Enzyme polymorphism expressed in newly hatched cod larvae and genetic analysis of larvae exposed to hydrocarbons.

Cod eggs and larvae, at different stage of development, have been analyzed by starch gel electrophoresis. Four common enzymes (phosphoglucose isomerase, phosphoglucose mutase, isocitrate dehydrogenase and lactate dehydrogenase) were easily demonstrated both in eggs and larvae. Some of the isozymes present in adult fish, were expressed in newly fertilized eggs. The others, including polymorphic forms of particular interest in population studies, seemed to be activated during the process of hatching, offering the possibility to perform detailed genetic investigations at an early stage of cod larval development. Comparison between the phenotypes of parent fish and the offspring, was in complete concordance with the hypothesis of. codominant inheritance of the alleles present. The parent fish material, however, was scarce. Several groups of eggs and cod larvae were exposed to different concentrations of the sea water soluble fraction of hydrocarbons for North Sea crude oil. Unfortunately, only a few phenotypes were present in the populations. No significant changes in the genetic compositions of cod larvae were observed in the exposed populations compared to the controls. The experiments described, however, suggest a rational approach for investigating possible effects of pollutants on gene pools and genetic variability