Myxobolus rewensis Srivastava (1979)

Sz, Csaba, ekely, Ghosh, Subarna, Borz, eka, ak, Goswami, Urvashi, alm, Moln, an, ar & Cech, abor, 2021, The occurrence of known Myxobolus and Thelohanellus species (Myxozoa, Myxosporea) from Indian major carps with the description of Myxobolus bandyopadhyayi n. sp. in West Bengal, International Journal for Parasitology: Parasites and Wildlife 16, pp. 18-25 : 23-24

3.5. Myxobolus rewensis Srivastava (1979) ( Figs. 14–16)

Three out of the 11 mrigal specimens purchased on the fish market were infected with small ellipsoidal-shaped plasmodia reaching a size of 1–2.2 mm in length and 0.5–0.7 mm in width, which were located in the fins between two fin rays close to the base of the fin ( Fig. 14). The plasmodia contained 2,000 to 10,000 spores.

Spores ( Figs. 15 and 16 ) small sized, ellipsoidal in frontal view and lemon shaped in sutural view, 8.8 ± 0.16 (8.5–9.1) long, 7.3 ± 0.27 (6.8–9.7) wide and 5.2 ± 0.22 (5–5.4) thick. Two oval polar capsules equal, 3.8 ± 0.19 (3.4–4) long, 2.1 ± 0.14 (2.1–2.3) wide. Polar tubules not seen. Nuclei of the polar capsules distinct, measuring 1.7 × 0.6 on average. Spore with a rounded, about 0.9–1 thick intercapsular appendix in which a bright globule with a diameter of 0.8 is located. Sporoplasm nuclei indiscernible. A small iodinophilous vacuole present in the sporoplasm. Mucous envelope not found. The spore wall (which corresponds to the emerging collar of the suture) has 8 sutural edge markings. Its thickness 0.66 ± 0.05 (0.6–0.7).

Host: Mrigal Cyrrhinus mrigala Hamilton.

Locality: East Kolkata Wetlands 22.5263 ◦ N 88.4716 ◦ E (District South 24 parganas, Baranagar Block) .

Site of infection: Fins.

Type material: Photo-types and histological preparations were deposited in the parasitological collection of the Zoological Department, Hungarian Natural History Museum, Budapest, Coll. No. HNHM-PAR-72081. The ssrDNA sequence of M. rewensis was deposited in the GenBank under accession number MZ230381 .

Prevalence of infection: 3 specimens from 10 fish.

Molecular data: ssrDNA sequence of Myxobolus rewensis was a sister group of Myxobolus dermiscalis showing a 91.9% similarity. There was also a 90.1% similarity to a Thelohanellus sp. sample ( KM 401440) from the skin and gill arch of rohu.

Remarks: The Myxobolus species found by us resembles Myxobolus rewensis , differing only in two characteristics. Plasmodia found by us were located in the fin of mrigal, while Srivastava (1979) described the

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infection from the scales. Both spores found by us and spores of M. rewensis have a relatively large intercapsular appendix, but we were able to observe a characteristic bright nodule inside the appendix. Four other morphologically similar species ( Table 2, M. shetti Seenappa and Manohar, 1981 and M. vanivilasae Seenappa and Manohar, 1980 from mrigal; M. dermatis Haldar et al., 1981 and M. rohitae Haldar et al., 1983 from rohu) have been described from labeonid fishes ( Seenappa and Manohar, 1980, 1981; Haldar et al., 1981, 1983). However, the plasmodia of the latter species develop either in the scales or in the gills. Myxobolus dermatis and M. rohitae were described from rohu which is phylogenetically relatively far from mrigal ( Khedkar et al., 2014; Chakraborty and Ghosh, 2014). Among the species described from mrigal, M. vanivilasae differed from M. rewensis in spore morphology having relatively small polar capsules, while the spores of M. shetti have only a small indistinct intercapsular appendix. Despite the different location and the small globule found in the intercapsular appendix, we regard the spores found by us as belonging to M. rewensis Srivastava (1979) until organ and tissue specificity can be studied in more detail.

Figures

Fig. 15. Spores of M. rewensis from the fin of mrigal. Arrow is indicating the characteristic globule inside the intercapsular appendix. Mount picture. Bar = 10 μm.

Fig. 16. Schematic drawing of spore of M. rewensis, a: frontal view, b: sutural view. Bar = 10 μm.