紫黑翼蚌钩介幼虫寄主鱼的人工筛选及寄生包囊形成观察

ARTIFICIAL SELECTION OF SUITABLE HOST FISH AND PARASITIC CYST FORMATION OF GLOCHIDIA IN PINK HEELSPLITTER,POTAMILUS ALATUS

选取16种鱼类,对紫黑翼蚌(Potamilus alatus)钩介幼虫寄主鱼进行人工筛选试验,结果表明:仅在淡水石首鱼(Aplodinotus grunniens)上获得变态发育的稚蚌,寄生变态率为(49.6±9.4)%,但是过量寄生将导致淡水石首鱼的死亡。除眼斑拟石首鱼(Soiaenops ocellatus)外,寄生在其他14种淡水鱼类均不可能实现钩介幼虫的变态。进一步扫描电镜观察显示:钩介幼虫可在与淡水石首鱼同科的眼斑拟石首鱼鳃丝寄生并形成完整的包囊,且在大规格鱼体形成包囊的速度明显快于幼鱼。但在寄生和淡水低渗双重胁迫下,眼斑拟石首鱼出现极高的死亡率,提示应进一步开展淡化驯养以提高眼斑拟石首鱼寄生后的成活率。其中黄颡鱼(Pelteobagrus fulvidraco)、小口黑鲈(Micropterus dolomieu)、蓝鲶(Ictalurus furcatus)寄生后1—2d内脱落的幼虫几乎全部死亡,推测3种鱼体中可能存在紫黑翼蚌幼虫的致死因子。综合研究表明:紫黑翼蚌是目前发现对寄主鱼选择性最为专一的蚌类,而眼斑拟石首鱼具有作为替代寄主鱼的潜能。

16different fish species were tested to select suitable host fish for pink heelsplitter,Potamilus alatus.Theresults showed that transformed juveniles were only obtained from freshwater drum Aplodinotus grunniens,the onlysuitable host fish for pink heelsplitter,and the average transformed rate was(49.6±9.4)%,and that over parasitic causedmortality of infested fish.It was proven that other14freshwater fish species except red drum Sciaenops ocellatus haveno potential as host of pink heelsplitter.SEM showed that glochidia could infest on the gill of red drum that belong tothe same family as freshwater drum,and form parasitic cyst with faster on large red drum than juveniles.However,theinfested red drum showed a rather high mortality rate under the double stress of infestation and low osmotic in freshwater,suggesting that desalination and nutrient intensive cultivation should improve the survival rate of infested red drum.The glochidia detached from yellow catfish,smallmouth bass and blue catfish in1-2d after infestation almost all died,suggesting that certain larval lethal factors may exist in these fishes.Comprehensive analysis indicated that pinkheelsplitter was the most specific Unionidae species for host fish,and the red drum might be the potential host for pink heelsplitter.