COLD DEATH IN THE GUPPY

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Abstract
Exposure to water of 10[degree] C or colder caused "primary chill coma" i. e. convulsions, loss of vital signs, and death unless rewarmed. Exposure to lethal cold temperatures above 10[degree] C caused "secondary chill coma" i. e. vital signs disappear but return and the fish then gradually die unless rewarmed. The lethality of "secondary chill coma" was unaltered by increase of the O2 content of the chilling water from 10 to 45 mg O2/L. or chilling in isosmotic sodium chloride solution. In "primary chill coma", upon rewarming, respiration did not return in any fish subjected to 3 or more times the LD50 exposure, but the circulation returned in all fish subjected to 12 or less times the LD50 exposure. Lethality of an exposure causing "primary chill coma" was: (1) increased by decrease of the O2 content of the water from 10 to < 0.3 mg/L before or during an exposure; (2) decreased by prior anesthesia with 1% urethan or by increase of the O2 content of the water from 10 to 50 mg/L during or after an exposure; (3) unaltered by increased O2 content before an exposure, decreased O2 (of a duration which was not lethal of itself) after an exposure, or by equilibration of the chilling water with 5% CO2. The data indicate that the lethal effect of "primary chill coma" is related to the profoundness of respiratory depression and to the degree of depletion of the fish''s oxygen reserve. Death due to "primary chill coma" in the guppy seems to be due to anoxic damage to a cold-depressed respiratory center.