Relationships between seasonal biochemical changes and the reproductive cycle of the intertidal gastropod Thais lamellosa Gmelin (Gastropoda, Prosobranchia).

The seasonal variation in the major biochemical constituents of T. lamellosa Gmelin have been studied in relation to the reproductive cycle. Digestive gland, foot muscle and gonad were analysed for protein, glycogen, lipid and ash over a period of one year. In addition to biochemical analyses, histological sections of digestive gland and gonad were made throughout the same period. Histological data supplied information on feeding and gamete maturation. Two major periods of feeding activity occurred in April and August. Gametogenesis began in late summer and the peak spawning period was in March. Glycogen is at a maximum in the digestive gland at times of maximum feeding, but food is stored in the digestive gland in the form of lipid. Stored lipid is utilized by the animal during the winter. Glycogen is at a low level in all tissues and appears to be used primarily for lipid and yolk synthesis. The foot muscle does not store either lipid or glycogen to any appreciable extent. Under normal field conditions during the winter, the digestive gland index decreases as reserves are utilized, while the gonad size is maintained until spawning. Animals which are maintained through the same period under artificial summer conditions, show no loss in the digestive gland index, but a decrease in the size of the gonad. None of the oogonia reach maturity and the mature oocytes are resorbed. The starved animals resorb more material from the gonad than fed animals. The possible role of environmental factors in controlling reproduction is discussed.Science, Faculty ofZoology, Department ofGraduat