A Galapagos chromodorid, deep blue with yellow lines and a pale margin, on sponge under ledges.
Sources give anything from 3.8 to 10 cm, and the larger figure is poorly supported; treat it as a small nudibranch of a few centimetres. Dark brown to reddish-brown or nearly black, covered in round yellow spots, and some animals also carry larger blue spots. The mantle margin is an interrupted band of yellow and pale blue. The rhinophores are black and the gills are cream or translucent gold with darkened tips.
Several other eastern Pacific species of the same genus are the confusion. The round yellow spots on a dark ground, with black rhinophores, separate this one; the commonest of the others is blue with yellow lines running lengthways rather than spots.
It eats sponges — at least nine species of them have been identified from gut and faecal analysis — and is found on rocky reef in daylight, in shallow water. No reliable maximum depth has been published. It is native to the Galapagos and occurs from the Gulf of Panama north to Mexico. It is named for Alexander Agassiz, whose dredging expedition first collected it.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
