Categories identification and morphological characteristics on larvae and juveniles in genus Diogenichthys Bolin,1939 and their classification retrieval

What is it about?

Based on the analysis of Myctophum Rafinesque, 1810 larvae and juveniles samples collected during the oceanographical expedition cruises in central and western tropical Pacific during April 1978 to June 1979 and in Kuroshio extension regions of the East China Sea during April 1984 to June 1986, this paper identified the larvae and juveniles of Myctophum spinosum (Steindachner, 1867), M. nitidulum Garman, 1899, M. asperum Richardson, 1845, M. punctatum Rafinesque, 1818, M. aurolaternatum Garman, 1899, M. orientale (Gilbert, 1913), M. obtusirostris Tåning, 1928 and Myctophum sp., described their ontogenic morphological characteristics in detail. Combined with the other three Myctophum species, M. lychnobium, M. selenops and M. brachygnathum that distributed in China with morphological characteristics already known, the identification key for these eleven species has been established.The result conveyed that all but M. aurolaternatum larvae and juveniles in genus Diogenichthys observed with enlarged fan-shaped pectoral fins. The head somewhat flat was in a triangular shape with non spherical eyes on elongate stalks or with well developed conical choroid mass. Pigments were distributed on the jaws, isthmus, opercle, branchiostegal membrance and pectoral fin base. Pigment series on lateral gut evenly distributed on trailing section, except heavier near terminus. The jaws were full of sharp teeth. A single adipose fin was found on the back behind the dorsal fin. All these were the common characteristics of larvae and juveniles in genus Diogenichthys. M. aurolaternatum larvae was with unique morphological characteristics features: very flat head, eyes small on distinct elongate stalks, and with straight gut trailing at midbody and extending to well beyond caudal fin. The shape of the choroid tissue or whether they owns elongate stalks to the eyes; whether there were melanophores at the anterior tip of the lower or upper jaws; pigment pattern on the pectoral fin base, between the pectoral fin rays and on lateral gut; whether there was melanophores distributed on the tip of tail, the trailing edge of the anal fin and adipose fin were the distinct categories identification and morphological characteristics on larvae and juveniles in genus Myctophum.

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