Sex in the tropics: Reproduction of Chthamalus malayensis Pilsbury (Class Cirripedia) at the equator

The reproduction of a key intertidal space occupier, the barnacle, Chthamalus malayensis, was examined over a 13-month period. The reproductive cycle of C. malayensis was studied at three shores (Singapore, east and west coast of Malaysia) near the centre of its geographical range. Testes, vesiculae seminales, ovaries and embryos were scored for their stages of development. Although, in general, C. malayensis contained gonads throughout the year, the timing and level of peak development varied between the three shores. Embryos were present throughout the year in west Malaysia but were absent for 4-5 months in east Malaysia (June-August and October) and Singapore (February, April and August). Variations in the reproductive cycles and brooding were not clearly linked to the timing of monsoons. The lack of seasonal peaks in breeding may be attributed to the relatively constant climatic conditions experienced near the equator.