OKINAWAN
OPISTHOBRANCH OF THE WEEK

Hallaxa hileenae Gosliner & Johnson, 1994 (13mm)
[photo by Atsushi Ono]

Opisthobranch of the Week Data

Taxonomy:

Frequency on Okinawa:
Collection Data:
[brackets indicate range for all Okinawa-collected specimens of the species]


Species Account:

        Hallaxa hileenae is unknown from Okinawa Island as of early April, 2001, but the close proximity of the main island of Okinawa to the Kerama Islands, as well as the similar opisthofauna to that of the Kerama Islands, suggests the possibility that it is also present here on Okinawa proper. The above featured, but uncollected animal, is one which was photographed in the waters of Gahi Island, one of a series of islands in the Kerama Islands Group, which are located 30 ~ 40 kilometers west of the Okinawa capitol, Naha. This featured animal was photographed by Atsushi Ono during September of 2000 in the South area of Gahi Island in 14m of water from the surface of a rock on the reef. Atsushi's photograph is used here with his kind permission. It should be noted that Atsushi considers the species to be rare in the Kerama Islands as he has seen only four individuals (per. comm.). In addition to the 13mm animal above, Atsushi also has an image of a 4mm juvenile on Bill Rudman's Sea Slug Forum.

        Gosliner & Johnson (1994) point out that H. hileenae is immediately distinguishable from other members of the genus by its purple color with black maculations and the distinct y-shaped ridge present on the notum. Of the four described species of Okinawan Hallaxa, H. indecora is the most similar in appearance to that of H. hileenae. However, the black maculations and the distinctive y-shaped notal ridge of H. hileenae (neither of these two characteristics are found in H. indecora) serve to immediately separate the two species.

        The species name was chosen by Gosliner & Johnson in honor of Eileen Sobeck, who assisted in the field work in Papua New Guinea (Hileen is the Papua New Guinea pidgin name for Eileen).

        Hallaxa hileenae is one of five species currently known from Okinawan waters (as of early August, 2004); the five species are:

  • H. cryptica
  • Hallaxa hileenae - the above featured animal
  • H. indecora
  • H. iju
  • H. paulinae
  • Literature Cited:


    Page Date: 09 Apr '01
    Page Modification Date: 09 Aug '04
    Digitally manipulated photo
    Copyright © 2004 Robert F. Bolland