Thelohanellus nikolskii

Borz, eka, ak, Borkhanuddin, Muhammad Hafiz, Cech, abor, Kalm, Moln, an, ar, Hallett, Sascha L., Sz, Csaba & ekely, 2021, New data on Thelohanellus nikolskii Achmerov, 1955 (Myxosporea, Myxobolidae) a parasite of the common carp (Cyprinus carpio, L.): The actinospore stage, intrapiscine tissue preference and molecular sequence, International Journal for Parasitology: Parasites and Wildlife 15, pp. 112-119 : 114-115

3.2. Actinospore stage of Thelohanellus nikolskii in oligochaetes

Altogether 9452 oligochaetes were collected, belonging to the five most common oligochaete species in the Lake: Isochaetides michaelseni

114

Lastochin, 1936, Branchiura sowerbyi Beddard, 1892 , Nais sp. , Müller, 1774, Dero sp. Müller, 1774 and Aelosoma sp. Ehrenberg, 1828. Thirteen different actinospore morphotypes were identified from I. michaelseni , B. sowerbyi and Nais sp. However, no actinospores were found from Dero and Aelosoma spp. Actinospores could be assigned to the aurantiactinomyxon (5), neoactinomyxum (1), raabeia (2), synactinomyxon (1), and triactinomyxon (4) collective groups. Aurantiactinomyxon types were the most diverse form while triactinomyxon types were the most prevalent ( Table 3). One Nais sp. specimen out of the 1200 examined released an undescribed aurantiactinomyxon type actinospore ( Fig. 5 ), which corresponded to T. nikolskii based on the SSU rDNA sequence ( Fig. 6 ). Only these spores were the subject of this study and are described as follows:

Aurantiactinomyxon type

Description: Mature actinospores (n = 10) triangular to almost circular in apical view, diameter 10.3 (9.3–12.0) μm. Caudal processes of equal length, finger-like with rounded tips, and curved downwards, 14.6 (12.7–16.0) μm and 6.5 (5.3–7.3) μm wide, with largest span of 36.9 (33.5–40.2) μm. Polar capsules, three equally sized, round in apical view, 3.3 × 2.6 μm, with 3–4 rounds of polar tubule. Sporoplasm contains 8 germ cells.

Type host: Nais sp.

Type locality: Kis Balaton.

Prevalence of infection: 1/1200 (0.08%)

Site of infection: Body coelom.

Molecular data: An SSU rDNA amplicon of 477 bp was generated (GenBank accession # MT 569892). A BLAST search indicated highest similarity (99.8%) with T. nikolskii ( DQ 231156), differing in one nucleotide.

Remarks: Actinospores were found floating in the water of the cellwell plate in which the Nais worm was kept.

Differential diagnosis: This Aurantiactinomyxon type differs from other aurantiactinomyxons by having shorter caudal processes, about half to one-third of the length of known types. The caudal processes dimensions were most similar to the aurantiactinomyxon type ‘B2’ of Eszterbauer et al. (2006).

Figures

Fig. 5. Microphotograph of fresh, unstained actinospore of Aurantiactinomyxon type (AUM5) from Nais sp. Insert – apical view of spore with protruding polar capsules.

Fig. 6. Phylogenetic position of Thelohanellus nikolskii spores from the fins and scales of common carp based on SSU rDNA analysis by the Maximum Likelihood algorithm. Myxobolus cerebralis was used as the outgroup. Bootstrap values are given at the nodes. The scale-bar indicates the number of expected substitutions per site.