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Identification of a new myxosporean parasite Thelohanellus indiana n. sp. (Myxosporea: Myxobolidae) isolated from three major organs of goldfish, Carassius auratus L. highlighted with its morphological and SSU rDNA sequence based molecular description

Saha, Mandira, Bandyopadhyay, Probir Kumar
Microbial pathogenesis 2018 v.122 pp. 191-199
Carassius auratus, Myxobolidae, aquaculture, genes, goldfish, molecular systematics, monophyly, mortality, new species, nucleotide sequences, ornamental fish, parasites, ribosomal DNA, ribosomal RNA, scanning electron microscopes, spores, India
Fish mortality and poor growth in surviving fish contribute substantial losses to the ornamental fish farms of India and revealed an infection of a new myxosporidian parasite Thelohanellus indiana n. sp. which has become one of the most important limiting factors for successful aquaculture management. The parasite infects Carassius auratus, an Indian goldfish, described on the basis of myxospores morphology and amplification of a part of 18 S rDNA gene. Three major attaching site of fish body have been explored for showing the location of attachment for the parasites. The whitish cysts of the parasites are about 2.5–3.5 mm contains large amount of lemon shaped mature myxospores measuring 12.1–15.2 (13.8) × 7.5–8.8 (8) μm. A single round or elliptical polar capsule located only at the anterior pole of the spore having 6.2–7.2 (6.8) × 3.3–4.7 (4.0) μm in diameter. The morphological characters have been assessed by both the light and scanning electron microscope. The most differentiating feature from closely related species was carried out by morpho-taxonomic affinities with previously described species which are tremendously supported by molecular taxonomy by partial sequencing of the 18 S rDNA gene resulted in a total of 2101 bp fragment of newly obtained SSU rRNA gene sequence of the new species which exhibit 79–91% homogeneity with other closely related species available in GenBank. The BLAST search of Thelohanellus sp. did not matches with any available sequences in GenBank and the phylogenetic analysis revealed that the novel species were sister to T. habibpuri and T. caudatus, in the Thelohanellus clade and form a closest neighboring branch as a subclade in phylogenetic tree from which the new Thelohanellus parasite is being placed. Both the branches are originating from monophyletic clade that are strongly supported by bootstrap values which indicate clearly about independent position of T. indiana n. sp.