Crepidula argentina (Gastropoda : Calyptraeidae), a new species from the littoral of Argentina

Crepidula argentina, a new species of gastropod of the family Calyptraeidae , is described from the littoral of Mar del Plata, province of Buenos Aires , Argentina. The new species is chologically similar to C. protea d'Orbigny from southern Brazil. Crepidula argentina has a larger, subcircular shell and lower convexity than C. protea. Anatomical characters that allow differ entiation from this latter species are: larger lateral shell muscle and ver y weak dorsal shell muscle; kidney proportionally smaller, with a character istic arrangement of inner folds of dorsal lobe; presence of a renal vessel edging rectum and working as adrectal sinus; connection between odontophor e muscle pairs m7 and mil; longer salivary gland; four ducts to digestive g land in stomach (instead of two); distinctive arrangement of folds in inner surface of stomach between esophageal aperture and posterior pair of ducts to digestive gland; seminal Vesicle of males broad and few coiled; penis a nd papilla long and narrow; vaginal tube running closely attached to capsul e gland. The reproductive biology is also distinctive. Crepidula argentina new species has a very well defined seasonal reproductive cycle. Females br ood between 1 and 46 egg capsules per spawn. The average total number of em bryos per spawn is 5600. The uncleaved, laid egg diameter is 170 mum and th e number of eggs per egg capsule is about 320. All eggs develop, there are no nurse eggs. Larvae hatch as planktotrophic veligers. The new species is compared with other members of the genus Crepidula from the southern Atlant ic coast of South America.