Supplemental description and molecular characterization of Myxobolus miyarii Kudo, 1919 (Myxosporea: Myxobolidae) infecting intestine of Amur catfish (Silurus asotus)

Abstract

Myxobolus miyairii Kudo, 1919 was first reported from the intestines of the Amur catfish (Silurus asotus) in Japan and then in China and Russia, but with incomplete description. During the investigation of fish myxosporean diversity in Poyang Lake, the biggest lake along the Yangtze River, China, two Amur catfish highly infected with M. miyairii in the intestine wall were sampled. So, the complete description of this species with morphological and molecular data was presented here. A large number of whitish, round or ellipsoidal pseudocysts 0.32-0.78 mm in diameter could be found in the external intestinal wall after dissecting the infected fish. Mature spores of M. miyairii were elongated and ellipsoidal in the frontal view and narrow fusiform in the lateral view, with a slightly pointed anterior end and a bluntly rounded posterior end and measured 13.3 ± 0.49 (12.5-14.7) μm × 6.6 ± 0.27 (6.2-7.4) μm × 5.0 ± 0.26 (4.4-5.7) μm in size. Spore surface was smooth and two spore valves symmetrical, with a thin and straight sutural ridge. Interestingly, two types of caudal appendage (single or bifurcated) were occasionally present on the posterior end of some spores which has not previously been reported. The two equal pyriform polar capsules measured 6.5 ± 0.30 (6.2-7.5) μm long and 1.9 ± 0.14 (1.5-2.3) μm wide and situated at the anterior end of the spore. Polar filaments coiled with eight to nine turns, perpendicularly to the longitudinal axis of the polar capsules. Histopathological analysis showed that the plasmodium developed in the circular muscle layer of intestinal wall of Amur catfish, but no obvious inflammatory responses were observed. Phylogenetic analysis based on the partial 18S small subunit ribosomal DNA sequences indicates that M. miyairii cluster within a clade of Siluriforme-infecting Henneguya species with the support of a high bootstrap value, but also evolutionarily independent from the Henneguya clade infecting the epithelium of fish of the Ictaluridae family. Additionally, Myxobolus species reported with caudal processes dispersed within the Henneguya-Myxobolus clade.

Morphological and molecular characterization of Myxobolus sheyangensis n. sp. (Myxosporea: Myxobolidae) with intralamellar sporulation in allogynogenetic gibel carp, Carassius auratus gibelio (Bloch) in China

“…From another perspective, all species with taper anterior end of spores (all species with this character within this clade) were genetically separated from those with round anterior end of spore, like Myxobolus hearti, Myxobolus oralis, Myxobolus nielii, and M. turpisrotundus. This genetic affinity of Myxobolus species based on spore morphology was also previously reported (Zhang et al 2010a;Liu et al 2016). Moreover, the present analysis indicated that phylogenetic relationships of gill-infecting Myxobolus of cyprinid fish showed a distinct geographical pattern, synergistic with the host affinity.…”

Myxobolus marajoensis sp. n. (Myxosporea: Myxobolidae), parasite of the freshwater catfish Rhamdia quelen from the Brazilian Amazon region

“…The morphology of this species is similar to that of M. miyarii (LIU et al, 2016) and M. cunhai (PENIDO, 1927), given the pyriform shape of the spores, which are distinct from the ovoid spores of M. pangasii (MOLNÁR et al, 2006), the elliptical spores of M. hakyi Baska et al (2009) and M. gayerae Molnár et al (2007), and the spherical spores of M. bivacuolatus (NARASIMHAMURTI & KALAVATI, 1986) (Table 1).…”

“…A number of other Myxobolus species found in siluriforms have been described based on the analysis of the 18S rDNA gene, including M. myarii, found in the S. asotus by Liu et al (2016). Using this gene, Baska et al (2009) confirmed the presence of M. hakyi in the epidermis of the P. hypophthalmus, while Molnár et al (2006) found M. pangasii infecting its spleen.…”

“…In comparison with the Myxobolus species found in the intestinal tracts of other catfish species, Myxobolus marajoensis sp. n. is closest in size to M. cunhai, which infects the catfish P. clarias maculatus (PENIDO, 1927), M. bivacuolatus and M. pangasii, found in Pangasius hypophthalmus (MOLNÁR et al, 2006;BASKA et al, 2009), and M. miyarii, a parasite of S. asotus (LIU et al, 2016) (Table 1). Myxobolus marajoensis sp.…”

“…In the catfish (Siluriformes), these parasites have been found infecting a variety of organs, such as the gills of the bandit corydoras, Corydoras melini Lönnberg andRendahl, 1930 (MATHEWS et al, 2016) and the jau, Zungaro jahu Ihering, 1898 (ADRIANO et al, 2009), the intestine of the Amur catfish Silurus asotus Linnaeus, 1758(LIU et al, 2016 and the Philippine catfish Clarias batrachus Linnaeus, 1758(NARASIMHAMURTI & KALAVATI, 1986, the intestine and gills of the European chub, Leuciscus cephalus Linnaeus, 1758 (MOLNÁR et al, 2007) and the spleen of the striped catfish, Pangasianodon hypophthalmus Sauvage, 1878 (BASKA et al, 2009). …”