Vitamin A compounds and lipids in the blood of the Cod Gadus morhua from the Arctic, in relation to gonadal maturation

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Abstract
Cod (Gadus morhua L.) from the Arcto-Norwegian stock that spawns off northern Norway were caught at various times during the course of their gonadal maturation cycle, and plasma samples were collected for the determination of vitamin A compounds and lipids.The main changes found concerned vitamin A aldehyde, which increased from a resting level of2μg/100 ml. plasma for adult females caught in September to 10 μ/100 ml. in ripe females caught in January-March approaching their spawning grounds; by contrast little change was observed in the males. In the fish of both sexes caught in September, just prior to the onset of maturation, dehydroretinal formed about 38 % of the total aldehyde, but in the plasma of ripe females the proportion was only 16 %. In both sexes there was a fairly steady decline in the levels of vitamin A esters and alcohol in the plasma during the winter. Similarly, the concentration of plasma lipids fell during the winter in the male cod, but in the adult females, during the period of ovarian maturation, the concentration of lipids increased and was maintained at about 0·5 g/100 ml. higher than in the males; in spent fish the concentration of lipids fell to the same low levels in both sexes.It was considered that the changes in vitamin A aldehyde, and also of blood lipid, in the females were directly linked with sexual maturation, these compounds being transported to the developing eggs in the ovary. On the other hand, the general decline of vitamin A esters and alcohol in both sexes, and of lipids in the males, was probably due to the obligatory winter starvation which occurs in this stock.