Carotenoid pigments and trophic behaviour of deep-sea shrimps (Crustacea, decapoda, alvinocarididae) from a hydrothermal area of the mid-atlantic ridge.

Pigments and trophic behaviour of three species of Alvinocarididae from a Mid-Atlantic hydrothermal site were analysed. Carotenoid pigments are responsible for the more or less marked colouration of these animals. The carotenoid content of whole animals and different tissues were evaluated. Rimicaris exoculata exhibits an increased carotenoid level at the juvenile stage, while Chorocaris chacei and Alvinocaris markensis contain only few traces of pigment. Free and esterified astaxanthin, reported for most pelagic crustaceans, are present in these deep-sea shrimps. The origin of carotenoids of crustaceans living in the aphotic zone is discussed.

Stable-carbon-isotope composition of Fatty acids in hydrothermal vent mussels containing methanotrophic and thiotrophic bacterial endosymbionts.

Fatty acid biomarker analysis coupled with gas chromatography-isotope ratio mass spectrometry was used to confirm the presence of methanotrophic and thiotrophic bacterial endosymbionts in the tissues of a hydrothermal vent mussel (Bathymodiolus sp.), collected from the Menez Gwen vent field on the mid-Atlantic ridge. Monounsaturated (n-8) fatty acids, which are diagnostic of methanotrophic bacteria, were detected in all three types of tissues examined (gill, posterior adductor, and mantle), although levels were highest in gill tissues where the bacteria were found. Stable-carbon-isotope compositions (delta-C per mille relative to that of Peedee belemnite) of fatty acids for all three tissues ranged from -24.9 to -34.9 per thousand, which encompasses the range predicted for both thiotroph- and methanotroph-based nutrition. The data suggest that these thio- and methanotrophic bacterial endosymbionts are equally important in the nutrition of the vent mussel at this particular vent site.