Opisthobranch of the Week Data
Noumea alboannulata is considered to be very rare on Okinawa; I've personally collected only a single animal, but the above featured animal was photographed here on Okinawa by Mr. Yukinobu Adachi * and the beautiful image is taken from his Marine Photography Page, Light and Dark ( see "Slug Collection"), and is used here with his permission. In a recent personal communication, Yukinobu mentioned that he has seen other individuals (also at Maeda-misaki) between a depth of 3 & 30 meters, usually during Okinawa's winter months. The featured animal was found and photographed at the reef edge, during a mid-morning dive, on rock.
In Rudman's original description of the species (1986) he points out the following:
In external coloration Noumea alboannulata is most similar to Chromodoris decora but the internal anatomy clearly shows that they are distinct. The anatomy of this species places it in the genus Noumea . . . . It differs from most species of Noumea in having rhythmically moving gills, . . . which is more characteristic of Thorunna and Glossodoris.
The animal was named 'alboannulata' due to the white ring, which is somewhat constricted anteriorly on the upper mantle surface. See Bill Rudman's Slug Forum for several images of N. alboannulata, which show some of the color variation seen within the species . . . one of the "Forum Animals" is very similar to the above featured animal.
N. alboannulata is known from widely separated parts of the tropical Indo-West Pacific, the Red Sea, and the Coral Sea (Rudman, 1986).
My experience with the other six described species of Okinawan Noumea is that none are apt to be confused with N. alboannulata; as it turns out, the bright white median band which divides posterior to the rhinophores, forming a pair of white longitudinal lines which surround the gills, make this a very unique appearing chromodorid.
* Background Information on Mr. Yukinobu Adachi: