Seasonal changes in the biochemical composition of the chiton Chiton iatricus (Polyplacophora: Mollusca) and the marine pulmonate Onchidium verruculatum (Gastropoda: Mollusca) in relation to their reproductive cycles

Seasonal changes in the biochemical composition of two molluses, gonochoric Chiton iatricus and a marine pulmonate, Ochnidium verruculatum inhabiting the same tropical area, but having different modes of reproduction, were studied. Protein is the major biochemical component stored in C. iatricus, whereas lipid is predominantly stored in O. verruculatum. The correlation between these quantifications and the annual reproductive cycles of the two species investigated suggest that nutrients stored in the somatic body parts are channeled towards the gonad during the gametogenesis. In C. iatricus sexual differences efrist in the biochemical needs of the ovary and the testis. The ovary always has a higher protein content than the testis. In the hermaphrodite pulmonate O. verruculatum, biochemical expenditure on gamete production is relatively low because this species has to spend energy on the reproductive propagation viz. copulation and egg-laying. On the contrary, in C. iatricus the biochemical energy is mainly utilized for the production of gametes which have to be produced in great numbers in order to counter-balance the loss of gametes caused by external fertilization. The collected data are discussed in the light of comparative physiology of reproduction.