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The effect of methyl testosterone on secondary sex characters and reproductive behaviour of gonadectomized sticklebacks (Gasterosteus aculeatus L.) Wai, Evelyn

Abstract

Treatment of gonadectomized adult male and female sticklebacks as well as normal juvenile, with methyl testosterone, either by immersion in a hormone solution or by implanting hormone pellets, induces the kidney cells to develop into granular and mucous cells, accompanied by an increase in cell height. Increase in cell height, up to a limit, is a function of the length of hormone treatment. Prespawning aggressiveness and territoriality is induced in gonadectomized fish of both sexes by maintaining them under long photoperiod for four to five weeks. Short photoperiod has no effect. Administration of methyl testosterone to the already aggressive fish showed no definite effect on this behaviour. The combined effect of long photoperiod and methyl testosterone treatment induces the nest-building behaviour in gonadectomized males and females with a much higher percentage in the former than in the latter. The component elements of the nest-building movement in the treated gonadectomized male is similar qualitatively and quantitatively to that of the normal reproducing male. Treated gonadectomized females show deviations from the normal male in their nest-building movements. Sexual behaviour is the same in castrates treated with methyl testosterone as in the normal reproducing male, but completely absent in the similarly treated gonadectomized females.

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