THE RESISTANCE AND ACCLIMATIZATION OF MARINE FISHES TO TEMPERATURE CHANGES. II. EXPERIMENTS WITH FUNDULUS AND ATHERINOPS

¹ Scripps Institution of Oceanography, University of California, La Jolla

The resistance of the hardy marine fish Fundulus parvipinnis and of the delicate Atherinops affinis to low and high temperatures is examined in relation to temperatures of previous acclimatization and to temperature conditions in the natural habitats of the fishes.

The relationships between the time (duration) of exposure to test temperatures and the average (median) limits of temperature tolerance indicate the value of prolonged tests in the study of resistance to cold and heat.

Marked susceptibility of marine fishes to chilling (i.e., injury at non-freezing low temperatures) and the influence of acclimatization upon temperature tolerance are confirmed.

The death of Fundulus at slowly lethal low temperatures, but not at rapidly lethal temperatures, is preceded in the normal medium (sea water) by evident dehydration of the tissues and is delayed by dilution of the medium. Osmoregulative failure is indicated as one of the causes of slow death at low temperatures in sea water, but not of rapid death at more extreme low temperatures, which may be caused partly by respiratory disturbances.