Reproduction in the Aggregating Sea Anemone, Anthopleura elegantissima

Abstract

From a sample of 240 specimens of the aggregating sea anemone, Anthopleura elegantissima, collected a few miles north of the Golden Gate, males and females were shown to be distributed as unisexual aggregations on the rocks. The degree of gonadal development was measured by taking the gonad index (the ratio of volume of gonads to wet weight of anemone) every month for nearly 2 years (1959 and 1960) . This showed an annual reproductive cycle, beginning in late fall or winter, and culminating in complete spawning of the population in late September. Measurements of ovarian egg size during 1959 and 1960 corresponded well with the cycle as expressed by the gonad index. Male and female cycles were not directly comparable on the basis of the gonad index, but identifiable males were observed over nearly the same periods as females, producing tailed sperm during the time when ovarian eggs were near their maximum size, and spawning at the same time.