TEMPERATURE AS A KEY FACTOR DETERMINING THE REGIONAL VARIABILITY OF THE XENOBIOTIC-INDUCIBLE ETHOXYRESORUFIN-O-DEETHYLASE ACTIVITY IN THE LIVER OF DAB (LIMANDA-LIMANDA)

Water temperature exhibits a strong influence on the regional variabil ity in activity of the 7-ethoxyresorufin-O-deethylase (EROD) in the li ver of dab (Limanda limanda) from the German Eight during the spawning and postspawning seasons. The relationship between EROD activity and water temperature found in situ was, surprisingly, not masked by migra tions of dab. Correlations between EROD activity and temperature could not be explained by a direct temperature effect in terms of temperatu re compensation. Instead, we suppose that temperature influences EROD activity indirectly via its influence on the duration of the gonadal c ycle and thus on the time of spawning, which we assume to be coupled w ith the seasonal variation in EROD activity. Significant negative corr elations between EROD activity and the condition factor, gonadosomatic index, and liver-length index could be attributed to the parallel or opposite temporal changes of these parameters. In the liver of spawnin g females, no linear relationship was detected between the EROD activi ty and the concentration of the polychlorinated biphenyls (PCB), which have been previously determined.