Morpho-molecular characterisation of two new and two previously reported species of Acanthogyrus (Acanthogyrus: Quadrigyridae) from freshwater fishes in India.

Of the total 47 species in the subgenus Acanthosentis, 43 have been reported from the freshwater fishes of Asia. Amin et al. (2017) provided a key to the 23 species of the genus Acanthogyrus reported from the Indian subcontinent. The present study reports two new species: Acanthogyrus bispinosa n. sp. and A. garciai n. sp. from Cirrhinus mrigala Hamilton and Labeo calbasu Hamilton, respectively, and two previously described species: A. golvani Gupta and Jain, 1980 and A. hereterospinus Khan and Bilqees, 1990 from L. rohita Hamilton and L. catla Hamilton, respectively. A. bispinosa n. sp. comprises 3 circles of 6 proboscis hooks each. Trunk spines in A. bispinosa n. sp are divided into two groups: anterior and posterior separated by unarmed region, which has not been previously reported in the subgenus. Anterior spines are present in 7-8 and 7-10 circles in females and males, respectively, whereas posterior spines are in 23-28 and 31-38 circles in males and females, respectively. A. garciai n. sp. comprises 3 circles of 6-8 hooks each and a single set of trunk spines is present in A. garciai n. sp., comprising 35-42 and 25-45 circles in males and females, respectively. All four species were also characterised based on the 18S, 28S, and ITS1-5.8S-ITS2 rRNA molecular markers. The Bayesian inference tree generated based on these markers showed distinct identities of all the species, with a significant molecular divergence, ranging from 3.2 to 53.6%.