A unusual pinnotherid zoea attributed to Afropinnotheres monodi Manning, 1993 (Decapoda: Brachyura: Pinnotheridea) from the Selvagens Islands (Eastern Atlantic Ocean)

A pinnotherid zoea taken in a plankton sample from the Selvagens Islands during the TFMCBM/SELVAGENS’2000 Cruise, organized by the Natural Sciences Museum of Tenerife (Canary Islands), differs from previously described zoeas of the family. The specimen has dorsal and lateral spines but no rostrum, a combination of characters not previously described from pinnotherid zoeas. The lateral spines originate behind the upper part of the eye, unlike all previously described Pinnotheridae zoeas where these spines, when present, originate near the ventrolateral margin of the carapace. The specimen is attributed to Afropinnotheres monodi, the only pinnotherid species known from the area with undescribed larvae.

Food sources, behaviour, and distribution of hydrothermal vent shrimps at the Mid-Atlantic Ridge

Five species of bresilioid shrimp were investigated at seven hydrothermal sites on the Mid-Atlantic Ridge: Menez Gwen, Lucky Strike, Rainbow, Broken Spur, TAG, Snake Pit and Logatchev. Samples were prepared for analysis of stable isotopes, elemental composition and lipids. Shrimp behaviour was observed from the submersible ‘Alvin’ and in the laboratory aboard RV ‘Atlantis’. The distribution and zonation of the shrimp species was recorded. Juvenile shrimp of all species arrive at the vents carrying reserves of photosynthetic origin, built-up in the pelagic larval stages. These reserves are used while the shrimp metamorphose to the adult form and, in Rimicaris exoculata and Chorocaris chacei, while they develop epibiotic bacteria supporting structures, the modified mouthparts and the inside of the carapace. The main food of adult R. exoculata is filamentous bacteria that grow on these structures. The intermediate sizes of C. chacei also feed on such bacteria, but the final stage gets some food by scavenging or predation. Mirocaris species scavenge diverse sources; they are not trophically dependent on either R. exoculata or mussels. Adults of Alvinocaris markensis are predators of other vent animals, including R. exoculata. The dense swarms of R. exoculata, with their exosymbionts, can be compared to endosymbiont-containing animals such as Bathymodiolus and the vestimentiferan tube-worms of the Pacific vents. Such associations, whether endo- or ectosymbiotic, may be necessary for the development of flourishing communities at hydrothermal vents.