REPRODUCTIVE HABITS AND LIFE-CYCLE OF THE SMALL CLAM KINGIELLA-CHILENICA (BIVALVIA, CYAMIIDAE) IN AN ESTUARINE SAND FLAT FROM THE SOUTH OF CHILE

A population of the small clam Kingiella chilenica Soot Ryen 1959 was studied from March 1986 to December 1988 in an intertidal flat at Queu le River, in the south of Chile. The life cycle and life history patte rn of the bivalve were established contrasting population structure an d dynamics to its reproductive habits. Individuals are gonochoristic a nd semelparous, presenting a typical annual life cycle. The species is a sequential brooder whose embryos undergo direct development. After the brooding season (summer through autumn), the adults disappear grad ually (autumn through winter). Recruited juveniles overwinter during a relatively long period. undergoing rapid growth during the spring to attain the adult stage during the summer. The number of brooded embryo s increases in proportion to adult length cubed. Life history traits o f this bivalve are compared to those reported for other small brooder clams. Some basic tendencies become apparent when traits for semelparo us versus iteroparous species are contrasted. As in other semelparous sequential brooders (Transennella tantilla, Gaimardia bahamondei), the relationship between brood size and shell length observed in K. chile nica does not fit the allometry hypothesis for marine brooding inverte brates that allometric constraints on the brooding space limit the fec undity of larger individuals. Also contrary to theoretical predictions , small body size does not limit the diversity of a clam's development al patterns. Possible explanations for this finding are discussed.