AN EFFECT OF DILUTIONS OF SEAWATER ON THE LETHAL TEMPERATURE OF THE GUPPY

Abstract
Two phases of resistance times with decreasing upper lethal temperatures are shown for guppies acclimated to 25 °C, with a more marked increase in resistance between 37° and 36 °C than for the same increment at higher or lower temperatures in fresh water. Increased salinity has little effect at high (39 °C) and low (34°) lethal temperatures. At 38° and 37 °C thermal resistance is increased by ⅛ seawater and still more so by ¼ seawater, as might be expected since the latter is approximately isosmotic. However, at 36° the least resistance is obtained in ¼ seawater.

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