Notes on Hawaiian Snake Eels (Pisces: Ophichthidae), with Comments on Ophichthus bonaparti

Abstract

The 22 ophichthid eel species of the Hawaiian Islands (including Johnston and the Northwestern Hawaiian Islands) are reviewed, and a key to their identification is provided. New Hawaiian records of Indo-Pacific species include Callechelys catostoma and Ophichthus bonaparti. Callechelys lutea is reported from Johnston Island. Hawaiian and Johnston Island ophichthid species comprise: Apterichtus flavicaudus, Brachysomophis crocodilinus, B. henshawi, Callechelys catostoma, C. lutea, Cirrhimuraena playfairii, Ichthyapus vulturis, Leiuranus semi-cinctus, Muraenichthys schultzei, Myrichthys colubrinus, M. magnificus, Ophichthus bonaparti, O. erabo, O. kunaloa, O. polyophthalmus, Phaenomonas cooperae, Phyllophichthus xenodontus, Schismorhynchus labialis, Schultzidia johnstonensis, Scolecenchelys cookei, S. gymnota, and S. puhioilo. Additional data are provided for the rare deep-water species Ophichthus kunaloa. The following synonymies are proposed: Ophisurus chrysospilos Bleeker, Poecilocephalus markworti Kaup, Ophichthys episcopus Castelnau, and Ophichthys garretti Günther = Ophichthus bonaparti (Kaup); and Ophichthus retifer Fowler = Ophichthus erabo (Jordan & Snyder). The endemism and distribution of Hawaiian and Johnston Island ophichthids (22.7%) are discussed and compared with those of muraenid eels. Vertebral formulas are provided for all species to facilitate the identification of leptocephali.

The snake eels and worm eels (family Ophichthidae) of the Hawaiian Archipelago (including Johnston Island and the Northwestern Hawaiian Islands) comprise 22 species distributed among 14 genera, making them the sixth most speciose family of Hawaiian fishes. Most species are pale, inhabit sand and mud bottoms, and are rarely encountered, but some are strikingly marked and can be seen at the surface at night, particularly during breeding periods. They, along with the morays, have intrigued students of Hawaiian eels and often appear in Hawaiian legend and lore (Pukui 1902, Colum 1937, McCosker 1979). Although inadequately sampled, the eel fauna of Johnston Island contains the most speciose fish family (Muraenidae, with 30 species), and the ophichthids are among the top 10 (Kosaki et al. 1991). The actual abundance of ophichthids throughout their range, however, is underestimated as a result of their burrowing behavior, and the ability to characterize many of these forms, many lacking coloration and others entirely devoid of fins, is difficult at best. Vertebral numbers appear to be the most useful character to differentiate populations and species of these eels, and on that basis ophichthids appear to have nearly the same level of endemism as all of the Hawaiian shorefishes.

Jordan and Evermann (1905) were the first to treat the Hawaiian ophichthid fauna, followed by Gosline (1951), Gosline and Brock (1960), and McCosker (1979). Since my earlier review, Callechelys lutea was photographed and collected at Johnston Island, two specimens (one each) of the widespread Indo Pacific ophichthid species Callechelys catostoma and Ophichthus bonaparti have been discovered in Hawaiian waters, and recent revisionary studies of ophichthid genera have changed the nomenclature and taxonomic status of several species. In attempting to identify the Hawaiian specimen of Ophichthus bonaparti I uncovered several synonymies of that species that were previously unreported. And finally, I have made an extensive survey of the vertebral numbers of several Hawaiian ophichthid species (including extralimital examples) and include those data in the key to assist in the identification of ophichthid leptocephali.

Materials and Methods

Measurements are straight line, made either with a 300-mm ruler with 0.5-mm gradations (for total length, trunk length, and tail length) and recorded to the nearest 0.5 mm or with a 1-m ruler with 1-mm gradations and recorded to the nearest 1 mm. All other measurements were made with dial calipers or dividers and recorded to the nearest 0.1 mm. Total length represents the tip of the snout to the tail tip; head length is measured from the snout tip to the posterodorsal margin of the gill opening; trunk length is taken from the end of the head to midanus; body length is head plus trunk length. Maximum body depth does not include the median fins. Vertebral counts (which include the hypural) were taken from radiographs. Additional vertebral data of type specimens were taken from Böhlke (1982) and from Smith (1994). Vertebral notation and definitions are described in Böhlke (1982). The mean vertebral formula is expressed as the average of predorsal...