First Records of the Rare Giant Roughy <i>Hoplostethus grandperrini</i> (Teleostei: Trachichthyiformes) from Japan

Abstract

Two large specimens [310–476 mm standard length (SL)] of the genus Hoplostethus Cuvier in Cuvier and Valenciennes, 1829, collected from Iwate and Okinawa prefectures, Japan, were recently discovered and identified as Hoplostethus grandperrini Roberts and Gomon, 2012 on the basis of the following characteristics: large body size, exceeding 300 mm SL; abdominal scutes strong; pectoral fins light red; caudal-fin tip without black pigmentation; upper margin of eye almost horizontally level with lateral-line origin; predorsal scales not enlarged; fin spines moderately thickened; pectoral-fin tip not reaching anal-fin origin; anterior part of oral cavity, including underside of tongue, without black pigmentation; 15–17 pectoral-fin rays; 21 predorsal scales; and 13 or 14 abdominal scutes. Furthermore, a molecular phylogenetic analysis of a partial sequence of the mtDNA COI gene from one of the specimens placed it in the same clade as H. grandperrini previously recorded from Taiwan, with an uncorrected p-distance between both specimens of 0.19%. Hoplostethus grandperrini was originally described on the basis of two specimens collected off New Caledonia, with only one additional specimen having been reported (from southern Taiwan). The Japanese specimens are the first records of the species from Japan, the fourth and fifth specimens known, and the Iwate Prefecture specimen the northernmost record of the species.