两种新银鱼卵膜表面的亚显微结构研究

STUDY ON THE ULTRASTRUCTURE EGG SURFACE OF TWO SPECIES IN NEOSALANX (PISCES: SALANGIDAE)

滇池的新银鱼系80年代初期由江苏太湖引入,其分类地位一直被认定为Neosalanxtangkahkeii taihuensis Chen。张玉玲在全面整理中国新银鱼属的基础上,将该亚种提升为种,名太湖新银鱼N. taihuensis Chen,同时指出新银鱼属鱼卵膜表面具卵膜丝,并图示了光镜下观察到的各种新银鱼卵的卵膜丝形态及其分布情况,表明种间存在一定差异。

The fishes of Neosalanx were introduced into Dianchi Lake at the beginning of 1980's. It was believed that they belong only to one species, Neosalanx tangkahkeii taihuensis Chen. The present work shows that there are two types of eggs according to the results of scanning electron microscopical examination. One is with the short threads, the other is with long threads. Combining with the external characters of fishes, the authors consider that fishes in Dianchi Lake belong to two species. One is N. taihuensis Chen, whose egg surface is with short threads; the other is N. pseudoiaihuensis Zhang, whose egg surface is with long threads. The differences between their ultrastructures of egg surface may be expressed on two aspects. One is that their differences is a sign for identification. The other is that their differences may be a differentiation of reproductive isolation between two species. However, eggs with long threads can be attached on weeds, and eggs with short ones may sink to the bottom when they are spawned. The result is that their- eggs may occupy different levels in water. Earlier studies had shown that there were differences among some taxa in ultrastructures of egg surface, numbers and shapes of micropyle. It means that speciation, or differentiation among higher taxa, may be expressed on some ultrastructures of egg surface as record of evolution.