) from the abyssal zone of the Bering Sea with description of a new species of Cercops

Three species of the amphipod family Caprellidae were collected in the area of the submarine Piip Volcano, the northwestern Bering Sea, during 75-th and 82-nd research cruises aboard the R/V Akademik M.A. Lavrentyev in 2016 and 2018 using the ROV Comanche-18. Two morphospecies of the genus Caprella (Caprellinae) were found on the Northern Summit of the Piip Volcano (depth 373 m) and on its northern slope (749–986 m). A new species, Cercops caecus Kireev and Golovan sp. nov. (Paracercopinae), was sampled in the abyssal zone adjacent to its southern slope (3362 m), where it was found on hydroids growing on a hexactinellid sponge. The new species differs from all other species of the genus by the lack of eyes and the presence of two pairs of gills in contrast to three paired gills found in the other congeners. This is the first record of an abyssal species of the subfamily Paracercopinae, whose other representatives are known from the shelf and the upper bathyal zones of the North Pacific, Arctic, and North Atlantic. This finding demonstrates the parallel processes of colonization of deep-sea habitats occurring in different subfamilies of Caprellidae. An updated diagnosis and a key to the Cercops species are provided. For the first time for Paracercopinae, data on the molecular marker (18S rRNA) was obtained.

Comparative Analysis of the Mitochondrial Genome of Galatheanthemum sp. MT-2020 (Actiniaria Galatheanthemidae) From a Depth of 9,462 m at the Mariana Trench

The hadal zone, which represents the deepest marine habitat on Earth (6,000–11,000 m), is a harsh environment mainly characterized by extremely high hydrostatic pressure, and this habitat is believed to have a high degree of endemism. The deep-sea anemone family Galatheanthemidae comprises two valid species exclusively from the hadal; however, no other information about this family is currently available. In the present study, a sea anemone was collected from a depth of 9,462 m at the Mariana Trench and was defined as Galatheanthemum sp. MT-2020 (Actiniaria Galatheanthemidae). The mitochondrial genome of Galatheanthemum sp. MT-2020 was circular, was 16,633 bp in length, and contained two ribosomal RNA genes, 13 protein-coding genes and two transfer RNA genes. The order of the genes of Galatheanthemum sp. MT-2020 was identical to that of the majority of the species of the order Actiniaria. The value of the AT-skew was the lowest in the whole mitochondrial genome, with a positive GC skew value for the atp8 gene, while other species, except Antholoba achates, had the negative values of the GC skew. Galatheanthemum sp. MT-2020 was clustered with another abyssal species, Paraphelliactis xishaensis, in the phylogenetic tree, and these species diverged in the early Jurassic approximately 200 Mya from the shallow-sea species. The usage ratio of valine, which is one of the five amino acids with the strongest barophilic properties, in the mitochondrial genomes of the two abyssal species was significantly higher than that in other species with habitats above the depth of 3,000 m. The ω (dN/dS) ratio of the genomes was 2.45-fold higher than that of the shallow-sea species, indicating a slower evolutionary rate. Overall, the present study is the first to provide a complete mitogenome of sea anemones from the hadal and reveal some characteristics that may be associated with adaptation to an extreme environment.

Description of a new and widely distributed species of Bathypathes (Cnidaria: Anthozoa: Antipatharia: Schizopathidae) previously misidentified as Bathypathes alternata Brook, 1889.

For many years an undescribed species of the genus Bathypathes has been misidentified as Bathypathes alternata Brook, 1889 (a species currently re-assigned to the genus Alternatipathes). This new species is rather common at mid- and lower bathyal depths of the Pacific, Atlantic and Indian oceans, often in areas with high concentrations of commercially valuable cobalt-rich ferromanganese crusts, where it was observed in underwater photo and video transects to occur in high densities. Under the name B. alternata this species is recorded in several inventories and databases. There is an urgent need for a formal description of this misidentified and widely distributed species to avoid further confusion. The new species is superficially similar to A. alternata in having a monopodial corallum and simple, bilateral and alternately arranged pinnules. However, it differs from the former in that it has an upright corallum with a straight pinnulated part (vs. a horizontally bent pinnulated part), pinnules of uniform length and density (vs. decreasing regularly distally), and a constant distal angle formed by the pinnules and the stem along different parts of the corallum (vs. a decreasing distal angle near the top). The new species can therefore be easily distinguished from A. alternata in underwater imagery. We formally describe this new species in the genus Bathypathes and assign it the new name B. pseudoalternata. An extensive synonymy list with previous misidentified records is provided. To evaluate the distributional patterns of the new species we review the geographic distribution of antipatharians reported below 800 m. The majority of the hitherto described lower bathyal and abyssal species have been recorded from one biogeographic province; however, 20 species are known from more than two provinces, and only three species are widely distributed (>5 provinces), including the newly described Bathypathes pseudoalternata. Members of the family Schizopathidae, to which the new species belongs, represent the majority of the lower bathyal (50.54%) and abyssal (82.35%) species.

Revision of the 'dragon-head cusk eels of the genus Porogadus (Teleostei: Ophidiidae), with description of eight new species and one new genus.

The ophidiid genus Porogadus occurs between 800 and 5300 m in the tropical and subtropical world oceans. Fifteen nominal species have been described since 1878 and most of them until 1902. The genus has been highlighted as needing revision in recent compilations about ophidiiforms and here we present the first comprehensive review. Twelve of the previously described species are here accepted as valid with two being moved to the newly established genus Tenuicephalus n. gen. that encompasses fishes differing from those of Porogadus in the extremely weak ossification, the stout head, absence of head spines and absence of the triple lateral line system considered typical for Porogadus and a reduced dentition. In addition, eight new species are described: Porogadus caboverdensis, P. dracocephalus, P. lacrimatus, P. mendax, P. solomonensis, P. turgidus, Tenuicephalus multitrabs and T. squamilabrus. The species of Porogadus show a distinctive depth segregation with the majority of species having a demersal bathyal life-style between 800 and 3500 m and other species being more or less exclusively restricted to abyssal depths below 3000 m. The biogeographic distribution pattern of bathyal groups shows putative species pairs in the Atlantic versus the eastern Pacific and a clear separation of eastern Pacific from Indo-West Pacific species. The geographic effects and timing are being discussed that may have led to this speciation events. Generally, we found widely distributed species that are found far away from continental masses and others restrained to continental slopes and sometimes exhibiting regionalism. In abyssal depth, the Cabo Verde and Canary basins off NW-Africa have yielded three exclusive species, but it is uncertain at this stage whether this could represent a sampling bias with this area being extensively sampled by the Discovery research vessel (BMNH) over the years from 19701998. Another instance of a potentially endemic abyssal species is that of Porogadus melanocephalus in the Bay of Bengal. The latter has been caught with 45 specimens in a single trawl, representing the highest number of Porogadus specimens collected in any trawl and indicating that these fishes may actually not be as rare as one might assume from the literature.

THE HALACARID GENUS LOHMANNELLA (HALACARIDAE, ACARI): LIST OF SPECIES, NOTES ON CHARACTERS, DISTRIBUTION, ECOLOGY AND A TABULAR KEY

Presently, 39 Lohmannella species are accepted as valid, but future examinations may prove some of them to be junior synonyms of others. This article lists the most important descriptive papers, as well as the former names for each of the 39 species. The characters of another five species, known by their adults, are outlined but not given a name. Based on the published data, short diagnoses as well as notes on the distribution and habitats are added. In addition, the poorly known female of Lohmannella bihamata is described and illustrated. This article provides a table of morphological characters that are meant to facilitate the identification of Lohmannella species. The genus Lohmannella is spread worldwide, inhabiting all water depths and all climatic zones; its representatives live in marine and fresh water. Although the majority of Lohmannella species have been found at sea, five species have been recovered from fresh or slightly brackish water. In the following sentences, the number of unnamed species is given in square brackets. Records of 33 [plus two] marine species are exclusively from the littoral and/or bathyal zone (0–1,000 m deep); records of three [plus three] species are from the deep sea (deeper than 1,000 m); and one record is from the littoral / deep sea depth range. Most species have been found in the temperate and polar areas: namely, 12 [plus two] have been recorded north of 23°N and 20 south of 23°S. The data from the tropics include a single shallow water (0–200 m deep) record, one unnamed species from the 400–520 m depth and one [plus two] species from the depth of more than 1,000 m. Most southern hemisphere shallow water species are morphologically distinct from the bathyal and abyssal species, as well as from the northern hemisphere species.

Rediscovery of the abyssal species Peniagone leander Pawson and Foell, 1986 (Holothuroidea: Elasipodida: Elpidiidae): the first record from the Mariana Trench area

The elpidiid holothurianPeniagone leanderPawson and Foell, 1986 is recorded for the first time from the Mariana Trench area at a depth of 5 571 m. The type description of this species was based on only in-situ photographs.P. leanderis re-described and illustrated based on a preserved material and in-situ photographs taken on the seabed. The 16S rRNA was also obtained from the specimen and submitted to GenBank. This is the fourth discovery of this species, extending its bathymetric range in the western Pacific Ocean.

Xenophyophores (Rhizaria, Foraminifera), including four new species and two new genera, from the western Clarion-Clipperton Zone (abyssal equatorial Pacific)

The Clarion-Clipperton Zone (CCZ) occupies a vast swathe of the Pacific with extensive polymetallic nodule deposits. Eastern and central parts host diverse assemblages of xenophyophores (megafaunal agglutinated foraminifera). Here we describe xenophyophores obtained using a Remotely Operated Vehicle from the western CCZ. Eleven distinct forms include two known species, Stannophyllum zonarium Haeckel, 1888 and Aschemonella monile Gooday and Holzmann in Gooday et al., 2017b. Another four are described as new species based on morphological and genetic data. In Abyssalia foliformis gen. nov., sp. nov. and Abyssalia sphaerica sp. nov. the flattened or spherical test comprises a homogeneous framework of sponge spicules. Psammina tenuis sp. nov. has a delicate, thin, plate-like test. Moanammina semicircularis gen. nov., sp. nov. has a stalked, fan-shaped test and is genetically identical to ‘Galatheammina sp. 6’ of Gooday and co-workers from the eastern CCZ. Sequence data revealed a spherical ‘mudball’, which disintegrated and cannot be formally described, to be a novel xenophyophore. Finally, four morphospecies are represented by dead tests: Psammina spp., Reticulammina sp., and an unknown genus with a unique test structure. This collection enhances our knowledge of Pacific xenophyophore diversity and provides the first genetic confirmation of wide geographic ranges for abyssal species.

From “source to sink” – A new perspective on the past dynamics of the Murray Canyon Group from benthic foraminiferal communities

We present fossil benthic foraminiferal assemblage data from marine sediment core SS02/06-GC2 located in the abyssal plain of the Murray Canyon Group (offshore South Australia). The sedimentological characteristics indicate the presence of turbidite deposits showing classical Bouma-like sequences, dated between ~40 and 12 cal ka BP. These results confirm the previous interpretation of the observed large deep-water holes in the abyssal area where the core was sampled as being gouged by surges of high-energy turbidity currents. The presence of good indicator taxa and unique assemblages occupying specific bathymetric depths allows the determination of the source origin of the sediments making the turbidites. Three distinct faunal groups are found: 1) mostly shelf species, 2) mostly bathyal species and 3) mostly abyssal species. In the sediment core, these groups present a quasi-systematic succession, with nearly all Bouma-like sequences starting with the dominance of bathyal species in the coarse-grained base, followed by the dominance of shallow species in the silty part, and finally with abyssal species in the clays. To explain such phenomena, turbidites triggered by mixed hyperpycnal/hypopycnal flow processes and turbidity currents during periods of river floods are considered for the first time within the Murray Canyon Group. They are mostly related to periods of increased fluvial discharges during wet phases in the Murray-Darling Basin. • The presence of turbidite deposits showing classical Bouma-like sequences. • Relative abundance of benthic bathymetric foraminiferal groups indicates the source of turbidites. • The presence of upper inner shelf/estuarine foraminifera indicates a river in flood origin. • A strong link with humid climate over the Murray-Darling Basin is hypothesized.

Sensitivity of Benthic Foraminifera to Carbon Flux in the Western Tropical Pacific Ocean

ABSTRACT We investigated benthic foraminiferal species as tracers for carbon export flux in the Indo-Pacific warm pool (International Ocean Discovery Program Expedition 363). In core tops, the distribution of lower bathyal and upper abyssal species can be separated into two distinct groups. Foraminifera belonging to the high carbon flux (>3.5 g C m−2 year−1), ‘warm’ (>3.5°C) group are Bolivina robusta, Bulimina aculeata, Globobulimina pacifica, Hoeglundina elegans, Laticarinina pauperata, and Cibicidoides pachyderma. The lower carbon flux, ‘cold’ group includes Oridorsalis umbontus, Uvigerina bifurcata, and Planulina wuellerstorfi. An index based on the percent ‘warm’ assemblage with respect to the total ‘warm’ plus ‘cold’ species in core-top samples correlates significantly with carbon flux (r = 0.91, P = 0.0007) and modern bottom water temperatures (r = 0.94, P = 0.0002). When applied to down-core species abundances based on core catchers spanning the late Miocene through Pleistocene, we observed that sites from the northwestern Australian margin show marked changes in the ‘warm’ index, suggesting a large paleoenvironmental signal in this dynamic region. At Papua New Guinea, down-core abundances of the ‘warm’ group are highest (>80%), consistent with high organic matter input via the Sepik River. At the deeper of the two sites, down-slope movement in this tectonically unstable region may have contributed to organic matter input. At Manus Basin, the ‘warm’ species abundances are also relatively high and covary with the percent abundance of Uvigerina proboscidea, providing further evidence for the use of this index as a tracer for carbon flux. Overall, this study contributes evidence for the relationship between benthic foraminiferal assemblages and carbon export flux in the Indo-Pacific warm pool, suggesting that the ‘warm’ index can be used as a tracer for paleoproductivity.

NOO3D: A procedure to perform 3D species distribution models

There is consensus surrounding the need to include a third dimension when estimating Species Distribution Models (SDMs), which is of special interest for marine species. Application of the third dimension is, however, rarely available, thus users are obliged to manually combine 2D SDM outputs (i.e., suitability or presence/absence maps) for 3D distribution generation. Herein, the Niche of Occurrence 3D (NOO3D) is presented, which is a new, simple modelling procedure that provides 3D distributions using both 3D occurrence samples and environmental datasets that consist of one layer per depth value. NOO3D performance was evaluated using five virtual marine species to avoid errors associated with real data sets (three pelagic species, with wide, medium, and narrow distributions, respectively, a mesopelagic species and an abyssal species). These virtual species are distributed across the North Atlantic Ocean and were built to a 0.5° x 0.5° resolution and considering 49 depth levels (from 0.43 m to an undersea depth of 5274.7 m). NOO3D results were also compared to those provided by 3D Alpha Shapes and Maximum Entropy (MaxEnt). The True Positive Rate (TPR), or sensitivity, True Negative Rate (TNR), or specificity, False Positive Rate (FPR), or commission error, and False Negative Rate (FNR), or omission error, were employed in order to facilitate comparison between methods. MaxEnt performed best for TPR, TSS and FNR, and Alpha Shape 3D performed best for FPR and TNR. NOO3D was always the second-ranked method for all metrics considered, which indicates that it was the most suitable method. The provided results indicate that NOO3D can be considered a viable alternative in achieving three-dimensional species distribution models.

Diversity and distribution of Ischnomesidae (Crustacea: Isopoda: Asellota) along the Kuril-Kamchatka Trench – A genetic perspective

The aim of this study was to investigate the diversity and distribution of the asellote isopod family Ischnomesidae in the hadal and abyssal of the Kuril-Kamchatka Trench (KKT) and adjacent Sea of Okhotsk and the neighboring northwest Pacific Basin. Ischnomesids were sampled during two expeditions (SokhoBio & KuramBio II) in depths between 3299 and 9584 m. Subsequent to morphological identifications, mitochondrial COI was successfully sequenced for 208 of the 298 sampled specimens. Based on two computational approaches (ABGD and GMYC) 24–45 putative species (lineages) could be delimited. The initially 21 defined morphospecies matched poorly with these COI lineages, in particularly females and juveniles were differently assigned. FortimesusKavanagh and Wilson, 2007 was found to be the most abundant and diverse genus, in particular in the hadal. The hadal of the KKT had a higher species diversity (6–9 species) than the adjacent Sea of Okhotsk (1 species), but lower diversity than the abyssal northwest Pacific Basin (15–24 species). Most species were restricted to a single studied area, wider distributions of ~300 km were mainly observed for hadal species within the KKT and only to a lesser degree for abyssal species. Species distributions across the KKT were rare and again predominately observed for hadal species. The abyssal species were either restricted to one side of the KKT or the genetic distances between populations on the opposite sides of the KKT were very high. This implies that the KKT serves as an isolation barrier for poorly dispersing benthic species like the herein studied Ischnomesidae.

Not as clear as expected: what genetic data tell about Southern Hemisphere corellids (Ascidiacea: Phlebobranchia)

ABSTRACTThe morphology of corellids (Ascidiacea) has led to numerous misidentifications and wrong taxonomic decisions over the last century. Paradoxically, the morphology has also enabled new species to be identified and ancient entities to be re-established in the Southern Hemisphere. There are many examples of the integration of morphological and molecular data leading to the same taxonomic conclusions, and therefore we aimed to analyse DNA sequences of the gene cytochrome oxidase subunit I of currently accepted species within Corellidae occurring in the Southern Hemisphere. Haplotype networks along with phylogenetic trees and genetic distances not only corroborate the distinction between Corella eumyota and Corella antarctica, but also separate the latter into two potential groups, one located in Terre Adélie and the other in the Antarctic Peninsula (AP). Furthermore, the C. antarctica group from the AP was closely related to the allied abyssal species, Corynascidia suhmi from Terre Adélie. Although the number of new sequences is reduced, our results are congruent with a long record of suspicion on the matter and stress the need for deeper and more extensive investigation of this ascidian family.

Food safety assessment of heavy metals in uncommon and abyssal fish and cephalopod from the Tyrrhenian Sea

The spread of non-native species in the Mediterranean Sea, due to Lessepsian migration and tropicalization, as well as the use of “non-selective” fishing practices, causes frequently the capture of uncommon and abyssal species, that can be sold in seafood market. This could represent a risk for food safety, since some of these species are not listed in the European Union (EU) regulations for human consumption. Heavy metal contamination (lead, cadmium, mercury and arsenic) was evaluated, for the first time, in 12 uncommon lessepsian and abyssal finfish and cephalopod species, caught in the Southern Tyrrhenian Sea. Mercury exceeded the maximum limit set by the EU in some species, while lead and cadmium concentrations were compliant. Total inorganic arsenic was detected in all species, in a wide concentration range. Therefore, inclusion in the EU regulations of all these species is suggested to reduce the risk of consumer exposition to heavy metals.

New record of Munidopsis taiwanica (Decapoda, Anomura) from a mud volcano field in the Mariana Trench, with in-situ observations on habitat

Squat lobsters are prevalent in chemosynthetic environments but have been insufficiently studied in mud volcano habitats. An abyssal species,Munidopsis taiwanicaOsawa, Lin & Chan, 2008 was recently collected in a mud volcano field in the Mariana Trench at a depth greater than 5000 m, which represents a new distributional record. Its diagnostic characters are presented in this study. In-situ observation suggested thatM. taiwanicawas closely associated with this chemosynthetic environment and probably exhibited camouflage behaviour by attaching seafloor sediments onto its body.Munidopsis taiwanicais the first confirmed species of squat lobster found in the mud volcano environment, and currently represents the deepest record (5491 m) of squat lobsters in the world.

Abyssal Solenogastres (Mollusca, Aplacophora) from the Northwest Pacific: Scratching the Surface of Deep-Sea Diversity Using Integrative Taxonomy

Solenogastres (Aplacophora) is a small clade of marine, shell-less worm-molluscs with close to 300 valid species. Their distribution ranges across all oceans, and whereas the vast majority of species has been collected and described from the continental shelf and slope, only few species are known from depths below 4000 m. Following traditional taxonomy, identification of specimens to species level is complex and time-consuming and requires detailed investigations of morphology and anatomy – often resulting in the exclusion of the clade in biodiversity or biogeographic studies. During the KuramBio expedition (Kuril-Kamchatka Biodiversity Studies) to the abyssal plain of the Northwest Pacific and the Kuril-Kamchatka trench, 33 solenogaster specimens were sampled from 4830 m to 5397m. Within this study we present an efficient workflow to address solenogaster diversity, even when confronted with a high degree of singletons and minute body sizes, hampering the use of single individuals for multiple morphological and molecular approaches. We combine analyses of external characters and scleritome with molecular barcoding based on a self-designed solenogaster specific set of mitochondrial primers. Overall we were able to delineate at least 19 solenogaster lineages and identify 15 species to family level and beyond. Based on our approach we identified three key lineages from the two regionally most species-rich families (Acanthomeniidae and Pruvotinidae) for deeper taxonomic investigations and describe the novel abyssal species Amboherpia abyssokurilensis sp. nov. (Cavibelonia, Acanthomeniidae) using microanatomical 3D-reconstructions. Our study more than doubles the previous records of solenogaster species from the Northwest Pacific and its marginal seas. Almost all lineages are reported for the first time from the region of the (Northwest) Pacific, vastly expanding distribution ranges of the respective clades. Moreover it doubles the number of Solenogastres collected from abyssal depths on a global scale and underlines the lack of exploratory α-diversity work in the abyssal zone for reliable species estimates in marine biodiversity.

Systematic revision of the Antarctic gastropod family Newnesiidae (Heterobranchia: Cephalaspidea) with the description of a new genus and a new abyssal species

Systematic revision of the Antarctic gastropod family Newnesiidae (Heterobranchia: Cephalaspidea) with the description of a new genus and a new abyssal species

Deep-sea echinoderms of the Sea of Okhotsk

New samples of abyssal echinoderms taken in the Sea of Okhotsk by the SokhoBio expedition have been examined and analyzed. Taking into account this new data, 34 echinoderm species are distributed deeper than 2000m in the Sea of Okhotsk. Among them, 10 species are found in the Sea of Okhotsk for the first time, and 6 species are found in the abyssal zone of the Sea of Okhotsk for the first time. The species richness of the abyssal echinoderm fauna in the North-West Pacific areas (north of 30°N and west of 180°E) negatively correlates with the level of their geomorphological isolation: the higher the level of isolation of the area, the lower the species richness of its abyssal fauna. The number of echinoderm species in the abyssal zone is found to be 9 in the most isolated Sea of Japan, 34 species in the semi-enclosed Sea of Okhotsk, and 47 species in the least isolated Bering Sea. More than 58 species occur in the open North-West Pacific abyssal area. The new data on echinoderms indicates both submergence of the sublittoral-bathyal species and dispersal of the abyssal species through the deep straits into the Kuril Basin of the Sea of Okhotsk. Among the abyssal echinoderms of the Sea of Okhotsk, pseudoabyssal and true abyssal species account for ~24% and ~35% respectively. The influence of the Antarctic and West Pacific deep-sea centers of fauna redistribution is discussed.

Fatty acid composition in the white muscle of Cottoidei fishes of Lake Baikal reflects their habitat depth

Lake Baikal is a unique freshwater environment with maximum depths over 1600 m. The high water pressure at the lakebed strengthens the solidifying effect of low water temperature on animal tissue lipids, and thus the effective temperatures in the depths of the lake equal subzero temperatures in shallow waters. Cottoidei species has colonized the different water layers of the lake, and developed different ecology and physiology reflected in their tissue biochemistry. We studied by gas chromatography the composition of fatty acids (FAs), largely responsible for tissue lipid physical properties, in the white muscle tissue of 13 species of the Cottoidei fish; five benthic abyssal, six benthic eurybathic and two benthopelagic species. The FA profiles reflected habitat depth. The muscles of the deepest living species contained little polyunsaturated FAs (PUFAs) and were instead rich in monounsaturated FAs (MUFAs), which may be due to occasional weak food web links to the PUFA-rich primary producers of the photic water layer, high MUFA supply from their benthic diet, and conversion of saturated FAs (SFAs) to MUFAs in the tissues of the fish. Despite the MUFA percentage among the abyssal species reached even 50% (by weight) of total FAs, the PUFA percentage still remained above 20% in every species. The muscle MUFA/SFA ratio correlated negatively with the PUFA content of the fish muscle, suggesting viscosity control integrating the fluidity contributions from the dietary PUFAs and potentially endogenous MUFAs.