[Coral-List] Fw: Nudibranch infestation of Pavona cactus

[Sangeeta Mangubhai]

Dear Coral-listers,

Just forwarding a response I got from Mary-Jane Adams on my recent query to
coral list. It was interesting reading for me and well worth sharing. I did
find colonies covered with these acoel flatworms, but again they disappeared
with no damage observed to the corals (well at least externally).

Sangeeta Mangubhai

----- Original Message ----- 
From: "MJ Adams" <divepng at yahoo.com>
To: "Sangeeta Mangubhai" <smangubhai at africaonline.co.ke>;
<coral-list at coral.aoml.noaa.gov>
Cc: "David Obura" <dobura at africaonline.co.ke>
Sent: Thursday, May 06, 2004 9:40 PM
Subject: Nudibranch infestation of Pavona cactus


Hi Sangeeta,
Thanks for sending me the interesting image.  These slugs are
technically not nudibranchs.   They are cephalspideans, a group of
opisthobranch molluscs with a thin internal shell.  The species is
probably either Chelidonura tsurugensis, Baba 1959 or C.sandrana,
Rudman, 1973.  Reports from various parts of the Indo-Pacific show the
color pattern of both these species is quite variable and some experts
think they are synonymous.  For more information and images, see:
http://www.seaslugforum.net/cheltsur.htm
http://www.seaslugforum.net/chelsand.htm
Chelidonureans prey on acoel flatworms, the small brown patches
seen on the coral in your excellent picture.  These slugs don't have
the teeth to scrape off coral polyps; in fact they may actually benefit
it by removing the flatworms that shade the polyps.  Chelidonureans
have a short lifespans characterized by mass spawning and mass
mortality.  That probably accounts for their disappearance from your
study site.

The opisthobranch expert at the Los Angeles Museum of Natural
History,  Angel Valdes, PhD can be contacted at: avaldes at nhm.org

Best regards,
Mary Jane

=====
Mary Jane Adams
divepng at yahoo.com