THE EFFECTS OF HYPOXIA, ALKALINITY AND NEUROCHEMICALS ON HATCHING OF ATLANTIC SALMON (SALMO-SALAR) EGGS

The hatching process of eggs from Atlantic salmon was investigated. Salmon eggs were subjected to hypoxia under different alkaline conditions in the laboratory using different buffers in the test systems. Hypoxia was a highly effective inducer of hatching in mature salmon eggs (2 days before natural hatching at 5-7°C), causing 100% hatching within 2 h of application at physiological pH. Salmon eggs were also induced to hatch by hypoxia 2-3 weeks ahead of normal hatching, but hatching occurred more slowly and asynchronously than in mature eggs and was not complete (86%). However, in this situation the induction of salmon egg hatching by hypoxia was greatly facilitated at alkaline pH. Hypoxia induced hatching only when applied less than 1 month prior to normal hatching, i.e. after ca. 300 day degrees (dC) of development. Under normoxic and physiological pH conditions hatching of mature salmon eggs was induced by dopaminergic antagonists and delayed by dopaminergic agonists. Noradrenergic and serotonergic agents also induced hatching, but they apparently act through a terminal dopaminergic mechanism. The data suggest that hypoxia is involved in the natural hatching process, and that physiological signals for hatching in mature salmon eggs may involve specific neural monitors of oxygen tension. © 1990.