Molecular Taxonomy of Deep Sea Fishes Off the southern coast of India

Deep-sea fishes are one of the very interesting groups of animals that live in the darkness that is below the epipelagic or photic zone of the ocean. The deep-sea ecosystem is the largest habitat on Earth, covering 300 x106 km 2 that comprise about 63% of the earth’s surface, and is the main reservoir of global biodiversity (Smith et al., 2008). However, the deep-sea is the least productive part of the oceans, although some high biomass concentrations of fishes are found on the topographic features like seamounts, mid-oceanic ridges and continental slopes (Norse et al., 2012). Deep-sea fishes can be placed into mesopelagic, bathypelagic and benthopelagic categories, depending upon their depth preferences. Mesopelagic and bathypelagic species are true pelagic fishes, generally of small size even at their adult stage and unlikely to be exploited on a commercial scale (Valinassab et al., 2007). Lantern fishes (Myctophidae) and cyclothonids (Gonostomatidae) are the common mesopelagic fishes that live below the photic zone extending to 1000 m depth and they, along with bathypelagic fishes that live below 1000 m, are highly adapted to live in an environment where food is scarce. The deep-sea fishes from mesopelagic and bathypelagic depths have many unique and interesting adaptations for living in the extreme deep-sea environment