鲤肠道寄生岳阳碘泡虫新种的形态特征及系统发育分析

MORPHOLOGICAL AND MOLECULAR CHARACTERISTIC OF MYXOBOLUS YUEYANGENSIS SP. NOV.(MYXOZOA: MYXOBOLIDAE) FROM THE INTESTINE OF COMMON CARP(CYPRINUS CARPIO) IN CHINA

在洞庭湖岳阳地区开展鱼类寄生虫调查中,发现一种寄生于鲤Cyprinus carpio L.肠道的黏孢子虫。该黏孢子虫的孢囊呈白色,椭圆形,大小为(1.0±0.2)mm(0.8—1.2 mm)。成熟孢子具有壳瓣,壳面观近似圆形,后端有4—6个"V"形褶皱;缝面观呈纺锤形,缝脊直而粗;孢质均匀,含有一个嗜碘泡;孢子长(9.8±0.6)μm(9.6—10.0μm),孢子宽(8.2±0.3)μm(8.0—8.5μm),孢子厚(7.3±0.1)μm(7.0—7.5μm);2个极囊梨形,位于孢子顶端,大小相等,呈"八"字形;极囊长(4.4±0.4)μm(3.8—5.1μm),宽(2.7±0.2)μm(2.2—3.2μm),极丝4—5圈。该黏孢子虫与肠膜碘泡虫、丑陋圆形碘泡形态特征非常相似,但其极囊/孢子小于1/2;与文献已报道的鲤肠道寄生北京碘泡虫和鲤肠碘泡虫相比较,其在孢子形态、孢子和极囊大小方面分别存在明显差异。基于该黏孢子虫18S r DNA基因序列(Gen Bank登录号KY203795)比对分析,该黏孢子虫与山东碘泡虫相似率最高,仅为96%。系统发育分析发现,该黏孢子虫与山东碘泡虫、倪李碘泡虫、住心碘泡虫、Myxobolus encephalicus、Sphaerospora molnari、多涅茨尾孢虫和Henneguya zikaweiensis聚为独立分支,和其他已报道的黏孢子虫亲缘关系较远。综合形态学和18S r DNA基因序列数据,文章报道的鲤肠道寄生黏孢子虫为碘泡虫属一新物种,将其命名为岳阳碘泡虫。

Myxobolus yueyangensis sp. nov. parasitic in the intestine muscularis of common carp Cyprinus carpio with the form of round or ellipsoidal plasmodia, was found during a survey on fish myxozan diversity in Yueyang（29°37′N, 113°09′E）. Mature spores were suborbicular in frontal view, and fusiform in back view, measuring 9.8±0.6（9.6—10） μm long, 8.2±0.3（8.0—8.5） μm wide, and 7.3±0.1（7.0—7.5） μm thick. The surface of spores was smooth,and a round iodinophilous vacuole was found in its uniform protoplasm. Two Polar capsules were pyriform with an apophysis at its top and end closed to apex of spore, measuring 4.4±0.4（3.8—5.1） μm in length, 2.7±0.2（2.2—3.2） μm in width. Polar filaments coiled 4 to 5 turns. M. yueyangensis is morphologically distinct from all other Myxobolus species. The BLAST search indicated that the newly obtained small subunit ribosomal RNA（ssr RNA） gene sequence did not match any available sequences in Gen Bank, and showed the high similarity with Myxobolus yueyangensis of 96%.In the phylogenetical tree, M. yueyangensis was closely clustered with Myxobolus yueyangensis. Based on the comparison and analysis of spore morphology, host specificity, tissue or organ parasitized specificity, and 18 S r DNA sequence, the myxosporean from the intestine of C. carpio described in the study should be a new species of genus Myxobolus.