First Morphological Description and the Distribution of Ophisurus macrorhynchos (Anguilliformes: Ophichthidae) Leptocephalus Collected from Southeastern Waters of Jeju Island

Abstract

Seventeen specimens of leptocephali [9.8-44.5 mm total length (TL)], of the family Ophichthidae, were collected from southeastern waters off Jeju Island and the Korea-Japan intermediate zone, and identified by means of morphology and genetics. These specimens were identified as belonging to the subfamily Ophichthinae based on various combinations of morphological characters: 211-215 total myomeres; 7 gut swellings; 2 liver lobes connected with the gall bladder on the second lobe; 6-7 postanal pigments present from anus to caudal margin. An analysis of the partial 12S rRNA sequences (849 base pairs) of mitochondrial DNA showed that our specimens must be Ophisurus macrorhynchos because their sequences were concordant with those of the adult O. macrorhynchos (genetic distance = 0.000). Furthermore, their total myomeres were consistent with those of the O. macrorhynchos adult. This is the first time that the morphological characteristics of O. macrorhynchos leptocephali have been described for Korean waters, and we suggest diagnostic characteristics for the genus Ophisurus leptocephali. We hypothesize that one of the spawning grounds of O. macrorhynchos is located in the southeastern part of Jeju Island.

Genetic identification of eggs from four species of Ophichthidae and Congridae (Anguilliformes) in the northern East China Sea

“…Fortunately, adults and leptocephali of O . macrorhynchos were found in the East China Sea [ 7 , 34 , 35 ]. The eggs were thus determined to be O .…”

“…The distribution ranges varied greatly by taxon. The leptocephali of Ophisurus macrorhynchos (August, 9.8–44.5 mm total length [TL]) [ 7 ] and Echelus uropterus (July-October, 14.6–68 mm TL) [ 21 ] were found only where the eggs were detected (Figs 6 and 7 ). Leptocephali of the Congridae have been collected in several widely distributed areas, including where the eggs were detected.…”

“…Leptocephali of O . macrorhynchos (August 2013 and 2014, 9.8–44.5 mm TL) [ 7 ] are shown with blue diamonds. The other markings indicate surveys for fish eggs and/or larvae, but with no catches for these of O .…”

“…To compare the distributions of Ophichthidae and Congridae eggs analyzed in this study with those of eggs and leptocephali from literature, we collected geographical information for eggs and larvae of the species: Ophisurus macrorhynchos , Echelus uropterus , Ariosoma majus (known previously as Ariosoma sp.7), and Gnathophis heterognathos . Details of the surveys from the references [ 6 , 7 , 18 , 21 , 29 – 32 ] are described in Table 5 . The distributions of each species of eggs collected in this study and leptocephali and ocean currents were marked on maps drawn using Ocean Data View [ 33 ].…”

“…Analysis of newly hatched preleptocephali and small leptocephali increases the accuracy of locating spawning areas [ 3 – 5 ]. Small leptocephali of the Ophichthidae and Congridae are found near the continental shelf and edge of the shelf break in the East China Sea and over the continental shelf of the southern Korean Peninsula [ 6 , 7 ]. However, the presence of eggs, representing spawning events, has not yet been reported in these areas.…”