茨城県沖で採集された日本初記録のウミヘビ科魚類Ophichthus longicorpusアズキウミヘビ（新称）

抄録

A single specimen (440 mm in total length) of the genus Ophichthus Ahl, 1789 (Anguilliformes: Ophichthidae), captured during a bottom trawl survey at a depth of 351– 353 m off Ibaraki Prefecture, Pacific coast of northern Japan, was identified as Ophichthus longicorpus Vo and Ho, 2021, due to the following combination of characters: 29 predorsal and 162 total vertebrae; head length 8.4% of total length; dorsal fin origin situated at 5.0 pectoral fin length (1.2 head length) behind head; pre-dorsal length 19.5% of total length; pectoral fin length 25.6% of head length; pectoral-fin tip slightly pointed; and body without spots and bands. The present specimen represents the second record of the species since its original description, based on Vietnamese specimens, and adds considerable northern and eastern extensions to its known distribution. On the other hand, a number of morphological differences were apparent between the Japanese (n = 1) and Vietnamese (n = 13) specimens, including differences in cephalic sensory pore numbers (1 + 3 = 4 in the supraorbital series and 5 in the mandibular series in the former vs. 1 + 4 = 5 and 6 in the latter), and anus position (somewhat anterior to the middle between the snout tip and tail tip vs. almost in middle). The differences are presently considered to represent intraspecific variations, due to the wide range of morphological variations recorded in other species of Ophichthus, although further taxonomic considerations may be in order pending the availability of a greater number of widely-distributed specimens. The new standard Japanese name “Azuki-umihebi” is proposed for the species, referring to its reddish-brown body coloration.