Energy balance and cold adaptation in the octopus Pareledone charcoti
A complete energy balance equation is calculated for the Antarctic octopus Pareledone charcoti at 0°C. Energy used in respiration, growth, and excretion of nitrogenous and faecal waste, was recorded along with the total consumption of energy through food, for three specimens of P. charcoti (live weights: 73, 51 and 29 g). Growth rates were very slow for cephalopods, with a mean daily increase in body weight of only 0.11%. Assimilation efficiencies were high, between 95.4 and 97.0%, which is consistent with previous work on octopods. The respiration rate in P. charcoti was low, with a mean of 2.45 mg O2 h−1 for a standard animal of 150 g wet mass at 0°C. In the North Sea octopusEledone cirrhosa, respiration rates of 9.79 mg O2 h−1 at 11.5°C and 4.47 mg O2 h−1 at 4.5°C for a standard animal of 150 g wet mass were recorded. Respiration rates between P. charcoti and E. cirrhosa were compared using a combined Q10 value between P. charcoti at 0°C and E. cirrhosa at 4.5°C. This suggests that P. charcoti are respiring at a level predicted by E. cirrhosa rates at 4.5 and 11.5°C extrapolated to 0°C along the curve Q10=3, with no evidence of metabolic compensation for low temperature.