Testicular Ecdysteroid Level in the Silkmoth, Bombyx mori, with Special Reference to Heat Treatment during the Wandering Stage

Abstract

Abstract To elucidate the induction mechanism of abnormal apyrene sperm by high temperature (32°C, 72 hr) treatment during the wandering stage of the silkmoth, Bombyx mori, ecdysteroid titres in the haemolymph and in the testes were determined. The fluctuation of ecdysteroids in the haemolymph was not disturbed by the high temperature treatment. The amount of ecdysteroids in the testes of control animals was low during the two-thirds of the last larval stage and an abrupt increase was observed on day 8. On the other hand, the elevation of ecdysteroid titre was suppressed in the testes of the treated animals during the period of treatment. After pupation, the fluctuation pattern of the ecdysteroid titre was almost the same both in control and treated animals. These results indicate that the deficiency of ecdysteroids in the testes could be the cause of the abnormal differentiation of the apyrene spermatozoa brought about by the high temperature treatment during the wandering stage of the silkmoth, Bombyx mori.