ROLE OF ENVIRONMENTAL-TEMPERATURE IN SEASONAL-CHANGES OF FATTY-ACID COMPOSITION OF HEPATIC LIPID IN AN AIR-BREATHING INDIAN TELEOST, CHANNA-PUNCTATUS (BLOCH)

Fatty acid composition of hepatic total lipids and phospholipids of an Indian air-breathing fish, Channa punctatus Bloch, collected in summer (32.degree. C) or in winter (16.degree. C) or after exposing summer and winter adapted fish to the opposite temperatures for 1 mo. was investigated. DPH [diphenylhexatriene] fluorescence polarization of phospholipid vesicles was also monitored. There was a tendency to accumulate eicosa- and docosapolyenoic fatty acids to the expense of monoenoic acids in the winter fish livers. This tendency was not so clear in the case of isolated phospholipids. Summer adapted fish acclimated to 16.degree. C contained significantly more docosapolyenoic acids in their phospholipids than winter adapted fish acclimated to 32.degree. C. Phospholipid vesicles obtained from summer adapted fish livers proved to be more rigid than those from winter adapted ones. Fluorescence polarization vs. 1/T plots revealed 2 breaks indicating phase separations at 25 and 15.degree. C, respectively. No such breaks were evident with phospholipids obtained from winter adapted fish. When winter adapted fish were acclimated to 32.degree. C the fluidity of vesicles, including the appearance of phase separation temperatures, become very similar to the summer adapted fish suggesting a complete adaptation of membrane physical state to temperature. Exposing summer adapted fish to 16.degree. C resulted in the disappearance of phase separation temperatures observed at 32.degree. C but these vesicles still exhibited higher polarization values. For the complete adaptation of membrane physical state to temperature in warm adapted 16.degree. C acclimated fish, some factors other than phospholipid fatty acid composition are required.