Opisthobranch of the Week is Phyllodesmium sp.

Phyllodesmium sp.

Image courtesy of Marcel Tanke
Copyright 2011, Marcel Tanke
Wakatobi, Indonesia

Phyllodesmium sp. (undescribed)

This photo came in identified as Phyllodesmium iriomotense. After close inspection, we believe it is likely a new species of Phyllodesmium, however.

The branching digestive gland within the cerata certainly looks like Phyllodesmium iriomotense, but the latter does not have brown nodes on the gland. Also, the hydrocoral in the photo is a different species than that commonly fed upon by P. iriomotense.

This leaves us in our usual dilemma - no specimen - no more information. ID'ing opisthobranchs from photos is always very difficult and tentative. Most species display a wide variation in color, and even in shape. Just because it doesn't look like the photo in one of the fine books out there doesn't mean it isn't. Heck, Marcel's critter here could be Phyllodesmium iriomotense, who because it was feeding on a different hydrocoral, has taken on different color. Need the animal in hand to know for sure.

Dave Behrens
Gig Harbor, Washington
Feb., 2012
Send Dave email at davidwbehrens@gmail.com

Marcel and Marion Tanke at Wakatobi Resort

Marcel and Marion Tanke are working their 15th (and last) year as expat in Asia, in Shanghai at this moment. Marcel has BSAC Instructor level. Nudibranchs became their main interest after several trips to the Philippines, Anilao and Indonesia. Marion is “spotter” for the nudibranchs and Marcel takes the pictures. Marcel is still using a “point and click” camera, upgraded to Canon S95 now.
Their story on this Phyllodesmium nudibranch: While diving at about 10 meters depth at the housereef of Wakatobi Resort, our local guide Kazz (the best guide of the resort, with very sharp eyes and excellent knowledge) spotted this about 3 cm long nudibranch. Later he confirmed to have seen this type of nudibranch before, having about the same size. There are many brown- and orange- sponges on this dive site, which might explain the color of the animal.
Send Marcel email at marceltanke@cs.com

From left to right, Terry Gosliner, Angle Valdes, Dave Behrens La Jolla, Calif.

Send Dave email at davidwbehrens@gmail.com