Facelina bostoniensis or Coryphella sp.?

March 4, 2004
From: Rebecca Asch

Hi folks,
I am a graduate student at the University of Rhode Island, who is trying to identify some nudibranchs taken from dredge samples on Georges Bank. (FYI, Georges Bank is located offshore of Massachusetts, USA). According to two different marine invertebrate identification keys (Weiss, 1995; Gosner, 1971), Facelina bostoniensis is identified by the annulated rings present on its rhinopores. Species from the genus Coryphella are not supposed to have these annulated rings.

When looking through our laboratory's reference collection from Georges Bank, I found several nudibranchs identified as Coryphella sp. that had annulated rings. At first, I just figured that these specimens may have been misidentified. However, I found a picture of Coryphella verrucosa in a guide book on North Atlantic marine species (Martinez, 1994) that also looks like it has annulated rings on its rhinopores. Next, I did a Google image search and found other pictures pictures of Coryphella spp. that also appear to have annulated rings. One example of such an online photograph is the picture of Coryphella browni posted on: http://www.habitas.org.uk/marinelife/index.html

A second example is the photograph of Coryphella verrucosa posted on the following website: http://www.marinbi.com/nudibranchia/coryphella_verrucosa.htm

Are these photographs identified correctly? If so, do some species from the genus Coryphella also have annulated rings on their rhinopores?

Going back to our specimens from Georges Bank, the rhinopores are obviously annulated, but do not seem to be as long as the rhinopores shown in most pictures of Facelina bostoniensis. The samples were collected offshore at a depth of 50 m in an area characterized by gravel substrate. The particular specimen that I am examining was collected last November. However, we also have some similar looking, older specimens that were collected in past years during different seasons.

Any help with this matter would be greatly appreciated.
Thanks,
Rebecca

rasch@gso.uri.edu

Asch, R., 2004 (Mar 4) Facelina bostoniensis or Coryphella sp.?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12329

Dear Rebecca,
Firstly most workers consider the genus Coryphella to be a synonym of Flabellina so you will find more under that name than under Coryphella. We do have a key on the Forum to the Nth Atlantic species of Flabellina which you might find useful.

What I am not sure is if your are trying to identify these from living or preserved animals. If you are looking at preserved animals you may have problems even if the animals were relaxed when preserved because there is always some contraction and so smooth rhinophores, or slightly wrinkled rhinophores can appear to have distinct rings on them in preserved specimens. As you will see from the key, and the relevant Fact Sheets, some species of Flabellina do have 'wrinkles' on the rhinophores but they are indistinct and never uniform rings as in Facelina bostoniensis.

If your animals are preserved the only sure way is to have a look at the anatomy. A sure way is the radula. In Facelina bostoniensis there is a single tooth in each row while in species of Flabellina you will find the central tooth is flanked on each side by another tooth.

It's also possible that your have more than one species in your collections, of both Flabellina and Facelina
Best wishes
Bill Rudman

Rudman, W.B., 2004 (Mar 4). Comment on Facelina bostoniensis or Coryphella sp.? by Rebecca Asch. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12329

Factsheet

Facelina bostoniensis

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