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Abstract: Marine molluscs are subjected to constant microbial threats in their natural habitats. As a result, they represent suitable models for the study of the molecular mechanisms that govern defense reactions in marine organisms. To understand humoral and cellular defense reactions in animals defying extreme physical and chemical conditions we set out to investigate the deep sea hydrothermal vent mussel Bathymodiolus azoricus found in abundance at the Mid-Atlantic Ridge. In the present study, hemocytes were stimulated with compounds of microbial origin and cellular morphological alterations as well as the production of superoxide assessed. Consequently, zymosan, glucan and peptidoglycan were considered as potent inducers of cellular reactions for inducing drastic cell morphology changes and high levels of superoxide production. Furthermore, we have presented for the first time in a deep sea hydrothermal vent animal, molecular evidence of the Rel-homology domain, a conserved motif present in all members of the Rel/nuclear-factor NF-κB family. Additionally we have demonstrated the occurrence of the antibacterial gene mytilin in Bathymodiolus azoricus gill tissues. Our results support the premise of an evolutionary conserved innate immune system in Bathymodiolus. Such system is seemingly homologous to that of Insects and other Bivalves and may involve the participation of NF-κB transcription factors and antibacterial genes. [Copyright &y& Elsevier]

Paucity of data on population structure and connectivity in deep sea species remains a major obstacle to their sustainable management and conservation in the face of ever increasing fisheries pressure and other forms of impacts on deep sea ecosystems. The roughhead grenadier Macrourus berglax presents all the classical characteristics of a deep sea species, such as slow growth and low fecundity, which make them particularly vulnerable to anthropogenic impact, due to their low resilience to change. In this study, the population structure of the roughhead grenadier is investigated throughout its geographic distribution using two sets of molecular markers: a partial sequence of the Control Region of mitochondrial DNA and species-specific microsatellites. No evidence of significant structure was found throughout the North Atlantic, with both sets of molecular markers yielding the same results of overall homogeneity. We posit two non-mutually exclusive scenarios that can explain such outcome: i) substantial high gene flow among locations, possibly maintained by larval stages, ii) very large effective size of post-glacially expanded populations. The results can inform management strategies in this by-caught species, and contribute to the broader issue of biological connectivity in the deep ocean. [ABSTRACT FROM AUTHOR]

Many fish species are well-known obligatory inhabitants of shallow-water tropical coral reefs but such associations are difficult to study in deep-water environments. We address the association between two deep-sea fish with low mobility and large sessile invertebrates using a compilation of 20 years of unpublished in situ observations. Data were collected on Northeast Atlantic (NEA) island slopes and seamounts, from the Azores to the Canary Islands, comprising 127 new records of the circalittoral Labridae Lappanella fasciata and 15 of the upper bathyal Ophiididae Benthocometes robustus . Observations by divers, remote operated vehicles (ROV SP, Luso, Victor, Falcon Seaeye ), towed vehicles (Greenpeace) and manned submersibles ( LULA, Nautile ) validated the species association to cold water corals (CWC) and large hydrozoans. L. fasciata occurred from lower infralittoral (41 m) throughout the circalittoral, down to the upper bathyal at 398 m depth. Smaller fishes (< 10 cm) tend to form larger schools up to five individuals, with larger fishes (10–15 cm) occurring alone or in smaller groups at greater depths. The labrids favoured areas with large sessile invertebrates (> 10 cm) occurring at < 1 body-length, swimming inside or in close vicinity to the tallest and most complex three-dimensional structure in the field of observation. These included hydrozoans ( Polyplumaria flabellata , Nemertesia antennina ), CWC (e.g. Antipathella wollastoni , Acanthogorgia armata, Stichopathes sp.), and less frequently sponges (e.g. Pseudotrachya hystrix ). B. robustus presented a coral-cryptic behavior, being recorded in the bathyal zone between 350 and 734 m depth, always inside CWC (e.g. Acanthogorgia spp., Antipathella spp., Callogorgia verticillata , Dendrophyllia alternata, Leiopathes spp.), and remaining within the coral branching. B. robustus were collected with baited traps providing biological information and dietary information reinforcing the trophic linkage between the CWC habitat and this predator. Gathered evidence renders CWC and hydroid gardens as Essential Fish Habitats for both species, being therefore sensitive to environmental and anthropogenic impacts on these Vulnerable Marine Ecosystems. The Mediterranean distribution of L. fasciata is extended to NEA seamounts and island slopes and the amphi-Atlantic distribution of B. robustus is bridged with molecular data support. Both species are expected to occur throughout the Macaronesia and Mediterranean island slopes and shallow seamounts on habitats with large sessile invertebrates. [ABSTRACT FROM AUTHOR]