OKINAWAN
OPISTHOBRANCH OF THE WEEK

Jorunna rubescens (Bergh, 1876) 155mm

Opisthobranch of the Week Data

Taxonomy:

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


Species Account:

        Jorunna rubescens was previously featured on the Okinawa Slug Site (27th of January, 1997) as Kentrodoris rubescens. In a recent paper by Valdés & Gosliner (2001) the authors regard the genera Kentrodoris and Jorunna as synonyms and have selected the name Jorunna to have precedence over Kentrodoris. In as much as it's time to update the much earlier page, I've decided to following the Valdés & Gosliner paper in using J. rubescens. The following description of external morphology is taken from Valdés & Gosliner (2001):

External morphology

        The maximum length of this species reaches 170 mm (Willan & Coleman, 1984). The body is elongate, narrow and very elevated. The texture is soft and velvety. The dorsum is entirely covered with long caryophyllidia*, about 130 µm in length. They have a long, conical base, long spicules and a small, elongate ciliated tubercle. The rhinophoral and branchial sheaths are very elevated and regular. There are seven short, bipinnate branchial leaves, forming a circle, posteriorly closed by the anal papilla. The rhinophores are elongate, with 25 lamellae in a 38 mm preserved length specimen.

        The general colour of the living animals varies from cream to pale orange. Normally, the anterior and posterior edges of the notum, as well as the edges of the rhinophoral and branchial sheaths, are darker, sometimes almost black. The entire dorsum is covered with numerous longitudinal dark brown streaks. Among them, there are several orange low protuberances, which are also present in the rhinophoral and branchial sheaths. Near the edge of the mantle there are several broken, longitudinal white lines. The rhinophores are dark brown with the apex white. The branchial leaves, have the same colour as the dorsum, except for the rachis, which is white proximally and dark brown distally. The rachis of the secondary and tertiary branches is also dark brown. The rhinophores may have dark brown spots near the apex.

        Ventrally the anterior border of the foot is notched and grooved (Fig. 17F). The oral tentacles are conical. The mantle margin is wide, but stays close to the laterals of the foot. The foot has the same colour as the dorsum, with an irregular pattern of broken brown streaks. The laterals of the foot have a pattern of white lines and some short brown streaks.


*See the Caryophyllidia page for a description of these small spiculate structures

        Jorunna rubescens is considered to be rare on Okinawa's main island. Five specimens have been collected, although perhaps 2-3 others have been seen. Three of the five collected animals were found at the Manza site which is primarily a shallow sandy lagoon with large populations of miscellaneous octocorals (Lobophytum, Sarcophytum, and Sinularia species). The five collected specimens, as well as the non-collected individuals, were found crawling on the surface of open sand during the day. This unusual-appearing dorid always reminds me of the face of a doleful little puppy, waiting for someone to pick it up. I've included a second page with several additional images of the above featured animal and other collected specimens.

Literature Cited:


Page Date: 02 Dec '02
Page Modification Date: 16 Jul '12
Digitally manipulated photo
Copyright © 2012 Robert F. Bolland