Dermal fibroma in a tawny nurse shark, Nebrius ferrugineus (Lesson, 1831)

Sharks are ecologically and economically significant group of fishes which invite both domestic as well as international demand. The tawny nurse shark, Nebrius ferrugineus, is a commonly occurring species in the landings in India forming about 1.4% of the shark catches in the region. Besides, N. ferrugineus is one among the shark species which are listed as ‘vulnerable’ by the International Union for Conservation of Nature (IUCN) in their Global Red List assessment (Pillans, 2003). Tumours in both captive and feral fishes are not uncommon and most of the tumours that occur in terrestrial animals have been reported in fishes. Presently, there is a growing interest to study fish neoplasms as a means of detecting injurious agents in the environment. Furthermore, the usefulness of fish as a model for studying human diseases including neoplasms has also prompted researchers to pay much interest in unravelling tumorigenesis in fish (Schmale, Nairn, & Winn, 2007). While there are no systematic studies on fish neoplasms from India, some of the reported tumours include odontoma in pickhandle barracuda, Sphyraena jello (Singaravel et al., 2017), cutaneous myxoma in blackfin sea catfish (Singaravel, Gopalakrishnan, Vijayakumar, & Raja, 2015), and lipoma in a gold fish (Sood et al., 2017). Fibromas are benign neoplasms of mesenchymal origin composed of fibrous connective tissue. Different types of mesenchymal tumours have been reported in many fish species which include but not limited to fibrosarcoma in Goldfish (Ahmed, 1980) and red band parrot fish (Rezaie, Dezfuly, & Peyghan, 2017)