Circulation of hemocoelic fluid during slow and fast swimming in the pteropod mollusc Clione limacina

In the pteropod mollusc Clione limacina Phipps 1774, individuals possess an open circulatory system that fills their body cavities and functions as a hydrostatic skeleton. Individuals of C. limacina demonstrate two distinct swimming behaviors, slow and fast swimming, and their wings are supported by their hydrostatic skeleton. We investigated the circulation of fluid within the body cavities of individuals of C. limacina by injecting dye into the hemocoelic compartments to visualize flow during both slow swimming and serotonin-induced fast swimming. Hemocoelic fluid was observed to have a defined pattern of flow: rostrally from the heart into the wings and head, then following a dorsal pathway caudally into the body and tail before being taken up by the heart again. During patterned attack behavior, the neck constricted in width as the head's buccal cones were hydraulically inflated with hemocoelic fluid.