Premieres observations sur la meiofaune des sites hydrothermaux de la dorsale Est-Pacifique (Guaymas, 21 degree N) et de l'Explorer Ridge

The main characteristics of the meiofauna collected at three hydrothermal sites of the East Pacific Rise and Explorer Ridge are presented. Few differences are observed among the populations of the different areas, which are basically composed of nematodes, siphonostomes, poecilostomes and harpacticoid copepods, ostracods and macrofaunal juveniles (polychaetes and limpets). The Guaymas Basin meiofauna is patchily distributed and species composition varies according to the pattern of flux of hydrothermal fluid through the soft sediments. Measurements of the physico-chemical variability on the vent waters encountered of Explorer Ridge illustrate that very few meiofaunal species are adapted to H sub(2)S-rich and hot environments.