Respiration and the effects of pressure on the mesopelagic vertically migrating squid Histioteuthis heteropsis 1

The effects of hydrostatic pressure and dissolved oxygen concentration on oxygen consumption rates were examined in the mesopelagic, vertically migrating squid Histioteuthis heteropsis from southern California offshore waters. Elevated hydrostatic pressures (to 136 atm) had no significant effects on oxygen consumption rates at 5°C. Low oxygen concentrations (<0.5 ml O2 · liter−1) depressed rates of oxygen consumption. These findings suggest that metabolism is pressure insensitive during vertical migrations and that at least partial anaerobiosis may be necessary to supply the total energy needs of this species at daytime depths in the oxygen minimum layer off southern California.