Seasonal and Experimental Variations of the Oxygen Consumption of the Limpet Ancylus Fluviatilis (O. F. Müller)

Abstract

ABSTRACT A seasonal variation of the oxygen consumption of the limpet Ancylus fluviatilis occurs in populations both from a lake and from a stream. In spring and early summer the oxygen consumption is higher than at other seasons of the year. The increased oxygen consumption in spring and early summer is most probably caused by reproductive activity. A decrease of the growth rate in spring and early summer, computed on the basis of Hunter’s observations (1953), must also be regarded as caused by reproductive activity. Partial starvation appears to have considerable influence on the rate of respiration. A comparatively high, but not constant oxygen consumption occurs during the first hours after collection, then, in consequence of partial starvation, a distinct decrease of the oxygen consumption follows, and finally, 50 hr. after collection, a slighter decrease. During partial starvation the decrease of the oxygen consumption is greater at high than at low temperatures. When the partial starvation is severe the decrease of the oxygen consumption commences earlier than under somewhat better food conditions. The oxygen consumption of limpets which had the opportunity of taking food from alga-covered stones in an aquarium decreased after 3 days, but the decrease seems to be less than in the case of partial starvation. The oxygen consumption of the limpets which starved completely decreased rapidly during the period 0–20 hr. after the start of the series of experiments. There was no time at the beginning of the starvation period in which the animals had a nearly constant oxygen consumption. After the period 0–20 hr. the decrease continued, but apparently in diminishing degree; 96 hr. after the beginning of the starvation the oxygen consumption had declined to about three-fifths of the initial value. The oxygen consumption of animals first starved for 96 hr. and then given food when placed on alga-covered stones in the river for 3 days again increased considerably, but not to the initial value. The oxygen consumption in relation to the temperature was found in the main to follow the so-called Krogh’s curve from 11 to 18° C. after a gradual temperature increase (c. 1° C. per hour), but not after an abrupt increase. The first result confirms earlier observations (Berg, 1952). It does not always seem certain, however, that the increase of oxygen consumption in experiment will follow Krogh’s curve completely, even if the temperature increases slowly. Experiments with limpets which may be regarded as adapted to different temperatures in nature show that their oxygen consumption in relation to temperature in October to February, i.e. outside the reproduction period, varies according to Krogh’s curve. In shaken bottles the oxygen consumption appears to be greater than in still bottles. The slope of the regression line, tan a, showing the oxygen consumption in relation to weight in a logarithmic co-ordinate system, tends towards 0·70−0·75 when the correlation coefficient, which expresses the dependence of the respiration on weight, increases towards 1 (Fig. 15, p. 67). On the basis of twenty-two experiments the slope of the regression lines has been calculated to be 0·716 ± 0·034.