OKINAWAN
OPISTHOBRANCH OF THE WEEK

Noumea angustolutea Rudman, 1990 (17mm)
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:

        Noumea angustolutea is unknown from Okinawa Island as of mid-January, 2002, 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 animal is one which was photographed in the waters of Kuba 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 July of 1997, on a rock in 12m of water. Atsushi's photograph is used here with his kind permission and he considers the species to be rare in the Kerama Islands in as much as he has seen only the above featured animal as well as a second individual which was neither measured for size nor collected(per. comm.).

        The following shape and color description of Noumea angustolutea * is taken from Rudman's original paper (1990):

Shape.
        The mantle is elongately ovate with a broad mantle overlap with some folding. There is usually a large fold on each side midway between the gills and the rhinophores. The foot extends a little behind the posterior end of the mantle when the animal is crawling.
        The rhinophore clubs are long and tapering and the rhinophore pockets are raised. The simple gills are arranged in an arc, open posteriorly, around the anal papilla. The gills have a fast flickering action. In preserved specimens there is a broad dense band of small granule-like mantle glands around the edge of the mantle. The anterior edge of the foot is wider than the rest of the foot and has angled corners.

Colour.
        The mantle is translucent creamy white with an opaque white band down the midline over the viscera, from just in front of the rhinophores to just behind the gills. The band narrows midway down the body. Around the margin of the mantle is an opaque white band with a thin orange-yellow line right at the edge. The translucent white region of the mantle skirt, between the outer opaque white band and median white band, is sometimes an opaque creamy yellow.
        The foot is translucent white, with a yellowish tinge, and there is an opaque white band right at the edge. The rhinophore stalk is transparent or translucent white. The rhinophore lamellae are a light brown to orange-red and there is a white band up the anterior and posterior midlines of the club. The gills are translucent but usually have some opaque white in the bottom half. The gill lamellae are the same brown or orange-red as the rhinophore clubs. Because the tapering of each gill reduces the white area, al the upper half of each gill appears a reddish brown.

* The name "angustolutea" comes from the Latin for a narrow orange-yellow line, having reference to the color of the mantle border, which is not discernable in Atsushi's above featured animal.

        On the Sea Slug Forum Bill Rudman (1999) features a very similar appearing animal (lower photo by Brunckhorst, from Phuket, Southern Thailand) to that of Atsushi's Keramas animal.

        Noumea angustolutea is but one of ten species currently confirmed as being found in Okinawa waters. The ten Noumea species found here to date (as of mid-January, 2002) are:

Literature Cited:


Page Date: 14 Jan '02
Page Modification Date: 14 Jan '02
Digitally manipulated photo
Copyright © 2002 Robert F. Bolland