日本鲺(Argulus japonicus)寄生大口黑鲈的首次报道及分子系统发育研究

First report of Argulus japonicus on largemouth bass and phylogenetic analysis of Argulus

通过形态学和分子生物学的方法对1种寄生于大口黑鲈体表的鲺(Argulus sp.)进行鉴定,并根据SSU rDNA序列探究鲺属内物种的系统发育关系。结果显示:鲺体呈淡黄色;雌性体长1.93±0.46(1.42~2.54)mm,雄性体长2.18±0.49(1.57~2.87)mm;背甲马蹄形,侧叶末端伸达第三游泳足后缘;吸盘由多条(雌性:44~52;雄性:46~47)几丁质条组成,每条几丁质条含不等数量(雌性:5~6;雄性:7~8)的几丁质片。形态学与形态测量学结果与日本鲺(Argulus japonicus Thiele,1900)最为相似。比对该物种SSU rDNA序列发现与日本鲺JN558647的序列相似性高达99.77%(1274/1277),进一步支持鉴定为日本鲺。ML系统进化树显示:鲺属内物种主要分为3个进化支;其中,日本鲺株系多位于Clade I中且与A.foliaceus和A.rhipidiophorus呈并系类群;本次采集的日本鲺(MW866569)聚于Clade I的基部,与日本鲺KF747859和KF747860株系亲缘关系最近。

During a survey of parasitic disease,a species of Argulus was isolated from the cultured largemouth bass(Micropterus salmoides)at a fish farm in Wuhan,China.Morphological and morphometric analysis were conducted to identify the species and phylogenetic analysis of Argulus were carried out based on SSU rDNA.The results showed that the parasite was in faint yellow.The total length was 1.93±0.46(1.42-2.54)mm for female and 2.18±0.49(1.57-2.87)mm for male.The carapace was horseshoe shaped,with branched pigments scattered throughout the lobes.The sucker consisted of chitinous strips(female:44-52,male:46-47),each of which contains varying amounts of chitinous tablets(female:5-6,male:7-8).Unreleased eggs were founded in the abdomen of female and symmetrical testis were observed in the male’s abdomen.Morphological and morphometric data was in consistent with Argulus japonicus Thiele 1900.Phylogenetic analysis based on ML phylogenetic tree of SSU rDNA showed that Argulus species was divided into three clades.A.japonicus isolates were mainly clustered into Clade I and paraphyletic grouped with Argulus foliaceus and Argulus rhipidiophorus.In conclusion,we identified the Argulus sp.isolated from the largemouth bass as A.japonicus based on the above morphological and morphometric data.Further phylogenetic analysis was also conducted to discuss the phylogenetic relationship within Argulus.To our knowledge,this is the first report of the parasitism of A.japonicus on largemouth bass.