Patterns of growth and energy allocation in northern California populations of Littorina (Gastropoda: Prosobranchia)

Abstract

Seasonal patterns in shell growth rates, tissue weights, and female reproductive efforts were monitored for three species of western North American rocky shore gastropods, Littorina keenae Rosewater (supralittoral), L. scutulata Gould (high intertidal), and L. plena Gould (high intertidal). Growth rates conformed to the Von Bertalanffy growth model. Relative to male snails, female L. keenae appeared to sacrifice shell growth to expend more energy on the production of large quantities of gametes during the spring; growth rates of females and large males were highest during autumn when microalgal food supplies were seasonally abundant. In contrast, spring tended to be the best season for shell growth of L. scutulata and L. plena; however, reproductive output was poor and sporadic for these two species, and growth rates in the field during all seasons were low compared to growth rates of snails held under laboratory conditions with abundant food. High population densities of snails at shore levels occupied by L. scutulata and L. plena may greatly reduce food levels upon which individual snails rely for growth and reproduction.