Effects of prolonged starvation on O2 consumption,NH 4 + excretion,and chemical composition of the bathypelagic mysid Gnathophausia ingens

The large bathypelagic mysid Gnathophausia ingens was collected in January 1980 at 400 to 700 m depth from the San Clemente Basin off southern California. Instars 7-8 and Instars 10-12 were starved in the laboratory for up to 19 wk. Oxygen consumption and ammonia excretion rates, and water, protein, lipid, and ash contents were determined periodically during starvation. Protein and lipid were metabolized in approximately equal amounts by starved individuals after the initial weeks of food deprivation. Unidentified components (probably non-protein nitrogenous compounds) apparently were oxidized within the first 7 wk of starvation. Oxygen consumption and ammonia excretion by Instars 7-8 decreased steadily during 19 wk of starvation. In contrast, stable or increasing respiration and excretion rates were observed for fed mysids. The mean respiration rate of Instars 10-12 did not change significantly during 13 wk of starvation, although ammonia excretion rates decreased. Low metabolic rates and large lipid reserves probably help G. ingens to withstand long periods of starvation in the mesopelagic environment. Calculations based on the laboratory data demonstrate that small, infrequent meals could account for the rates of metabolism and growth observed for G. ingens in the field.