Tentacular diversity in deep-sea deposit-feeding holothurians: implications for biodiversity in the deep sea

The tentacles of deep-sea holothurians show a wide range of morphological diversity. The present paper examines gross tentacle morphology in surface deposit feeding holothurians from a range of bathymetric depths. Species studied included the elasipods: Oneirophanta mutabilis, Psychropotes longicauda and Benthogone rosea and the aspidochirotids: Paroriza prouhoi, Pseudostichopus sp., Bathyplotes natans and Paroriza pallens. The sympatric abyssal species Oneirophanta mutabilis, Psychropotes longicauda and Pseudostichopus sp. show subtle differences in diet and the structure and filling patterns of the gut that suggest differences in feeding strategies which may represent one mechanism to overcome competition for food resources in an environment where nutrient resources are considered to be, at least periodically, limiting. Interspecific differences in tentacle functional morphology and digestive strategies, which reflects taxonomic diversity could be explained in terms of Sanders'; Stability–Time Hypothesis. Since different tentacle types will turn over sediments to different extents, their impact on sedimentary communities will be enormous so that high diversity in meiofaunal communities may be explained most simply by Dayton and Hessler's Biological Disturbance Hypothesis.

New microsatellite loci for the longnose velvet dogfish Centroselachus crepidater (Squaliformes: Somniosidae) and other deep sea sharks

The continuing over-exploitation of traditional coastal stocks has resulted in the shift of commercial fishing towards deep-sea ecosystems in many parts of the world. The effects on target and non-target species have been dramatic; particularly for the deep-sea sharks. With the aim of providing tools that will allow the assessment of population genetic structure of Centroselachus crepidater, novel microsatellite loci have been developed for this deep-sea elasmobranch. Seven of these markers showed between 3 and 7 alleles per locus in two North Atlantic populations, with observed and expected heterozygosities between 0.18-0.95 and 0.25-0.82, respectively. Additionally, ten loci cross-amplify in other Elasmobranch species.

Novel microsatellite loci for a deep sea fish (Macrourus berglax) and their amplification in other grenadiers (Gadiformes: Macrouridae)

Over-exploitation of traditional coastal stocks and a rising demand for seafood have resulted in the shift of commercial fishing towards less-known, deep-sea species in many parts of the world. Yet, the lack of knowledge of the biology, ecology and life-history of these species represents a serious impediment for establishing sound stock management plans. With the aim of providing tools that will allow assessment of the population genetic structure of Macrourus berglax, we have isolated and characterised a suite of novel microsatellite loci for this deep sea grenadier. Eight of these markers showed between 4 and 11 alleles per locus in two distant North Atlantic populations, with observed and expected heterozygosities between 0.17-0.83 and 0.35-0.87, respectively. Importantly, eight of these loci also cross-amplify in other Macrourid species. 

A primer for use of genetic tools in selecting and testing the suitability of set-aside sites protected from deep-sea seafloor massive sulfide mining activities

Seafloor massive sulfide (SMS) mining will likely occur at hydrothermal systems in the near future. Alongside their mineral wealth, SMS deposits also have considerable biological value. Active SMS deposits host endemic hydrothermal vent communities, whilst inactive deposits support communities of deep water corals and other suspension feeders. Mining activities are expected to remove all large organisms and suitable habitat in the immediate area, making vent endemic organisms particularly at risk from habitat loss and localised extinction. As part of environmental management strategies designed to mitigate the effects of mining, areas of seabed need to be protected to preserve biodiversity that is lost at the mine site and to preserve communities that support connectivity among populations of vent animals in the surrounding region. These "set-aside" areas need to be biologically similar to the mine site and be suitably connected, mostly by transport of larvae, to neighbouring sites to ensure exchange of genetic material among remaining populations. Establishing suitable set-asides can be a formidable task for environmental managers, however the application of genetic approaches can aid set-aside identification, suitability assessment and monitoring. There are many genetic tools available, including analysis of mitochondrial DNA (mtDNA) sequences (e.g. COI or other suitable mtDNA genes) and appropriate nuclear DNA markers (e.g. microsatellites, single nucleotide polymorphisms), environmental DNA (eDNA) techniques and microbial metagenomics. When used in concert with traditional biological survey techniques, these tools can help to identify species, assess the genetic connectivity among populations and assess the diversity of communities. How these techniques can be applied to set-aside decision making is discussed and recommendations are made for the genetic characteristics of set-aside sites. A checklist for environmental regulators forms a guide to aid decision making on the suitability of set-aside design and assessment using genetic tools. This non-technical primer document represents the views of participants in the VentBase 2014 workshop.

Fecundity and reproductive strategies in deep-sea incirrate octopuses (Cephalopoda: Octopoda).

Coleoid cephalopods show flexibility in their reproductive strategies or mode of spawning, which can range from simultaneous terminal spawning over a short period at the end of the animal’s life to continuous spawning over a long period of the animal’s life. Although a simultaneous terminal spawning strategy is typical of shallow water temperate octopuses, it is not known whether deep-sea octopods would have the same reproductive strategy. The reproductive strategies and fecundity were investigated in nine species of deep-sea incirrate octopuses: Bathypolypus arcticus, Bathypolypus bairdii, Bathypolypus ergasticus, Bathypolypus sponsalis, Bathypolypus valdiviae, Benthoctopus levis, Benthoctopus normani, Benthoctopus sp., and Graneledone verrucosa (total n = 85). Egg-length frequency graphs and multivariate analysis (principal components analysis) suggest that B. sponsalis has a synchronous ovulation pattern and therefore a simultaneous terminal spawning strategy. Although a simultaneous terminal spawning strategy is most likely for B. levis and B. normani, the egg-length frequency graphs and multivariate analysis also suggest a greater variation in egglengths which could lead to spawning over an extended period.

Redescription of the deep-sea octopod Benthoctopus normani (Massy 1907) and a description of a new species from the Northeast Atlantic

A long-synonymized species Benthoctopus normani (Massy 1907) (Cephalopoda: Octopodidae) is redescribed from material collected over 30 years by the National Oceanography Centre, Southampton and the National Museums of Scotland. It can be distinguished from other octopodid specimens found in deep waters of the Northeast Atlantic by its biserial suckers, lack of ink sac, and simple ligula, which lacks transverse ridges. Examination of the collections led to the identification of a new species of Benthoctopus from the Northeast Atlantic, which is described herein.

The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses

Understanding how environmental forcing has generated and maintained large-scale patterns of biodiversity is a key goal of evolutionary research and critical to predicting the impacts of global climate change. We suggest that the initiation of the global thermohaline circulation provided a mechanism for the radiation of Southern Ocean fauna into the deep sea. We test this hypothesis using a relaxed phylogenetic approach to coestimate phylogeny and divergence times for a lineage of octopuses with Antarctic and deep-sea representatives. We show that the deep-sea lineage had their evolutionary origins in Antarctica, and estimate that this lineage diverged around 33?million years ago (Ma) and subsequently radiated at 15?Ma. Both of these dates are critical in development of the thermohaline circulation and we suggest that this has acted as an evolutionary driver enabling the Southern Ocean to become a centre of origin for deep-sea fauna. This is the first unequivocal molecular evidence that deep-sea fauna from other ocean basins originated from Southern Ocean taxa and this is the first evidence to be dated.

Parasitic foraminifers on a deep-sea chiton (Mollusca, Polyplacophora, Leptochitonidae) from Iceland

Epibiotic foraminifers selectively settle on the most food-rich area of the host substrate, even when the species acts as a facultative ectoparasite in later life stages. In 398 specimens examined of the deep-sea chiton Leptochiton arcticus from Iceland, 46% show evidence of infestation by foraminifers, with many showing extensive shell damage from present and past bioeroding epibionts. Disturbances to the inner layer of the host shell are indicative of parasitism, as evidenced both by wound healing calcification and protrusions of the foraminiferan tubules. The epibionts employ different feeding strategies at different stages of their life cycle, taking advantage of nutrient availability from the posterior respiration currents and excrement of the chitons as juveniles, and feeding parasitically as adults. Epibiont persistence on individual hosts-through successive generations, or long-term continuous bioerosion by epibionts-allow larger adult parasitic foraminifers of Hyrrokkin sarcophaga to penetrate the thick tail valve of a chiton and feed parasitically on the host tissue. The proportion of chitons infested increases with host size, indicating that epibionts are accumulated through a chiton's life, seemingly without major detriment to host survivorship.

The deep-sea chiton Nierstraszella (Mollusca: Polyplacophora: Lepidopleurida) in the Indo-West Pacific: taxonomy, morphology and a bizarre ectosymbiont

This study investigated the taxonomy and distribution of the deep-sea polyplacophoran mollusc Nierstraszella Sirenko, 1992 in the Indo-West Pacific, based on a collection of 516 specimens collected in the Philippines and Solomon Islands. Although seven species names have historically been proposed in this group of chitons, all have been considered as synonyms of the monotypic N. lineata (Nierstrasz, 1905). Morphological examination of this new material reveals the presence of two species. N. lineata is distinct from N. andamanica (Smith, 1906), based on morphological characters given in the original species description and very distinctly different morphology of aesthete pores in the shell surface. Furthermore, populations of N. andamanica in the Philippines and Solomon Islands are locally colonized with the epibiotic (ectoparasitic) bryozoan Pseudobathyalozoon profundum d'Hondt, 2006. These bryozoans attach ventrally to the girdle of the host chiton and the erect zooids feed within the pallial cavity, among the chiton's gills.

Scarred limpets at hydrothermal vents: evidence of predation by deep-sea whelks

The chaotic physical and chemical environment at deep-sea hydrothermal vents has been associated with an ecosystem with few predators, arguably allowing the habitat to provide refuge for vulnerable species. The dominance of endemic limpets with thin, open-coiled shells at north Pacific vents may support this view. To test their vulnerability to predation, the incidence of healed repair scars, which are argued to reflect non-lethal encounters with predators, were examined on the shells of over 5,800 vent limpets of Lepetodrilus fucensis McLean (1988) that were collected from 13 to 18 August 1996. Three vent fields on the Juan de Fuca Ridge at ca. 2,200 m depth were sampled, two within 70 m of 47 degrees 56.87'N 129 degrees 05.91'W, and one at 47 degrees 57.85'N 129 degrees 05.15'W with the conspicuous potential limpet predators, the zoarcid fish Pachycara gymninium Anderson and Peden (1988), the galatheid crab Munidopsis alvisca Williams (1988), and the buccinid snail Buccinum thermophilum Harasewych and Kantor (2002). Limpets from the predator-rich vent were most often scarred, a significant difference created by the high incidence of scars on small (

Evolution in the deep sea: a combined analysis of the earliest diverging living chitons (Mollusca : Polyplacophora : Lepidopleurida)

Lepidopleurida is the earliest diverged group of living polyplacophoran molluscs. They are found predominantly in the deep sea, including sunken wood, cold seeps, other abyssal habitats, and a few species are found in shallow water. The group is morphologically identified by anatomical features of their gills, sensory aesthetes, and gametes. Their shell features closely resemble the oldest fossils that can be identified as modern polyplacophorans. We present the first molecular phylogenetic study of this group, and also the first combined phylogenetic analysis for any chiton, including three gene regions and 69 morphological characters. The results show that Lepidopleurida is unambiguously monophyletic, and the nine genera fall into five distinct clades, which partly support the current view of polyplacophoran taxonomy. The genus Hanleyella Sirenko, 1973 is included in the family Protochitonidae, and Ferreiraellidae constitutes another distinct clade. The large cosmopolitan genus Leptochiton Gray, 1847 is not monophyletic; Leptochiton and Leptochitonidae sensu stricto are restricted to North Atlantic and Mediterranean taxa. Leptochitonidae s. str. is sister to Protochitonidae. The results also suggest two separate clades independently inhabiting sunken wood substrates in the south-west Pacific. Antarctic and other chemosynthetic-dwelling species may be derived from wood-living species. Substantial taxonomic revision remains to be done to resolve lepidopleuran classification, but the phylogeny presented here is a dramatic step forward in clarifying the relationships within this interesting group.

Holothurians – potential biomonitors for metal levels in deep-sea sediments

Levels of cadmium, copper, aluminium, iron, manganese and zinc (Cd, Cu, Al, Fe, Mn and Zn) in deep-sea sediments and sediment-feeding holothurians are reported. Profiles of metals were found to vary with depth in the sediment. Holothurian foregut metal values are generally closer to surficial sediment levels, whereas body wall levels, with the exception of Cd and Cu, were generally lower. Holothurians are presented as potential biomonitors of metal concentrations in the deep-sea floor environment.

Prokaryotes on the tentacles of deep-sea holothurians: A novel form of dietary supplementation

Bathyal and abyssal epibenthic holothurians have a layer of bacteria lying over the tentacular epidermis and below the cuticle. Thus the tentacles of deep-sea holothurians may provide ideal conditions for subcuticular bacteria. These bacteria appear to be regulated by phagocytosis, which, together with pinocytosis would facilitate transfer of bacterial metabolites to the holothurian. Their abundance suggests a previously unknown pathway for energy transformation and assimilation of particular significance in an environment where food is limiting.