THE INFLUENCE OF SEASONAL ENVIRONMENTAL CHANGES UPON THE METABOLISM, LETHAL TEMPERATURE AND RATE OF HEART BEAT OF GAMMARUS LIMNAEUS (SMITH) TAKEN FROM AN ALASKAN LAKE

Abstract

1. A year's cycle of the oxygen consumption of the amphipod, Gammarus limnaeus (Smith), has been recorded. The metabolism has been related to the environmental factors encountered in a shallow Alaskan lake, which is ice-covered during seven winter months. 2. A seasonal change in the metabolic rates of the animals accompanied changes in the available oxygen. These resulted in decreased oxygen consumption during the winter when the oxygen supply in the lake was low. 3. The lethal temperature of the amphipods changed from 26° C. in winter to 30°-32 C. in summer. 4. The rate of the heartbeat of the animals varied slightly with the season, with a higher average rate at temperatures below 20° C. in winter than in summer.