OKINAWAN
OPISTHOBRANCH OF THE WEEK

Berghia chaka Gosliner, 1985 (ca. 14mm)
Photo by Jun Imamoto

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 above featured animal, Berghia chaka, was photographed by Jun Imamoto in the waters of Gahi Island in the Kerama Islands, 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 found by Jun during March of 2002 in 9m of water from an area of dead coral. I've added a second image of the same animal as above. Both images of this uncommon aeolid are used here with the kind permission of Jun. I've not personally seen B. chaka in the waters of Okinawa's main island and Jun reports (per. comm.) seeing only the single above featured individual. More recently I've added two additional pages of B. chaka showing images of two separate animals collected by Atsushi Ono, also from the Kerama Islands.

        B. chaka was described by Gosliner (1985) based on specimens from Jesser Point, Sodwana Bay National Park, Natal, southern Africa. The following description of external morphology and coloration are taken from Gosliner (1985):

External morphology
        The living animals reach 10 mm in length. The oral tentacles are slender and tapered. The rhinophores are approximately equal to the oral tentacles in length and possess scattered, elongate papillae. The foot is moderately broad. Anteriorly it is deeply incised and slightly more posteriorly a transverse groove is present. The anterior end of the foot is broad and rounded, without angular or tentacular extensions. The cerata are irregularly shaped with a few tubercles along their lengths. The anterior right digestive branch consists of a single arch of eight cerata. The first branch of the right posterior digestive system is also an arch composed of ten cerata. The two to three branches posterior to this may consist of partial arches or linear rows of two to six cerata. The gonopores are situated ventral to the first ceratal arch while the anus is located within the second arch. The nephroproct is immediately anterior to the second ceratal arch.

Coloration
        The living animals were translucent white covered with a dense pattern of opaque white pigment over much of the body. The head and basal halves of the rhinophores and oral tentacles are covered with chocolate brown pigment. Brown is also present at the bases of the cerata and more diffusely on the dorsal portion of the foot. The digestive gland within the cerata is rusty brown. The cerata are ornamented with opaque white pigment, which is most dense on their anterior side and on the irregular tubercles. The tips of the cerata are opaque white. A thin subapical band of chocolate brown is present, as is a wider band of opaque white.

Etymology:

Literature Cited:


Page Date: 02 Feb '04
Page Modification Date: 15 Oct '07
Digitally manipulated photo (image has been horizontally flipped)
Copyright © 2007 Robert F. Bolland