Changes in structure and fertilizing ability of marine and preshwater fish spermatozoa diluted in media of various salinities

Abstract

The spermatozoa of various marine teleosts (sea bass, Dicentrarchus labrax; sea bream, Sparus auratus) or fresh water teleosts (trout, Salmo gairdneri; pike, Esox lucius; guppy, Poecilia reticulata) were diluted in media of different salinities. Motility, morphological changes and fertilizing ability were the criteria used in judging the effects of such treatments. The medium best adapted to dilution of sea-fish sperm had a salinity of about 20‰. Sperm motility was increased and prolonged, and fertilization rate was significantly improved ( P<0.05) for the sea bass at a 1 1000 dilution. For freshwater fish (trout and pike), an extender with about 7‰ salinity increased motility time and fertility ability ( P<0.01) as compared to freshwater. After dilution in fresh water the structure of trout spermatozoa was considerably altered (rupture of plasma membrane and mitochondrial swelling). When spermatozoa were diluted in the extender, there were no significant structural changes in trout, but alteration occurred in the mid-piece of the guppy spermatozoon. It is concluded that fresh water or sea water are not the best media for the practice of artificial insemination in freshwater or marine fish. Investigations should be carried out to define the best extender for use in techniques of artificial insemination in fish produced in aquaculture.