Validity of Heteronarce prabhui Talwar, 1981 and Narke impennis (Annandale, 1909) (Pisces: Narkidae) off Visakhapatnam, central-eastern coast of India

Sleeper rays of family Narkidae are represented in demersal shrimp trawl by-catches of Visakhapatnam (Lat. 17°01' N to 19°22' N; Long. 83°23' E to 85°14' E), in the central-eastern coast of India. A total of 158 specimens belonging to two genera Heteronarce Regan, 1921 (three species) and Narke Kaup, 1826 (two species) were collected from July 2015 to March 2018. These species are often misidentified in the catches due to several overlapping characters. Multivariate analysis including Principal Component Analysis (PCA) has been carried out to identify distinguishing characters to help in differentiating these species. In addition, DNA barcodes were generated for two species in genus Narke, and a phylogenetic tree was constructed with reference sequences. Molecular phylogenetic results were assessed and integrated with sound morphological evidence. Thus, the present paper helps in clarifying taxonomic ambiguities by providing diagnostic characteristics, comparing morphometric data of closely related species, and discussing the validity of Heteronarce prabhui Talwar, 1981 and Narke impennis (Annandale, 1909). In the present study,   H. prabhui represents the first report from the east coast of India; barcode sequences were generated for the first time for N. impennis. Additionally, Cytochrome C Oxidase I (COI) gene sequences were generated for the first time from the Indian waters for  N. dipterygia (Bloch and Schneider, 1801).