Myxobolus parakoi, Liu & Zhang & Yang & Zhao, 2019

Liu, Xiaohua, Zhang, Diaodiao, Yang, Chengzhong & Zhao, Yuanjun, 2019, Morphological and molecular identification of Myxobolus parakoi sp. nov. (Myxozoa: Myxobolidae), from Cyprinus carpio in Chongqing China, Zootaxa 4657 (1), pp. 117-126 : 119

Myxobolus parakoi sp. nov.

( Fig. 1 )

Phylum Cnidaria Hatschek, 1888

Unranked Sub-phylum Myxozoa Grassé (1970)

Class Myxosporea Bütschli, 1881

Order Bivalvulida Shulman, 1959

Family Myxobolidae Thélohan, 1892

Genus Myxobolus Bütschli, 1882

Taxonomic summary

Type host: Common carp Cyprinus carpio (Linnaeus, 1758) .

Site of infection: Gill lamellae.

Prevalence: Of the 26 fish examined, one was infected (3.8%).

Type locality: Jialing River, Shapingba District, Chongqing, China (29º30’ N, 106º27’ E).

Deposition of type materials: Syntype specimens (No. CQSpb-Cc-201710) have been deposited at the Collection Center of type-specimens, Chongqing KLAB, Chongqing Normal University, China.

Etymology: The specific name “ parakoi ” is referred to the morphological similarity of this organism to Myxobolus koi Kudo, 1919 . The name “ parakoi ” is a combination of Greek “para-” (= analogous, alike) and “koi” (= the scientific name of koi ).

Morphological description. All the myxospores were mature, and no spore in vegetative stage was observed in this study. Mature spores were elongated and pyriform in the frontal view with pointed anterior end and rounded posterior end. Sutural view of the spores was not observed. The length and width of spores were 15.98 ± 0.78 (14.59–17.72) μm and 7.84 ± 0.78 (6.66–9.75) μm, respectively. Spore valves were smooth. Two pyriform polar capsules were equal in size, converging anteriorly, occupying over half of the spore body and measuring 8.72 ± 0.50 (7.76–9.92) μm in length and 3.03 ± 0.23 (2.63–3.56) μm in width. Polar filaments were coiled with 11 or 12 turns and perpendicularly situated to the longitudinal axis of the polar capsule. Intercapsular appendix, mucous envelope, iodinophilous vacuole and sutural edge marking were not observed ( Fig. 1 ).

Remarks. Among Myxobolus species described, M. parakoi sp. nov. closely resembled to M. koi , Myxobolus tanakai ( Kato et al., 2017) , Myxobolus orissae ( Haldar et al., 1996) , and Myxobolus longisporus ( Nie & Li, 1992) . However, the new taxon could be distinguished from M. koi described by Kudo (1919), which is the type material, by having a slightly longer spore (14.59–17.72 μm vs. 14–16 μm). Moreover, Myxobolus parakoi sp. nov. had longer spores than the populations of M. koi in other geographic distributions as shown in Table 1 ( Nakai 1926; Hoshina 1952; Crawshaw & Sweeting 1986; Yokoyama et al. 1997; Chen & Ma 1998; Camus & Griffin 2010; Liu 2014). The polar filament coils of the new species were more than that of referenced M. koi (11–12 vs. ≤10) ( Table 1 ).

The new species also resembled to M. tanakai by their elongated pyriform spores, but they also could be distinguished by following features: (1) the spores of M. tanakai had higher ratio of length to width compared with the new species; (2) the new species had more polar filament coils compared with M. tanakai (11–12 vs. 8–10) ( Table 1 ). Moreover, novel species and M. longisporus had also very similar spore morphometries. The difference was the number of the filament turns and the host species (and molecular). Also, M. orissae , M. longisporus and the species here described were found in different host species ( Table 1 ).

Figures

FIGURE S1. Regions of alignment of SSU rDNA gene sequences of M. koi, M. orissae, M. tanakai and Myxobolus parakoi sp. nov.. Matched sites are represented by dots. Regions are separated by vertical lines.