DISTINCTIVE CYTOSKELETAL ORGANIZATION IN ERYTHROCYTES OF THE COLD-SEEP VESICOMYID CLAM, CALYPTOGENA-KILMERI

Erythrocytes have long served as model cells, useful for analyzing cyt oskeletal structure and function. In non-mammalian vertebrates, erythr ocytes are typically highly flattened, nucleated ellipsoids in which a marginal band (MB) of microtubules interacts with the membrane skelet on (MS) to generate and maintain cell shape. Though relatively rare, e rythrocytes also occur in representatives of many invertebrate phyla, including the arcid and vesicomyid molluscs, but the structure and fun ction of these cells are not well understood. Previous work has shown arcid erythrocytes to be highly flattened ellipsoids containing the MB -MS cytoskeletal system, similar to vertebrates but with an additional interesting feature: a functional centriole-containing centrosome ass ociated with each NIB. In the present study we have examined, for the first time, erythrocyte morphology and cytoskeletal structure in a ves icomyid. Using Calyptogena kilmeri, the dominant invertebrate at many Pacific cold seeps, we have found that the erythrocytes are only sligh tly flattened and do not contain MBs. Rather, their cytoskeletons disp lay a peripheral centriole-containing centrosome with radiating fibers , a distinctive type of organization not observed previously in mature erythrocytes from any species.