Myxobolus linzhiensis n. sp. (Myxozoa: Myxobolidae) from the gill filament of Schizothorax oconnori Lloyd (Cyprinidae: Schizothoracinae) in Tibet, China: morphological and molecular characterization

Abstract

In this report, a new myxosporean species, Myxobolus linzhiensis n. sp. (Cnidaria: Myxozoa: Bivalvulida), was described from the endemic cyprinid Schizothorax oconnori inhabiting the Yarlung Tsangpo River in the Tibetan plateau, China. The whitish ellipsoidal plasmodia of M. linzhiensis n. sp. grew under the epithelium of gill filaments, 1.7-mm long and 0.4-mm wide, and were found in the 3 of 8 examined S. oconnori (37.5%). Mature spores appeared suborbicular in frontal view, fusiform shaped in lateral view with tapering anterior, measuring 11.4 ± 0.7 (10.1-13.0) μm in length, 10.6 ± 0.4 (10.0-11.3) μm in width, and 6.6 ± 0.3 (6.2-7.0) μm in thickness. Two equal polar capsules were pyriform with an apophysis at its top end, measuring 5.7 ± 0.5 (4.8-6.7) μm in length, 3.8 ± 0.2 (3.2-4.2) μm in width, and polar filaments coiled 4 turns. Spore valves were symmetrical, and sutural ridge was straight and thin, running near the middle of the valves. Although Myxobolus linzhiensis n. sp. showed similar morphological characteristics with Myxobolus chushi Dar Kaur & Chishti 2017 from Schizothorax niger, Myxobolus kienweiensis Ma, 1976 from Schizothorax davidi, the new myxosporean was distinguished with them in spore shape, polar filament, and host-tissue tropism. Homology search by BLAST in GenBank indicated that the obtained 18S rDNA sequence of M. linzhiensis n. sp. (KY965935) did not match any available myxozoan sequence, most similar to Henneguya zikaweiensis, and showing less than 93% sequence similarity. Phylogenetical analyses demonstrated that M. linzhiensis n. sp. was firmly clustered in the clade consisting of myxosporeans Thelohanellus, Myxobolus, Henneguya from Asian cyprinids. This study is the first report on myxosporean parasitizing in endemic fish in the Tibetan Plateau, China.

Morphological, histopathological and molecular characterization of Myxobolus szekelyianus n. sp. (Cnidaria: Myxosporea: Myxobolidae) causing acute gill disease in Schizothorax esocinus (Heckel, 1838) from River Jhelum of Kashmir Himalayan region, India

“…By its large plasmodia and the shape and size of the spores, M. szekelyensis resembles the best to the species M. linzhiensis described by Li et al (2017) from Schizothorax oconnori, but in plasmodia of the latter species, there is only a small iodinophilous vacuolum, and polar fil- and Gupta and Kaur (2017a), in which reported that largesized plasmodia can result in more than 50% damage to the gills, eventually affecting the respiratory system. Such damages induce less functioning of gills and accessory respiratory system by reducing the surface of respiratory system as described by Eissa (2002) and Sabri et al (2010).…”