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Authors used photogrammetric and videogrammetric data collected at 13 degree N/EPR by the French manned submersible Cyana during the Biocyatherm and Biocyarise cruises to estimate the biomass of vent fauna. Two distinct faunal assemblages are associated with low- and high-temperature vents, Vestimentifera. The former, characterized by giant tube worms and bivalves, the latter by the so-called "Pompeii worms" (Alvinellidae). The cold vent biomass may reach 8.5 kg m super(2), far in excess of the hot vent biomass which amounts to 2.4 kg. Such a difference is linked to higher integrated symbiosis between primary and secondary producers in cold vent assemblages, hot vent secondary production being dependent upon separate ingestion/digestion processes.

Several unknown animal forms have recently been collected in the immediate vicinity of hot hydrothermal vents in the Eastern Pacific Ocean, forming a flourishing community of organisms. A tubicolous polychaete builds parchment like tubes around some of the hydrothermal vents. The tubes are covered with particles of metallic sulfur. This annelid is a new species, and is called Alvinella pompejana, new genus and species. The new sub-family Alvinellinae, erected to contain this new species, can be included in the family Ampharetidae (order Terebellida), in spite of several aberrant features. In addition to its morphological and taxonomic peculiarities. Alvinella pompejana also exhibits some remarkable biological features, in particular the existence of two successive ontogenetic States. The youngest may ensure species propagation by accidental or normal autotomy. [NOT CONTROLLED OCR], A proximité immédiate des sources hydrothermales chaudes découvertes dans l'est du Pacifique, ont été récoltées diverses formes animales souvent inconnues, et constituant une communauté exubérante. Parmi elles, une annélide polychète tubicole construit ses tubes parcheminés recouverts de particules de sulfures métalliques, autour de certaines sources hydrothermales. Cette annélide appartient à une espèce nouvelle, Alvinella pompejana gen. sp. nov. La sous-famille nouvelle des Alvinellinae, créée pour renfermer cette forme nouvelle, peut être rangée, malgré l'existence de plusieurs caractères aberrants, dans la famille des Ampharetidae (ordre des Terebellida). Outre ses particularités morphologiques et systématiques, Alvinella pompejana présente de remarquables traits biologiques, en particulier l'existence de deux stades ontogéniques successifs, dont le plus jeune assure vraisemblablement la propagation de l'espèce par autotomie accidentelle ou naturelle. [OCR NON CONTRÔLE]