Metabolic strategy in pelagic squid of genus Sthenoteuthis (Ommastrephidae) as the basis of high abundance and productivity: An overview of the Soviet investigations

The long-term investigations of nektonic squid Sthenoteuthis pteropus and Sthenoteuthis oualaniensis (between 1978 and 1990) have revealed some special features in a metabolism of these animals. These are: (1) rate of energy expenditure is very high (coefficient 'a' in equation Q = aWk is from 3.1 to 4.7 at 26° to 30°C (more than that of other fast swimming animals); (2) hepatopancreatic index is about 4% wet body weight, twice that of actively swimming fishes; (3) protein is the main substrate for energy metabolism; (4) the polyenoic fatty acid 22:6w3 in phospholipids of squid muscle is 42.6 to 45.7% of fatty acids (more than in the most active marine animals); (5) the large proportion of anaerobic metabolism of nitrogenous substances in energy metabolism enables the squid to inhabit zones of very low oxygen concentration.