Myxobolus Bütschli, 1882

Gao, Lei, Zhang, Jing, Yang, Chengzhong & Zhao, Yuanjun, 2020, Myxobolus jialingensis n. sp. (Myxozoa: Myxobolidae) infecting urinary bladder and hepatopancreas of yellowhead catfish Tachysurus fulvidraco from China, Zootaxa 4819 (1), pp. 179-186 : 181-183

Genus Myxobolus Bütschli, 1882

Taxonomic summary

Type host: Tachysurus fulvidraco (Richardson, 1846) ( Actinopterygii: Siluriformes : Bagridae ).

Type locality: Jialing River (29º58' N, 106º45' E), Shapingba District, Chongqing, China .

Sites of infection: urinary bladder, hepatopancreas.

Date of sampling: July 10, 2014.

Prevalence: Of the 70 fish examined, two were infected (2.9%).

Deposition of type materials: A syntype (mounted in glycerin-alcohol-formalin) has been deposited in the Collection Center of Chongqing Key Laboratory of Animal Biology , Chongqing Normal University, Chongqing, China (Coll. No. cq-2014071001). The DNA sample has been deposited in the same location, with the code number of cq-2014071002 .

Etymology: The species was named from the river (Jialing River), where the host was collected.

Morphological description. A single white oval cyst (3.1 × 2.8 mm) was discovered from hepatopancreas of a fish, and a white sphere cyst with a diameter of 3 mm detected in urinary bladder of another fish. Vegetative stages were not encountered. No obvious pathological traits for the host were observed. Therefore, the pathological damage to the fish remained unknown. The myxospores that infected the urinary bladder had a membranous sheath, and the spores from hepatopancreas had no ( Fig. 1 ). The morphology of the spore body (excluding the membranous sheath) from different infection sites were the same. The mature spore was pyriform with a slightly pointed anterior and blunt posterior, which was 15.8 ± 0.7 (15.4–17.0) µm in length and 8.0 ± 0.3 (7.8–8.9) µm in width (n=37). Two pyriform polar capsules were slightly unequal in size, with the larger one of 7.4 ± 0.3 (6.7–8.0) μm in length and 3.1 ± 0.2 (2.8–3.6) μm in width (n=37), and the smaller one of 7.3 ± 0.3 (6.6–8.1) μm in length and 3.3 ± 0.2 (2.9–3.6) μm in width (n=37). Polar filaments coiled with 7–8 turns ( Table 1).

Remarks. Of the approximately 900 species of Myxobolus described ( Eiras et al. 2005, 2014; Lom and Dyková 2006), M. jialingensis n. sp. has displayed similarity to Myxobolus voremkhai (Akhmerov, 1960) , Myxobolus pseudowulii Zhang et al., 2017 and Myxobolus xiantaoensis Tahir et al., 2019 , based on the fact that they all have pyriform spores with two unequal polar capsules ( Table 1). Also, the four species all parasitize on/in the same host, Tachysurus fulvidraco . However, they could be distinguished from each other by spore dimension, size of polar capsule, turns of filament coils and infection sites. The infection sites of the new species are urinary bladder and hepatopancreas rather than gills for M. voremkhai , skin for M. pseudowulii and fins for M. xiantaoensis . The spore and Abbreviations: SL, spore length; SW, spore width; PCL, polar capsule length; PCW, polar capsule width; NC, number of coils in polar filame. polar capsules of M. jialingensis n. sp. are slightly larger than that of M. voremkhai (15.4–17.0 μm × 7.8–8.9 μm vs. 13.1–15.5 μm × 7.1–8.6 in length and width of spores; 6.7–8.0 μm × 2.8–3.6 μm vs. 6.3–7.4 μm × 2.2–3.3 in length and width of the larger polar capsules; 6.6–8.1 μm × 2.9–3.6 μm vs. 5.8–7.1 μm × 2.2–3.3 in length and width of the smaller polar capsules) ( Table 1). And the number of polar filament coils for M. jialingensis n. sp. is much more than that of M. voremkhai (7–8 vs. 5–7). The new species has longer spores than M. pseudowulii (15.4–17.0 μm vs. 12.9–16.2 μm), and its proportion of the polar capsule in the whole spore is smaller than that of M. pseudowuli . The spore of M. jialingensis n. sp. is obviously longer and slightly narrower than that of M. xiantaoensis (15.4–17.0 μm vs. 11.3–13.9 μm in length; 7.8–8.9 μm vs. 8.4–11.1 μm in width).

The new species is somewhat similar to M. tunicatusb and M. macrocapsularis . They all infect urinary blad- der of T. fulvidraco . However, the new species could be distinguished from the later two by its two unequal polar capsules (vs. two equal size for M. tunicatusb and M. macrocapsularis ). And the morphometrics of the three species are apparently different ( Table 1).

Figures

FIGURE 1. Photomicrograph of fresh spores of Myxobolus jialingensis n. sp. from Tachysurus fulvidraco. (a) Spores (valvular view) from urinary bladder; the white arrows show the membranous sheath. (b) Spores (mostly extruded polar filament) from hepatopancreas; black arrow shows the spore in sutural view. (C) Line drawing of Myxobolus jialingensis n. sp. with and without membranous sheath, respectively. scale bar = 10 μm.