Biochemical composition of seminal secretions with special reference to LDH activity in the reproductive tissues of the field crab, Paratelphusa hydrodromous (Herbst).

Biochemical composition of seminal secretions as well as the male and female reproductive tissues, with special reference to lactate dehydrogenase (LDH) activity, were determined in the field crab, Paratelphusa hydrodromous. The seminal secretions comprising spermatophores and spermatophore-carrying seminal plasma (hereafter referred to as seminal plasma) are rich in protein, free carbohydrates and lipids. The seminal plasma contains large quantities of free carbohydrates. LDH activity, as measured by UV spectrophotometric method, is very high within the spermatophores. Electrophoretic separation of LDH isozymes reveals the occurrence of 6 fractions in spermatophores, of which, the most conspicuous fraction resolves in between LDH3 and LDH4. The use of L-lactate as substrate and consideration of its relative mobility show that this fraction is homologous to the mammalian sperm-specific LDHx fraction. Among the 6 fractions, the majority of them, including LDHx, fall under M-type suggesting that they are mainly involved in the anaerobic metabolism of spermatozoa. When compared to anterior vas deferens and mid vas deferens, LDH activity is maximum in the posterior vas deferens which contains seminal secretions prior to their ejaculation. Though the LDH activity is found to be moderate in the spermathecal contents of freshly mated females, the carbohydrate reserves are very minimal. Interestingly, spermathecal contents are rich in lipid substances, thereby indicating that the spermatozoa, when stored in the spermatheca, may utilise fatty substances for oxidative metabolism.