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.

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.

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.

Numerical simulation of a patent technology for sealing of deep-sea oil wells using nonlinear finite element method

For over 50 years bridge plugs and cement have been used for well abandonment and work over and are still the material of choice. However the failures of cement abandonments using bridge plugs has been reported on many occasions, some of which have resulted in fatal consequences. A new patented product is designed to address the shortcomings associated with using bridge plugs and cement. The new developed tools use an alloy based on bismuth that is melted in situ using Thermite reaction. The tool uses the expansion properties of bismuth to seal the well. Testing the new technology in real field under more than 2 km deep sea water can be expensive. Virtual simulation of the new device under simulated thermal and mechanical environment can be achieved using nonlinear finite element method to validate the product and reduce cost. Experimental testing in the lab is performed to measure heat generated due to thermite reaction. Then, a sequential thermal mechanical explicit/implicit finite element solver is used to simulate the device under both testing lab and deep water conditions.

Microbial community of the deep-sea brine Lake Kryos seawater-brine interface is active below the chaotropicity limit of life as revealed by recovery of mRNA

Within the complex of deep, hypersaline anoxic lakes (DHALs) of the Mediterranean Ridge, we identified a new, unexplored DHAL and named it ‘Lake Kryos’ after a nearby depression. This lake is filled with magnesium chloride (MgCl2)-rich, athalassohaline brine (salinity > 470 practical salinity units), presumably formed by the dissolution of Messinian bischofite. Compared with the DHAL Discovery, it contains elevated concentrations of kosmotropic sodium and sulfate ions, which are capable of reducing the net chaotropicily of MgCl2-rich solutions. The brine of Lake Kryos may therefore be biologically permissive at MgCl2 concentrations previously considered incompatible with life. We characterized the microbiology of the seawater–Kryos brine interface and managed to recover mRNA from the 2.27–3.03 MMgCl2 layer (equivalent to 0.747–0.631 water activity), thereby expanding the established chaotropicity window-for-life. The primary bacterial taxa present there were Kebrit Deep Bacteria 1 candidate division and DHAL-specific group of organisms, distantly related toDesulfohalobium. Two euryarchaeal candidate divisions, Mediterranean Sea Brine Lakes group 1 and halophilic cluster 1, accounted for > 85% of the rRNA-containing archaeal clones derived from the 2.27–3.03 M MgCl2 layer, but were minority community-members in the overlying interface-layers. These findings shed light on the plausibility of life in highly chaotropic environments, geochemical windows for microbial extremophiles, and have implications for habitability elsewhere in the Solar System.