马颈鱼虱属(寄生桡足类)一新种及其与近缘种的比较

A NEW PARASITIC COPEPOD OF THE GENUS TRACHELIASTES AND IN COMPARISON WITH ITS AFFINITIES

马颈鱼虱属(Tracheliastes Nordmann,1832)是隶属于颚虱科(Lernaeopodidae)的寄生桡足类,迄今为止世界上已报道过的有6种,其中我国已有记载的3种,即普通马颈鱼虱T.polycolpus Nordmann,长颈马颈鱼虱T.longicollis Markewitsch和西藏马颈鱼虱T.tibetanus Kuang。最近在云南宁蒗县泸沽湖的裂腹鱼Schizothorax sp.上发现了二种马颈鱼虱,一种寄生在鳍上的为普通马颈鱼虱,另一种寄生在鳃盖内侧上角的为未记载过的新种,现报道如下.

Tracheliastes brevicorpus, sp. nov. Holotype♀ , No. 78040454, from Lugu Lake , Ninglang Xian, Yunnan, 1978. Paratypes 9 ♀♀, from the same locality . Host. Schizothorax sp. Measurements. Cephalothorax 2.02- 2.67 mm;trunk 1.67-2.02mm, its width 1.03-1.60mm. first maxillipeds 0.94-1.64mm. Diagnosis. This new species differs from other congeneric species in having a shorter and broader trunk, and in having a shorter 1st maxilliped. Remarks. In the genus Tracheliastes, only T. polycolpus has a wide range of geographical distribution in Eurasia, others are all confined either in Europe or Asia. So far as known T. polycolpus has been recorded to parasitize on fishes belonging to 12 genera of the family Cyprinidae. These fishes are very different from each other in their living habits and ecological demands. In this sense, T. polycolpus is a species of wide adaptation, while T. sachalinensis, T. tibetanits, T. chondrostomi and T. brcvicorpys only found on fishes of one genus are considered to be of narrow adaptation . There are five species of the genus Tracheliasles parasitic on fins and scales of fis-hes , two species on gills and inside the opcrculum. Changing of parasitic location from body surface to branchial chamber is an important step in the course of evolution of the parasite. It shows the deepening of parasitic degree. ]n this way the parasites arc more or less protected from being harmed or rubbed off and it is available to parasitism. This new species and T. polycolpus may be found on one host fish at the same time. But the former is parasitic inside the operculum and the latter is parasitic on fins without any confusion. It suggests that the ecological demand of the two species is very distinct. Basing on morphological comparison, the new species resembles T. tibetanus in lengths of cephalothorax and trunk . Both are parasitic inside the branchial chamber of the hosts belonging to a common genus Schizothorax . On geographical distribution, North Yunnan is adjacent to Xizang. In considering of these aspects in combination it seems to be probable that this new species is closely related to T . tibetanus .