Lucigadus Gilbert & Hubbs, 1920

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 237

Genus Lucigadus Gilbert & Hubbs, 1920

[No Japanese name]

Lucigadus Gilbert & Hubbs, 1920:553 (type species: Macrourus lucifer Smith & Radcliffe in Radcliffe, 1912, by original designation).

Diagnosis. Anus closer to pelvic-fin bases than to anal-fin origin; periproct moderately narrow; 2 dermal windows of light organ, one immediately anterior to anus, the other between pelvic-fin bases. Infraorbital ridge not connected with preopercular ridge, separated by distinct gap. Second spinous ray of first dorsal fin serrated along its leading edge. Ventral region of body positioned well forward so that gill membranes unite below orbits. Pelvic fin inserted below opercle. Snout smoothly rounded, lacking enlarged scutes. Head fully covered with small, unmodified scales. Chin barbel well developed. Teeth in narrow tapered bands in both jaws; premaxillary band extending beyond posterior edge of maxillary process. Body scales covered with short, erect, needle-like spinules; buttresses of spinules and reticulate structure absent. Grooved lateral line present. Branchiostegal rays 7. Body with silvery reflection when fresh. [Modified from Iwamoto & Anderson (1994), Iwamoto & Merrett (1997), and Iwamoto & Okamoto (2015).]

Remarks. Lucigadus was previously recognized as a subgenus of Ventrifossa Gilbert & Hubbs, 1920 (e.g., Iwamoto 1979, 1990), but Sazonov (1985) elevated this group to full generic rank. Most records of the genus were from tropical waters of the western Pacific or subtropical waters of the Southern Hemisphere ( Iwamoto & Okamoto 2015). According to Iwamoto & Merrett (1997) and Iwamoto & Okamoto (2015), Lucigadus currently comprises the following seven species: L. acrolophus Iwamoto & Merrett, 1997 known only from New Caledonia and the Norfolk Ridge; L. borealis Iwamoto & Okamoto, 2015 recently described from the Emperor Seamounts; L. lucifer (Smith & Radcliffe in Radcliffe, 1912) probably endemic to the Philippines; L. microlepis (G̹nther, 1878), a senior synonym of L. fasciatus ( Weber, 1913) and L. vittatus ( Weber, 1913) , widespread in the southwestern Pacific; L. nigromaculatus ( McCulloch, 1907) recorded from southeastern Australia, New Zealand, and off Chile; L. nigromarginatus (Smith & Radcliffe in Radcliffe, 1912) known from the Philippines, Indonesia, China, and Taiwan; and L. ori ( Smith, 1968) disjunctly distributed off the east coast of Africa and the west coast of Australia. A nominal species, Macruroplus potronus Pequeño, 1971 , was tentatively regarded as a junior synonym of L. nigromaculatus by Iwamoto & Okamoto (2015). Although the genus has not been recorded from Japanese waters, L. nigromarginatus is known from off the northeastern coast of Taiwan.

Sazonov (1985) considered this group to be closest to Malacocephalus G̹nther, 1862, but Lucigadus differs notably from the latter in that the ventral region of the body is positioned well forward so that the gill membranes unite below the orbits (vs. posterior to this level). They are further distinguished from each other by the combination of the lower jaw dentition (tapering band in Lucigadus vs. generally uniserial in Malacocephalus ) and the serration along the second spinous ray of the first dorsal fin [finely serrated along its leading edge vs. entirely smooth in most species (subgenus Malacocephalus )]. On the other hand, Lucigadus is similar in general appearance to Kuronezumia Iwamoto, 1974 , but readily differs in the absence of a reticulate structure on the body scales (vs. well developed in posterior parts of the unexposed portion) and its paler body coloration (vs. uniformly dark).