Chromodoris geometrica Risbec, 1928

Chromodoris geometrica is one of the few chromodorids in the Marshalls occasionally found crawling in the open during the day, although even these are more often found under chunks of dead coral. They can be found on lagoon reefs and pinnacles as well as on the leeward seaward reef. At Enewetak, they were most common on the sponge-encrusted pilings of the old pier at Medren Island until large swells from a southwest storm washed them and all the other pier dwelling nudibranchs away.

When crawling, this species waves its front margin up and down, almost as if it is feeling for whatever is in front of it with its front margin. There are a few other species that do the same, and curiously, many of those also have this unusual purple coloration under the front margin. On the specimen on the right, the orange patch visible under the skin behind the right rhinophore is a mass of bright orange yolk in the reproductive system. This yolk gets deposited in egg masses as orange blobs of yolk, called extra-capsular yolk bodies, adjacent to each developing ovum.

Larger specimens often have the black background around the pinkish white pustules studded with round, bright white spots.

Below is a juvenile Chromodoris geometrica (at right) along with a full-sized pink Noumea sp. e096.

Sometimes the rhinophores and gills of this species, especially of smaller specimens, are yellow instead of green.

One of the sponges eaten by Chromodoris geometrica is the purple Chelonaplysilla violacea near or under all the specimens below. In the lower one, you can see where the nudibranch has grazed some of the sponge away.

Created 14 December 2005
Updated 11 December 2008