OKINAWAN
OPISTHOBRANCH OF THE WEEK

Flabellina exoptata Gosliner & Willan, 1991 (25mm)
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:

        The holotype* of Flabellina exoptata was collected from Papua New Guinea on 19 January, 1988 and this highly attractive flabellinid was named exoptata by Gosliner & Willan (1991) in reference to the strikingly beautiful color of the species; the species name means "much desired".

        The following description is taken, in part, from the description of external morphology by Gosliner & Willan (1991):

        The living animals reach 30mm in length. The general body color is deep pinkish purple. Basally, the oral tentacles are the same color as the rest of the body. Their middle third is deep purple and the outer third is generally opaque cream yellow. Purple pigment is also present on the apical portion of the foot corners. The rhinophores are vivid orange with yellow pigment on the apices of the rhinophoral papillae. The basal half to two-thirds of the cerata is pinkish purple. Above this section, a deep purple ring is present. The apical portion of the cerata is opaque cream yellow.

        The body is stockier than other members of the genus . . . . The rhinophores are thick basally, and terminate in a distinctly pointed apex. The posterior side of each rhinophore bears over 120 densely packed, elongate papillae. The foot corners are elongate and tentacular, and are generally recurved posteriorly when the animal is actively crawling. The cerata are thick and cylindrical for most of their length, but taper to an acute apex. The cerata are slightly elevated from the notum on a common peduncle. The cerata are arranged in distinct rows.

        Bill Rudman has a terrific close-up photograph posted on the Sea Slug Forum of the bright orange papillate rhinophores of F. exoptata, which are characteristic of the species. The animal is reported to feed on the athecate hydroids Halocordyle disticha (Marshall & Willan, 1999) and Eudendrium sp. (Gosliner, et al, 1996).

        I've not personally seen nor collected any specimens and it is unknown from Okinawa Island at the current time (late August, 2001), but it has been photographed by Atsushi Ono in the Kerama Islands. 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 animal is one which was photographed from a small bay in the waters of Zamami 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 from a small bay in 3m of water and the subject was found on the side of a cliff. The date of the photograph was not recorded. Atsushi's photograph is used here with his kind permission and the species is considered to be uncommon in the Kerama Islands (Ono, via per. comm., mentions seeing more than ten individuals).

        Flabellina exoptata is widely distributed in the Indo-Pacific (Gosliner & Willan. 1991) and it is one of six described Flabellina species presented on these pages. These six species known from Okinawan waters are:

  • F. bicolor
  • F. delicata
  • F. exoptata - the above featured animal
  • F. macassarana
  • F. riwo
  • F. rubrolineata
  •         *Holotype: See "Type" Dictionary for explanation.

    Literature Cited:


    Page Date: 27 Aug '01
    Page Modification Date: 01 Sep '13
    Digitally manipulated photo
    Copyright © 2013 Robert F. Bolland