Zhang Bo, Zhai Yanhua, Liu Yang, Gu Zemao
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, People's Republic of China.
Key Lab of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, People's Republic of China.
Folia Parasitol (Praha). 2017 Sep 27;64:2017.030. doi: 10.14411/fp.2017.030.
Two species of Myxobolus Bütschli, 1882 were found in yellow catfish Tachysurus fulvidraco (Richardson). A species of Myxobolus infecting the gills was morphologically identified as Myxobolus voremkhai (Akhmerov, 1960) and it was characterised here with additional morphological and molecular data. The other species of Myxobolus infecting the host's skin did not conform to any known myxosporean species. It is characterised by the presence of round, black or milky white plasmodia with black spots. Myxospores are pyriform in frontal view and lemon-shaped in lateral view, measuring 12.9-16.2 μm (14.6 ± 0.7 μm) in length, 8.1-10.8 μm (9.4 ± 0.5 μm) in width, and 6.1-8.1 μm (7.0 ± 0.4 μm) in thickness. Two ampullaceous polar capsules are slightly unequal in size, larger polar capsule 7.2-9.5 μm (7.9 ± 0.4 μm) long by 3.0-3.9 μm (3.5 ± 0.2 μm) wide, smaller capsule 6.9-8.0 μm (7.4 ± 0.3 μm) long by 2.9-3.9 μm (3.4 ± 0.2 μm) wide. Polar filaments are coiled with seven to nine turns. Histologically, the plasmodia develop in the stratum spongiosum of skin dermis, resulting in epithelial cell shedding and immunological cell infiltration. Given the morphological and molecular differences between this species and other species of Myxobolus, we proposed the name of Myxobolus pseudowulii sp. n. for this parasite from the skin of yellow catfish. Interestingly, some spores of the new species possess Henneguya-like caudal appendages. Phylogenetically, M. pseudowulii sp. n. and M. voremkhai infecting yellow catfish group together in one clade with other parasites of Siluriformes, indicating that parasites clustering according to the fish host order may be an important factor affecting the evolution of species within the Myxobolus clade.
在黄颡鱼（Tachysurus fulvidraco (Richardson)）中发现了两种1882年布氏粘体虫属（Myxobolus Bütschli）的粘孢子虫。一种感染鳃的粘体虫在形态上被鉴定为沃氏粘体虫（Myxobolus voremkhai (Akhmerov, 1960)），在此通过额外的形态学和分子数据对其进行了特征描述。另一种感染宿主皮肤的粘体虫不符合任何已知的粘孢子虫物种。其特征是存在带有黑点的圆形、黑色或乳白色的孢囊。粘孢子虫正面观呈梨形，侧面观呈柠檬形，长12.9 - 16.2μm（14.6 ± 0.7μm），宽8.1 - 10.8μm（9.4 ± 0.5μm），厚6.1 - 8.1μm（7.0 ± 0.4μm）。两个瓶状极囊大小略有不等，较大的极囊长7.2 - 9.5μm（7.9 ± 0.4μm），宽3.0 - 3.9μm（3.5 ± 0.2μm），较小的极囊长6.9 - 8.0μm（7.4 ± 0.3μm），宽2.9 - 3.9μm（3.4 ± 0.2μm）。极丝盘绕七到九圈。组织学上，孢囊在皮肤真皮的海绵层中发育，导致上皮细胞脱落和免疫细胞浸润。鉴于该物种与其他粘体虫物种在形态和分子上的差异，我们为这种来自黄颡鱼皮肤的寄生虫提出了伪伍氏粘体虫（Myxobolus pseudowulii sp. n.）这一名称。有趣的是，新物种的一些孢子具有类似赫氏虫属（Henneguya）的尾突。在系统发育上，感染黄颡鱼的伪伍氏粘体虫和沃氏粘体虫与鲇形目其他寄生虫一起聚集在一个进化枝中，这表明根据鱼类宿主目进行聚类的寄生虫可能是影响粘体虫进化枝内物种进化的一个重要因素。
