The main groups of organisms found around seafloor vents are worms , gastropods , and crustaceans , with large bivalves , and ` eyeless ' shrimp making up the bulk of non-microbial organisms . The main families of organisms found around seafloor vents are annelids , pogonophorans , gastropods , and crustaceans , with large bivalves , vestimentiferan worms , and `` eyeless '' shrimp making up the bulk of non-microbial organisms .