Chromodoris dianae

Order : NUDIBRANCHIA
Suborder: EUCTENIDIACEA
Infra order : DORIDACEA
Superfamily : DORIDOIDEA
Family : Chromodorididae

One of the most common species of chromodorid observed to observe in the Philippines and Sipadan Islands, we have referred to it for years simply as Chromodoris “powder blue.” The powdery blue colour of the mantle is hard to describe because no blue pigment really exists, but in fact is created due to a fine encrustation of white over blue internal body colour. The light blue and white snow flack appearance, give the nudibranch a “Sleeping Beauty” – winter scene feeling. The gills and rhinophores are tipped in orange, and a few specimens have small patches of orange distributed along the edge of the margin. While a great deal of variation exists, there is a common theme in the discontinuous black sub marginal band and the oval black spots that occur along the midline of the notum. The sub marginal band may be nearly entire except in areas adjacent and lateral to the rhinophores or may be a series of spots and dashes. The width and shape of this band is also variable. Towards the middle of the animal, the band may occur closer to the midline. All specimens have a spot or line between the rhinophores. Posteriorly, the two black sub marginal bands may meet behind the gills or may be interrupted with a medial black spot posterior to the gills. In some specimens long oval spots form an hourglass pattern in the center of the dorsum.

Internally, characteristics of the reproductive system and radula, and well as its interesting distribution and shape of the subcutaneous mantle glands, differentiate this species from other similarly pale blue coloured species, such as Chromodoris lochi, C. willani and C. boucheti. In both, Chromodoris lochi and willani the dark dorsal lines are long and continuous, and C. willani has conspicuous white specks on the gills and rhinophores.

Known for years from the Philippines, Borneo and Indonesia, it is common in relatively shallow waters on reef walls and drop-offs, 10-30 meters deep. While not unusual to see several specimens in a single dive, we have not determined its association with a particular sponge prey, having observed it on many substrates, day and night.