Apterichtus orientalis Machida and Ohta 1994

Hibino, Yusuke, 2015, A review of the finless snake eels of the genus Apterichtus (Anguilliformes: Ophichthidae), with the description of five new species, Zootaxa 3941 (1), pp. 49-78: 75

publication ID


publication LSID


persistent identifier


treatment provided by


scientific name

Apterichtus orientalis Machida and Ohta 1994


Apterichtus orientalis Machida and Ohta 1994 

Table 1

Apterichtus orientalis Machida and Ohta 1994: 1  , Figs. 2–4View FIGURE 2View FIGURE 3View FIGURE 4. A (type locality Southeast of Kii Peninsula, Wakayama Prefecture, Japan, holotype BSKU 81631).

Diagnosis. An elongate species with: tail 1.8, head 12–14, and body depth 53–55 in total length; 3 preopercular pores and 7 pores in supratemporal canal; teeth conical, uniserial, 9 in ethmoidal region, 1 tooth on vomer; body coloration uniform pale yellow with small brownish dots, lighter ventrally; and MVF 54–132, total vertebrae 131–133 (n= 2).

Size. The largest specimen examined is 443 mm, sex unknown. The holotype (318 mm TL) is a female with ripened eggs.

Distribution. Known from the holotype, which was collected from Kii Peninsula, central Honshu Island, Japan by dredge over sand and mud at 79–81 m depth, and a specimen from Kochi Prefecture, Shikoku Island, Japan.

Remarks. This species has more cephalic pores than any Apterichtus  other than A. monodi  , A. hatookai  and A. jeffwilliamsi  . It differs from A. monodi  by having fewer vertebrae (131–133 vs. 142–151) and from A. hatookai  and A. jeffwilliamsi  by having 3 rather than 4 preopercular pores. The holotype of A. orientalis  has 4 right and 3 left preopercular pores. Its other cephalic pores are symmetrical in location and number. An additional pore exists on both sides before the middle of the eye about midway to the base of the anterior nostril. Machida and Ohta (1994) infer that the posterior right mandibular pore is located in the preopercular canal rather than the mandibular canal, explaining the 5 + 4 (left) and 6 + 3 (right) condition. The second known specimen has 6 + 3 pores on both sides, which appears to be the normal condition for this species. Machida and Ohta (1994) also reported that the holotype of A. orientalis  has no teeth on its vomer. We examined the holotype and found it to have a prominent hole in the prevomerine region (the tooth was probably lost). The second specimen has a relatively large vomerine tooth.

Material examined. BSKU 81631, holotype, 318 mm, Southwest of Kii Peninsula, Wakayama Prefecture, Japan (33 ° 26.4 'N, 135 ° 43.8 'E to 33 ° 26.2 'N, 135 ° 44.3 'E), 79– 81 m. NSMT-P 115430, 443 mm, Kashiwajima, Kochi Prefecture, Japan, depth unknown.


Kochi University














Apterichtus orientalis Machida and Ohta 1994

Hibino, Yusuke 2015

Apterichtus orientalis

Machida 1994: 1