石斑角形虫(黏体门, 角形虫科)的分子证据及其在不同宿主中的遗传变异

FIRST MOLECULAR EVIDENCE OF CERATOMYXA EPINEPHELA(MYXOZOA:CERATOMYXIDAE)AND ITS GENETIC VARIATION FROM DIFFERENT HOST SPECIES

研究从中国东海的青石斑鱼Epinephelus awoara Temminck&Schlegel 1842和褐带石斑鱼E.bruneus Bloch 1793的胆囊中检获了石斑角形虫Ceratomyxa epinephela Wu,Wu et hua,1993,首次提供了其SSU rDNA和ITS1 rDNA序列,并基于形态学和分子数据进行了重新描述。石斑角形虫成熟孢子的孢子长(4.8±0.5)μm(3.6—5.6μm),孢子厚(31.8±4.8)μm(23.3—37.5μm);孢子壳瓣光滑且等大,由垂直的缝线连接;极囊长(2.9±0.2)μm(2.4—3.7μm),极囊宽(2.6±0.2)μm(2.2—3.1μm);孢子夹角处稍微凹陷,延伸至两端逐渐变平坦,夹角为(175.9±3.7)°(165.5°—179.7°)。基于SSU rDNA序列构建的系统发育树显示石斑角形虫与诺兰角形虫C.nolani Gunter&Adlard 2009,卡特莫尔角形虫C.cutmorei Gunter&Adlard 2009和横山角形虫C.yokoyamai Gunter&Adlard 2009有很近的亲缘关系,且其宿主均为石斑鱼属物种。结果表明,类群关系较近的宿主其寄生的同属黏孢子虫可能具有更近的系统发育关系。基于SSU rDNA和ITS1 rDNA的遗传分析显示,石斑角形虫的4个分离株已发生了明显的遗传分化(形成了4个基因型),形成了不同的种群,但在不同宿主种类间并未形成特有的分化。

Ceratomyxa epinephela Wu,Wu et Hua,1993 is originally found to infect the gallbladder of Epinephelus akaara Temminck&Schlegel,1842 from South China Sea,and no molecular data have been provided up to date.In the present study,we detected this species infecting the gallbladder of E.awoara Temminck&Schlegel,1842 and E.bruneus Bloch,1793 from East China Sea.For the first time,we offered the SSU rDNA and ITS1 rDNA information for this species and redescribed such species based on the combination of morphological and molecular data.Mature spores of C.epinephela were(4.8±0.5)μm(3.6—5.6μm)in length and(31.8±4.8)μm(23.3—37.5μm)in thickness.Myxospores valves were smooth and almost equal,which were joined by a prominent suture.Polar capsules measured(2.9±0.2)μm(2.4—3.7μm)in length and(2.6±0.2)μm(2.2—3.1μm)in width.Posterior angle was slightly concave to flat,measured(175.9±3.7)°(165.5°—179.7°).Phylogenetic analysis based on SSU rDNA revealed that C.epinephela had the close relationship with C.nolani Gunter&Adlard,2009,C.cutmorei Gunter&Adlard,2009,and C.yokoyamai Gunter&Adlard,2009,all of whose host were epinephelids.It also implied that the close host affinity might have close phylogenetic relationships of their myxosporean parasites.The sequences analysis based on SSU rDNA and ITS1 rDNA revealed that the four isolates of C.epinephela had already formed different populations,while the species did not form a specialized genetic characteristic among its different host species.