Multiple nutritional strategies of hydrothermal vent shrimp (Rimicaris hybisae) assemblages at the Mid-Cayman Rise

Alvinocaridid shrimp occurring in dense assemblages close to vigorously venting orifices are characteristic of many vent fields on the Mid-Atlantic Ridge, Central Indian and Mid-Cayman Rise. Episymbiotic bacteria these exposed fluids enriched inorganic nutrients (carbon dioxide, sulfide) that, together with dissolved oxygen surrounding seawater, sustain autotrophic growth supply nourishment shrimp. Enigmatically, conspecific may also be found sparsely distributed periphery a field, where there is little visual evidence fluid flux. We tested null hypothesis that sources were identical for central (dense) peripheral assemblages, using gut content stable isotope analyses. Rimicaris hybisae sampled from at Von Damm Vent Field (Mid-Cayman Rise). Guts centrally aggregated contained white material inferred bacteria, while individuals this and/or pieces crustacean exoskeletons. C, N, S isotopic compositions muscle tissues significantly different between overlap space was found. A comparison δ 13 C 34 values contents abdominal revealed tissue composition reflects shrimp's source nourishment. Slight but elevated 15 N shrimp, exoskeleton fragments gut, suggest facultative carnivory peripherally The lower consistent mixotrophic diet. conclude R. have sources, relying episymbionts, diverse comprising Crustacea. • active venting. differed assemblages. Isotopic reflect source. rely solely episymbionts. Peripheral episymbionts partially carnivorous.