Metabolism of benthic octopods (Cephalopoda) as a function of habitat depth and oxygen concentration

The oxygen consumption rates and activities of key metabolic enzymes were m easured and analyzed as a function of habitat depth for several species of benthic octopod (Cephalopoda: Octopoda) including a recently described hydr othermal vent endemic species. Oxygen consumption rates and citrate synthas e activity, an indicator of aerobic metabolic potential, did not vary signi ficantly with increasing habitat depth. Anaerobic metabolic potential, as e videnced by octopine dehydrogenase activity, declined significantly with in creasing habitat depth. It is suggested that burst swimming abilities, and hence glycolytic potential, are not strongly selected for in the deep-sea, where Visual predator-prey interactions are reduced because of light-limita tion. Oxygen consumption rates for Octopus californicus and O. bimaculoides were analyzed as a function of oxygen partial pressure as well. O. califor nicus, which lives in the hypoxic Santa Barbara basin at 500 m depth, was a ble to regulate its oxygen consumption to the limit of detectable oxygen pa rtial pressures. O. bimaculoides, an intertidal species, had a minimum crit ical oxygen partial pressure of 16 mmHg. It is also shown that oxygen consu mption rates and oxygen consumption regulation are strongly affected by ind ividual experiment duration (either handling stress or food deprivation). O . californicus appears to be much more strongly affected by experiment dura tion than is O. bimaculoides. (C) 2000 Elsevier Science Ltd. All rights res erved.