THE ECOLOGY OF PATELLA LINNAEUS FROM THE CAPE PENINSULA, SOUTH AFRICA. 2. REPRODUCTIVE CYCLES.

Summary

The gonad structure and cycles of seven Patella spp. are described. Most spawn once a year. P. cochlear, P. argenvillei, P. barbara, P. granatina and P. granularis are autumn to winter breeders spawning in May-June. P. oculus spawns in September and P. longicosta in October-November. Partial spawning was recorded for P. cochlear, prior to the attainment of maximum maturity. In P. oculus a false spawning of a small percentage of females occurred in May and biannual spawning is possible.

Spawning time is related to distribution. Autumn and winter breeders occur on the cold west coast and may also occur on the warmer coasts. Spring and summer breeders are restricted to warm waters. The role of sea temperatures in limiting larval dispersal is discussed.

Gonad maturation is related to decreasing temperatures, but spawning may be stimulated by a different factor.

The output of eggs in all species was in the region of 500 x 10³ eggs per gram of ovary. With the exception of P. granatina and P. oculus, the weight of gamete output was greater in males. Males were also numerically predominant in all species except P. barbara, and the sex ratio may be correlated with the mean density of populations. The mean size of males is less than females, and they mature sexually at a smaller size. This may be because more energy is channelled into gonad growth in the males, at the expense of somatic growth. High gamete output occurs in species with high growth-rates and low generation time.

P. oculus is the only South African species displaying protandric hermaphroditism.