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

Apterichtus orientalis Machida and Ohta 1994

Table 1

Apterichtus orientalis Machida and Ohta 1994:1 , Figs. 2–4 (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.

Figures

FIGURE 2. Underwater photograph of living Apterichtus flavicaudus, taken by J. Randall at 15 m, Makua, O’ahu, Hawai’i.

FIGURE 3. Underwater photograph of living Apterichtus caecus, taken by P. Gomes at night at 14 m, Funchal, Madeira.

FIGURE 4. A. Anterior nostril without a tube. B. Anterior nostril within a tube.