瘦尾细额溞Oxyurella tenuicaudis(Sars,1862)的若干生物学特征

瘦尾细额溞是一种出现数量极其稀少的枝角类。关于它的生物学特征尚未见诸文献。本文测量了一次采自云南永胜一池塘的本种300个两性个体的体长和怀卵量,就其幼体与成体的数量、体长与怀卵量、雄性以及性比等问题探讨了种群的生物学状况。 详细观察比较了这个种的重要分类特征——雌体后腹部,并描述了变异范围。对卵鞍和雄体也作了描述。

SOME BIOLOGICAL DATA OF THE RARE CLADOCERA OXYURELLA TENUICAUDIS (SARS, 1862)

Three hemdvoel 300 individuals of Oxyurella tenuicaudis of both sexes and 3 ephjppia were selected from the plankton sample collected from a small pond in Yongsheng, Yunnan province on 26 Aug. 1982. Among them 265 are females occupied 88.3% of the total number of individuals. The body lengths are between 0.24 to 0.50 mm, but most of them are from 0.36 to 0.45mm. There are 110 females with eggs or embryos in their brood pouches, which occupy 41.5%, Lengths of their body are between 0.30 to 0.49mm. There are 64 females with only one egg occupying 58.2%, most of them are 0.36 to 0.39 mm long. 46 individuals each with two eggs are covering 41.8%, most of them are 0.41 to 0.45 mm long. There are 35 males among those 300 Oxyurella tenuicaudis, occupying 11.7%, their length are between 0.32 to 0.35 mm.Biological characters such as ratio of juvenile and adult, body length and brood size and sex ratio etc in the population of Oxyurella tenuicaudis are discussed, We infered that the population dynamics is of monocycle and begimto decline. The peak of population density has been passed whereas the males were continously increasing and the population would disappear in winter.The post-abdomen of 200 females were observed carefully and their variation were described.