The present study describes a new species, Thelohanellus muscularis n. sp. with light microscopy, histopathology and molecular analyses parasitizing the head muscles of Labeo rohita (Family Cyprinidae), commonly known as rohu is a native fresh water fish collected from Ranjit Sagar Wetland, Punjab, India has been described. The plasmodia were located in the head muscles in the opercular region and were round and whitish, 0.6-0.8 mm in size containing about 80-100 myxospores. The myxospores had a mean length of 9.20 ± 0.28 µm, width 4.0 ± 0.15 µm, mean length of polar capsule 5.85 ± 0.08 µm, width 3.10 ± 0.11 µm. The 18S rDNA nucleotide with 900 bp of T. muscularis n. sp. (accession number KT387308) clustered phylogenetically with other myxozoan parasites with the species most closely related to it is T. filli (KR340464), T. sp. RA (KR423868) and T. jiroveci (KJ476885) with 99% homogeneity. The prevalence of infection was 25%. Phylogenetic analyses elucidated relationship of the newly described Thelohanellus muscularis to other Thelohanellus species and supported its position of an independent species.
Key words: 18S rDNA; muscles; Phylogenetic analysis; Labeo rohita; India.