Phosphorus metabolism and water uptake during final maturation of ovaries of teleosts with pelagic and demersal eggs

Abstract

An earlier study showed large changes in ovarian phosphoprotein, a characteristic component of vertebrate yolk, during post-vitellogenic meiotic maturation (ripening) of ovaries of teleosts with pelagic eggs. Here, the study of four phosphorus-containing ovarian fractions is extended to other teleost families with pelagic eggs and to species with demersal eggs. Fishes were caught in the sea and lakes of western Scotland between 1982 and 1984. In the codGadus morhua, spratSprattus sprattus, dragonetCallionymus lyra, Norway poutTrisopterus esmarkii, saithePollachius virens, lingMolva molva and flounderPlatichthys flesus, all of which spawn pelagic eggs, the massive water influx during ripening which renders the eggs buoyant was accompanied by large changes in yolk phosphoprotein which were apparent as decrease or disappearance of protein phosphorus as conventionally determined. During ripening of the demersal eggs of the herringClupea harengus, both the water uptake and the decrease in protein phosphorus were less pronounced. In the three-spined sticklebackGasterosteus aculeatus, sea sticklebackSpinachia spinachia, sand gobyPomatoschistus minutus and perchPerca fluviatilis, little or no changes in water content or protein phosphorus both usually increased in species with pronounced water uptake and decreased in species with little or no water uptake. Lipid phosphorus showed little change in all species examined except herring, in which it increased. It is concluded that the characteristic changes in phosphoprotein and other phosphorus-containing fractions are most pronounced in species with pelagic eggs exhibiting massive water uptake on ripening, but are found to a lesser extent in species with demersal eggs in which considerable water uptake accompanies ripening.