If you are experiencing problems downloading PDF or HTML fulltext, our helpdesk recommend clearing your browser cache and trying again. If you need help in clearing your cache, please click here . Still need help? Email firstname.lastname@example.org
Several features of the proboscis morphology of Mitra catalinae Dall are unique among the known species of mitrid gastropods. These features include (1) a bilayered ring of comparatively large (7 μm high × 11 μm wide) squamous cells located midway along
the length of the peristomial rim, (2) a pair of concentrically arranged cone-shaped buccal lips projecting into the peristomial rim, (3) a muscular esophagus lacking a well-developed secretory epithelium, and (4) a small pyriform epiproboscis consisting of longitudinal and transverse muscle
fibers. It is proposed that the epiproboscis and the buccal lips regulate the movement of coelomic fluid and buoyant materials (e.g., eggs) from the sipunculan prey into the snail's alimentary tract by acting as a pump or as a valve. A hydrostatic mechansim appears to effect protraction of
the epiproboscis. Comparison of the morphologies and functions of mitrid epiproboscides suggest that the epiproboscis developed from the musculature of the buccal mass, and the epipropboscis sheaths were derived from the walls of the buccal cavity. The mitrid epiproboscis shows structural
and functional affinities with most of the other kinds of molluscan subradular organs. An evolutionary sequence of the mitrid epiproboscis is proposed in which the epiproboscis of M. catalinae is regarded as similar to a form ancestral to other modem mitrid epiproboscides.
The Bulletin of Marine Science is dedicated to the dissemination of high quality research from the world's oceans. All aspects of marine science are treated by the Bulletin of Marine Science, including papers in marine biology, biological oceanography, fisheries, marine affairs, applied marine physics, marine geology and geophysics, marine and atmospheric chemistry, and meteorology and physical oceanography.