Opisthobranch of the Week Data
Noumea norba is considered to be uncommon on Okinawa; ten specimens have been collected here since the first was found in May of 1987, but others have been seen, but neither photographed nor collected. The above featured animal was collected from 41m on a vertical wall at the reef edge covered with miscellaneous encrusting and free standing populations of bryozoa, cnidaria, porifera, and others.
On Okinawa this relatively small but very attractive dorid most closely resembles both Noumea varians and Noumea purpurea in color. In an earlier publication, Rudman (1986) considered Noumea norba to be a synonym of N. purpurea, but more recent information involving the anatomy and color variations of the species suggests the two species are indeed distinct. The following is taken from Rudman (1999):
In Noumea norba the background colour of the mantle can vary from reddish purple to pinkish orange in different specimens. There is a broad milky yellow or creamy white band around the mantle edge and on the inside edge of this band are a series of reddish purple streaks or smudged marks. In the midline there is a broad band of irregular width of the same colour as the mantle border. This band always encircle the gill pocket and can be broken in two about half way along its length. The gills and rhinophores are tinged with orange-red. Noumea norba and Noumea varians are quite similar in colour however their internal anatomy is quite different. One way of distinguishing living animals is that N. norba is quite like a species of Chromodoris in shape with a relatively wide flattened body and broad mantle skirt while N. varians is more like a Hypselodoris with a relatively high body and narrow mantle skirt.