The biology and metabolism ofOrchomene plebs (Hurley 1965) (Amphipoda: Gammaridea) from McMurdo sound, Ross Sea, Antarctic

Summary

O. plebs (Hurley 1965) is a dominant bottom species of amphipoda, occuring in the investigated area at 10 to 760 m. Population structure and sex proportions depend upon the depth and the season of the year of sampling. Development of eggs occurs in winter; the young hatch in spring; the number of eggs produced is proportional to the volume of females. A relationship has been established between length and wet/dry body weight ofO. plebs. The species is necrophagus, long enduring without food. At -1.8°C retention of food in the gut may last from several hours to several days. Heart beat frequency oscillates between 40–80 beats/min at -1.8°C and depends on temperature. A temperature near 8°C is lethal. Oxygen consumption ofO. plebs depends on their developmental stage and sex and on trophic conditions. The level of metabolism of starved animals can be half that of fed animals. The greatest differences in oxygen consumption occur at-1.8°C, the ambient temperature. Oxygen consumption as a reaction to higher temperatures is different for starved and fed animals.O. plebs are hypostenothermic organisms; that is, they can adapt to the lowest temperature occuring in the marine environment.