Weight fluctuation in frogs

Abstract

It is known that frogs lose weight when removed from water or very moist places and are placed in dry surroundings; and that gain in weight occurs under reversed conditions. 1 To test the magnitude of such change under local laboratory conditions, beginning in 1909, several series of experiments have been performed. Leopard frogs (Rana Pipiens) were used.

The first series were performed during June and July and the laboratory was not heated. During the day the windows were opened and the temperature varied from about 23.6° to 30.2° C. Night temperatures were not taken, but the minimum observed by the local weather bureau for the period was 16.7° C. Showers occurred during the experiment, so the air was not abnormally dry.

Placed in water and weighed hourly, a maximum hourly fluctuation of 10 per cent., a minimum o, and an average for 10 hours of 3.8 per cent, was observed. A total gain in weight amounting to 20 per cent. occurred. Placed in wire cages in the air of the laboratory a very rapid loss of weight occurred, amounting to as much as 40 to 45 per cent. of the original weight in twenty-four hours. If the loss was not greater than this, recovery might take place if the animal were placed in water. The gain in weight was very rapid, the total weight within four hours amounting to as much as 121 per cent, of the original weight, or 200 per cent, of the weight after drying. During the next sixty hours, the weight fluctuated moderately, rising during the afternoon of the second day to 136 per cent. of the original weight before drying.

The time of death by drying is not very exactly shown by the experiments, owing in part to the sluggish reactions supervening.