ON THE PROBLEM OF REPRODUCTIVE PRODUCTS HETEROGENEITY IN SALMONID FISH: PINK SALMON (ONCORHYNCHUS GORBUSCHA) EGGS CASE-STUDY

Abstract

The study on unfertilized eggs of pink salmon (Oncorhynchus gorbuscha, Salmonidae) was designed to determine the mechanism underlying the previously reported phenomenon of heterogeneity of salmonid embryos and early larvae in terms of the metabolic rate, locomotor activity and their particular relations with the ambient environment. In order to reveal possible maternal effects, a comparison of size parameters and the activities of proteolytic enzymes, such as lysosomal cathepsins B and D and calcium-dependent calpains, in eggs from different locations (from the front, middle and rear thirds of the ovaries of spawning O. gorbuscha females) was conducted. Earlier characterization of the fish proteolytic machinery showed an utter importance of the named enzymes in the regulation of growth and metabolic processes in unfertilized and fertilized eggs. In ourexperiment no reliable individual variability of eggs from different egg mass parts either in size or in intracellular protease activity levels was detected. The obtained results suggest that the cause for differentiation of young salmonids in physiology and morphology obvious at embryogenesis and early post-embryogenesis should be apparently searched through the genetic variability of fertilized material or its interactions with the environment but not in the difference of growth and maturation rates in fish ovaries.

Keywords

• calpains
• cathepsins
• oocytes
• ovary
• maternal effects
• o. gorbuscha.