July 19, 2003
From: Alan Shepard
Here's a shot of what I believe is Okenia ascidicola from Gloucester, Massachusetts, USA. It seems to fit the description of the species as described in Bleakney's book, Sea Slugs of Atlantic Canada and the Gulf of Maine quite well. The text indicates that all previous specimens have come from the Nahant area of Massachusetts, USA.
According to Bleakney it feeds upon Molgula manhattensis, an ascidian, hence the name. When it is feeding it bores its way in to the ascidian to feed on the softer insides and only its gills project through the hole. M. manhattensis is pretty nondescript and usually covered with sand and other debris so it is often overlooked. I was very lucky to actually find O. ascidicola.
I was exploring a large boulder at a depth of about 6 meters or so when I saw some eggs that I knew I had never seen before (I do have some so-so shots of the eggs). I looked about for the nudibranch that may have layed them and saw nothing (I did notice M. manhattensis though). I swam off a bit and then spotted a 12 millimeter nudibranch hanging by a "thread" in the current (see attached). I immediately knew it was something new to me and thought it was a species of Okenia. I gently hooked the thread it was attached to with my camera's framer and brought it down to the substrate to get the other photos I've attached.
I'm hoping you or someone else can confirm my tentative identification.
Tolland, CT, USA
firstname.lastname@example.orgShepard, A., 2003 (Jul 19) Okenia ascidicola from Gloucester, Massachusetts, USA. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10075
This is an interesting find. From Patricia Morse's description I am sure you have correctly identified this rarely reported species. The habit of living in a burrow it has eaten in its prey ascidian is very reminiscent of Goniodoris meracula in southeastern Australia.