Apterichtus equatorialis ( Myers & Wade 1941 )

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 : 60

Apterichtus equatorialis ( Myers & Wade 1941)

Table 1

Caecula equatorialis Myers & Wade 1941:75 , Pl. 11 (type locality North of Barrington Island, Galápagos Islands, holotype LACM 21723).

Caecula (Sphagebranchus) gymnocelus Böhlke 1953:325 , Fig. 1 (type locality East of Isla Angel de la Guarda, Gulf of California, Mexico, holotype SU 17589).

Apterichtus equatorialis: McCosker 1977:66 .

Diagnosis. An elongate species with: tail 1.8–2.0, head 11–16, and body depth 43–50 in total length; 3 preopercular pores and 3 pores in supratemporal canal; teeth conical, uniserial on jaws and vomer; 4–5 vomerine teeth; in preservative, body coloration uniform light tan, overlain with fine sparse brown speckling, branchial region and top of head with irregular small dark spots and blotches; and MVF 59–138, total vertebrae 132–146 (n=9).

Size. The largest specimen examined is 312 mm, a male.

Distribution. From the eastern tropical Pacific between the Gulf of California and the Galápagos, captured by rotenone, dredge and trawl in 10–134 m over sand and mud bottoms.

Remarks. The holotype was damaged during its capture by dredge and only the head and trunk remain. Extrapolation of that measurement (93 mm) would indicate that the specimen was ca. 185–210 mm in total length. Few photographs of this species exist; a color photograph of a live individual and a freshly captured specimen appear in Allen & Robertson (1994:50–51). The number of vertebrae of our specimens of Apterichtus equatorialis appears to be quite broad within its range. Although we have only 8 countable specimens (the holotype has been severed and other specimens are too minute and poorly preserved to be counted), it appears that northern specimens have significantly fewer vertebrae. Those from Baja California have 132, 132, 135, and 136, from Panama has 139, from Galápagos have 140, 141, and the specimen from 03°15’S, 80°19’W has 146. We are unable to find any other differences between those specimens.

Material examined. 14 specimens, 60–312 mm TL, including the holotype ( LACM 21723 ex AHF 12, head and trunk region only), Santa Fe Id. (Barrington Id.), Galápagos Is. (00o43'S, 90o01'W), 134 m. SU 17589, holotype of Caecula gymnocelus , 217 mm, Angel de la Guarda Island, Gulf of California, Mexico (29o21'N, 113o19'W), 106– 113 m. SU 17590, 240 mm, paratype of C. gymnocelus , collected with the holotype. LACM 23581 (ex AHF 1057–40), 2(72–75 mm), Angel de la Guarda Id., Gulf of California, Mexico (29o21'N, 113o19'W), 93 m. LACM 23852 (ex AHF 1113–40), 2(115-282 mm), NE of Espiritu Santo Is., Gulf of California, Mexico (24°32’N, 110°20’W), 106 m. LACM 23853 (ex AHF 1037-40), 2(270–312 mm), Boca de la Trinidad, Gulf of California, Mexico (23°38’N, 109°30’W), 93– 97 m. ANSP 117436, 272 mm, Ecuador (03°15’S, 80°19’W), 32 m. LACM 43673, 4(60–64 mm), Galápagos, Darwin Id. (01°40’N, 92°01’W), 46 m.

Figures

FIGURE 1. Underwater photograph of living Apterichtus hatookai, taken by J. Shibata at 7 m at Shikohu Island, Japan. Courtesy of Ichthyological Society of Japan