OKINAWAN
OPISTHOBRANCH OF THE WEEK

Okenia liklik Gosliner, 2004 (4mm)
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:

        Okenia liklik is considered to be rare in Okinawan waters. I've not seen the animal here in the waters of Okinawa's main island and Atsushi mentions (pers. comm.) seeing and photographing only a single animal in the Keramas.* The above photograph was taken by Atsushi from the waters of Zamami Island on the 2nd of May, 2015 and he reports finding it between dead coral and stones. Atsushi's photograph is used here with his kind permission.

        The following description of external morphology and discussion are taken from Gosliner (2004):

        EXTERNAL MORPHOLOGY - The living animals are small, 3-4 mm in length. The body is elongate and relatively high. There is a well-developed, continuous notal border. Immediately ventral to the notum is a series of small subdermal mantle glands situated in the posterior half of the body The foot extends posteriorly and is devoid of notal papillae. The body color is uniformly purplish pink. There is mid-dorsal band of chocolate brown that is interrupted by connected or three interrupted, irregular opaque white markings. The gill is uniformly opaque white. All but the posterior pair of papillae are tipped with an orange subapical marking and, in some cases, a chocolate brown apex. The posterior pair and the single medial papilla are purple with chocolate brown, but lack orange pigment. There are 8-9 pairs of elongate notal papillae along the sides of the body. The two anteriormost pairs of papillae are situated in front of the rhinophores and are anteriorly directed. A single mid-dorsal papilla is present anterior to the gill. It has the form of a crenulate crest rather than a more typical digitiform papilla. The gill consists of 3 unipinnate branches. The rhinophores are elongate with 17-18 congested lamellae. The anterior end of the foot contains two elongate triangular lobes that are united medially. The genital aperture is situated on the right side of the body approximately a third of the length of the body posterior to the head. The foot is narrow and is divided anteriorly.
        DISCUSSION - Okenia liklik has a distinctive purplish pink body color with orange, brown and opaque white markings. No other described species has been described as having glands situated near the posterior margin of the mantle. As in some other species of Okenia, such as O. japonica and O. purpureolineata, the body is elongate and narrow and large oral glands are present surrounding the mouth. The relatively large, unifid outer lateral teeth are more elongate than those found in other described species.

        Rudman(2004) has an additional image of the animal initially described by Gosliner on the Sea Slug Forum and there are a series of images of Okenia liklik seen on several sites:

        There are to date the following four described species of Okenia, as well as two undescribed species known from Okinawan waters.

Etymology:

Literature Cited:


        * Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.


Page Date: 01 Jun '15
Page Modification Date: 01 Jun '15
Digitally manipulated photo
Copyright © 2015 Robert F. Bolland