甲壳动物的环境型性决定和性比研究

Environmental sex determination and sex ratio in Crustacea

本文评述了甲壳动物的性决定和性比与环境关系问题的研究结果,论述了枝角类、端足类和其他甲壳动物的性决定的内、外因子,评价了Berg的“压抑”假说,并对今后该方面的研究重点,提出了意见和建议。

In the present paper, a brief account is given of the investigation of the environmental sex determination and sex ratio in Crustacea with special reference to Cladocera. The following are the main results of the investigation : (1) The sex of Cladocera such as Daphnia is determined about 4 h before the deposition of eggs in the brood pouch. The time of sensitive period of sex determination varies, however, with different species and also with environmental factors (chiefly temperature). (2) The sex of Amphipoda such as Gammarus is determined mainly by the male hormone secreted by the androgenic gland lying near the distal end of vas deferens. (.3) The sex determination of Crustacea is affected, without exception, by both external and internal faetros. Of the former, both low temperature and poor food are responsible for the male production, As to the latter, both metabolism and hormone play an important role in the male production. (4) A brief review is given of Berg's 'depression hypothesis' which shows that the crowding of parthnogenetic females of Cladocera (Daphnia and Moina) will lead to the production of sexual individuals by reducing metabolic rate and accurnmulation of metabolic wastes. (5) A considerable variation exists in the sex ratio of various groups of Crustacea, being caused by environmental factors, specially temperature ; but certain internal factors such as metabolism, age, longevity etc. can also affect sex ratio. Finally, the writer expresses his opinion that a greater attention should be paid to the evolutionary significance of sex determination and sex ratio and also to the aquarculture with the aim of producing more female crabs for human consumption.