HISTOLOGICAL CHARACTERISTICS OF THE FOOT AND LOCOMOTORY ACTIVITY OF CREPIDULA-DILATATA LAMARCK (GASTROPODA, CALYPTRAEIDAE) IN RELATION TO SEX-CHANGES

Crepidula dilatata Lamarck individuals can be categorized into one of the following sexual states: immature (up to 8.5 mm shell length), mal e (7.5-19.0 mm), intersex (11.5-19.9 mm) or female (over 17.3 mm). His tological analysis of the gonads shows protandry in this species. The locomotory activity of these animals diminishes from active movement i n the early stages, juveniles, and males to a strong sessile condition in females. This is related to reproductive mechanisms which involve copulation, benthic capsules and parental care. Histological analysis of the foot shows prevalence of three types of epithelial mucocytes in motile animals. A fourth type of mucocyte (M4) is present in higher a bundance in sessile females and is associated with a greater adhesive capacity of the foot for the substrate. Predominance of smooth muscle bundles in the foot of younger animals will also facilitate locomotion . Older, sessile animals have thick columellar muscles, possibly assoc iated with the need to lift the shell up for ventilation and feeding. (C) 1998 Elsevier Science B.V.