Redescription of deep-sea roughy

Hoplostethus (Leiogaster) melanopus

Phylum: Chordata

Class: Actinopterygii

Order: Beryciformes

Family: Trachichthyidae Bleeker, 1856

Hoplostethus (Leiogaster) melanopus Weber, 1913

Collection: Arabian Sea- 08°22′N, 76°09′E, 982 m, 12.10.2010 (FORV SS 281 St. 03); 08°31′N, 75°59′E, 1047 m, 12.12.2013 (FORV SS 321 St. 20); 08°05′N, 76°25′E, 1031 m, 12.01.2014 (FORV SS 322 St. 09); 08°28′N, 78°32′E, 1057 m, 15.01.2014 (FORV SS 322 St. 13); 08°32′N, 75°59′E, 1024 m, 04.11.2014 (FORV SS 331 St. 02)

Voucher No.: CMLRE R. C. No. 2810306, 3212007

Description: Body more plump than ovate, large sized, laterally compressed, maximum body depth 47–52 % of SL. Head large, length about 36–37 % of SL, occupied by deep muciferous cavities covered by a thin skin. Snout rounded with deep muciferous cavities, pre-dorsal length slightly greater than HL. A flat supra-clavicular spine, and a much stronger one at the angle of the preopercle. Eyes large, diameter 27–33% of HL. Mouth wide, terminal and obliquely angled, supramaxilla present. Small villiform teeth bands on jaws and on palatines. First dorsal fin with 4 striated spines and 15–16 soft rays, base length 34–39 % of SL. Anal fin with 2–3 spines and 10–11 soft rays, base length 13–19%of SL. Caudal fin forked with 6 procurrent spines in upper and lower lobes. Pectoral fins reach near end of anal base, with 19–20 rays, its length 33–38 % of SL. Pelvic fins with 1 spine and 6 rays. Body scales thin, ctenoid and deciduous, lateral line scales 26–30. 16–18 small keeled scales along midventral belly between pelvic and anal fins, forming row of un-developed scutes.

Biological association:

Remarks: Hoplostethus (L.) melanopus distributed in deeper waters at bathyal depths (>900 m) of the Arabian Sea and Andaman Sea.

Distribution: Northern Indian Ocean: off Socotra Island in the Arabian Sea, off Mentawai Island in the eastern equatorial Indian Ocean, southwest and east coast of India and Andaman Islands.

Distribution map:

Map showing locations of previous records (circle) and present record from Indian waters (square) of Hoplostethus (Leiogaster) melanopus

Identified by: Vinu Jacob

Publication: Vinu, J., Rajeeshkumar, M. P., Sumod, K. S., Meera, K. M., Hashim, M., Sanjeevan, V. N., & Sudhakar, M. (2017). Taxonomic clarification and re-description of two deep-sea roughies of genus Hoplostethus from the Indian Ocean. Marine Biodiversity47(2), 491-497.

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