Ichthyapus acutirostris Brisout de Barneville

John E. McCosker & John E. Randall, 2005, Notes on the snake eels of the genera Apterichtus and Ichthyapus (Anguilliformes: Ophichthidae) of the Central and South Pacific, with the description of a new species., Zootaxa 800, pp. 1-11 : 7-9

[[ Ichthyapus acutirostris Brisout de Barneville ]]

Comments on Easter Island and Hawaiian species of Ichthyapus

In 1975 we (Randall and McCosker, 1975) provisionally identified Easter Island specimens of Ichthyapus as I. vulturis (Weber & de Beaufort 1916) and included Caecula (Sphagebranchus) platyrhyncha Gosline 1951 in its synonymy. We did so because they appeared to be identical in morphometry and intermediate in their vertebral and cephalic pore conditions. We surmised that the preopercular condition of four specimens from Hawaii and Kure (2 had 3 pores and 2 had 4 pores) was normal variation for that character. We were wrong. After examining additional specimens from Hawaii and elsewhere in the Pacific, we have determined that two species exist in the Hawaiian archipelago and that the Easter Island population is I. acutirostris Brisout de Barneville (1847) (illustrations of I. acutirostris appear in Blache & Bauchot 1972 and in Randall & McCosker 1975). We now recognize Hawaiian Ichthyapus to include I. vulturis (Fig. 3) (which have a comparatively larger eye, 124-134 total vertebrae, MVF=47.1-130.1, and 4 preopercular pores, n=20) and I. platyrhynchus (Figs. 3-4) (which have a smaller eye, 120-128 total vertebrae, MVF=48.6-124, and 3 preopercular pores, n=17).

McCosker (2004: 171-173) recently proposed that Ichthyapus acutirostris , which had been described on the basis of two specimens (only one is extant) from "Haute-Mer, Océan équatorial," is the correct identity of specimens captured in Japan (Hatooka et al., 1995). He examined the extant syntype of I. acutirostris , compared the larger of Hatooka's 2 specimens to the Easter Island material, and found them all to be conspecific. In that the collector of the holotype of I. acutirostris (Monsieur Paul-Charles-Alexandre-Léonard Rang, 1793-1843, a French malacologist) never visited the South Pacific (few if any collections had been made at or near Easter Island before the 20th century) but had traveled to Japan (aboard the Levant after 1836), McCosker concluded that the remaining type specimen of I. acutirostris was probably collected from Japan.

The collection of additional Easter Island specimens of Ichthyapus acutirostris as well as a specimen from Pitcairn Island (BPBM 11898, 427 mm) has allowed us to provide an expanded description of the morphometrics and vertebral counts of I. acutirostris (Table 3). All specimens have 3 preopercular pores, 5 temporal pores, and 5 lower jaw pores.

Material examined of Ichthyapus acutirostris : MNHN 2119, 228 mm, locality unknown, the extant syntype . From Japan: OMNH-P 5239, 531 mm . From Easter Island: BPBM 6589, 235 mm ; BPBM 6590, 2(218-222 mm) ; BPBM 6591, 246 mm ; BPBM 39203, 2(243-298 mm) ; LACM 6560, 5(281-402 mm) . From Pitcairn Island: BPBM 11898, 427 mm .