[Coral-List] Massive die-off of Ceraesignum (Dendropoma) maximum in French Polynesia -- Update

[Craig W Osenberg]

Dear Coral-listers,

Over the past year, our research team (Tom Frazer, Jeff Shima, Anya Brown, Craig Osenberg) has continued to follow a mass mortality event of the vermetid gastropod, Cereasignum maximum (previously Dendropoma maximum) in French Polynesia.  In Mo’orea, over a 2 week period in mid-July 2015, we observed snails go from apparently “normal" (making mucus nets; feeding; opercula located at the edge of the shell apertures) to “lethargic” (snails greatly retracted into their shells, cessation of mucus-net-feeding) to dead (rotting in their shells).  We have now surveyed other islands in French Polynesia, and have found NO live C. maximum on any of the islands we’ve surveyed in the Societies or Tuamotus: I.e., Moorea, Tahiti, Huahine, Bora Bora, Raiatea, Taha’a, Tikehau, Rangiroa, and Fakarava.   All we have found at these sites are empty tubes that were recently (in the past ~ year) occupied by a live snail.  All other vermetid species at these sites are alive and appear to be doing well (the most common vermetids at these sites are Dendropoma platypus, Petaloconchus kenae, and Serpulorbis variabilis).

We have found healthy vermetid populations of C. maximum in Rurutu (Austral Islands) and the islands and lagoons around Mangareva (Gambier Islands).

We continue to welcome observations (i.e., notes on the frequency or density of live C.maximum vs. empty tubes and/or photographs) from other islands in French Polynesia or from other regions.   If you have the opportunity to make observations of C.max, please don’t hesitate to get in contact with us.

An initial note (Brown et al. 2016) describing the die-off is available at Coral Reefs (http://link.springer.com/article/10.1007/s00338-016-1438-8).  We are still uncertain of the cause of the die-off, but are investigating several options with the help of colleagues.

We appreciate your assistance in identifying healthy and/or extirpated populations.

Thank you,
Craig
Craig W. Osenberg
Odum School of Ecology
University of Georgia
http://osenberglab.ecology.uga.edu/
osenberg at UGA.edu<mailto:osenberg at UGA.edu>