Reproduction in Three Species of Intertidal Barnacles from Central California

The reproductive biology of eastern Atlantic barnacles has been studied extensively, with emphasis on the role of temperature in regulating reproduction (e.g., Crisp, 1950, 1954; Patel and Crisp, 1960a; Barnes, 1963; Barnes and Stone, 1973). However, there has been much less work on cirripedes elsewhere in the world. This paper compares the reproductive cycles and brood production of three species of intertidal barnacles abundant in central California: Chthamalus fissus Darwin, 1854; Balanus glandula Darwin, 1854; and Tetraclita squamosa rubescens Darwin, 1854 (hereafter called T. squamosa in this paper). On the west coast of N9rth America the role of barnacles in the structure of intertidal communities has be~n stressed (e.g., Connell, 1970; Dayton, 1971), but the reproductive cycles of only two intertidal and one subtidal species have received attention. Balanus glandula from British Columbia and southern California broods primarily in the cold winter and spring months but may show minor brooding activity in summer (Barnes and Barnes, 1956). On the other hand, Pollicipes polymerus has a variable reproductive cycle with a limited summer brooding season in Washington which increases in length to central California (Hilgard, 1960; Lewis, 1975), while brooding activity in southern California peaks in winter with 30% still brooding in summer (Straughan, 1971). Balanus pacificusJ a subtidal species in southern California, broods at high frequencies year-round showing no correlation with temperature (Hurley, 1973). Thus, in these species the relationship of reproduction with temperature is complex. The role of temperature or other environmental factors as proximal cues synchronizing brooding has not been studied experimentally in species of cirripedes on the west coast of North America. In this paper brooding and nutrient storage .cycles are compared in populations of the three species of barnacles occurring in the warm-water discharge canal of a large power plant and in adjacent areas of ambient temperature. Aspects of the regulation of these cycles by temperature, photoperiod, and food availability are investigated experimentally. The size and number of broods produced during a season are estimated so that the patterns of reproductive effort of these three species can be compared with other cirripedes.