Mass mortality of C. maximum in French Polynesia — Update

In July 2015 we observed a mass mortality event of our focal study organism, Cereasignum (previously Dendropoma) maximum in Moorea, French Polynesia.  We have now completed surveys on other islands and have observed NO survivors on any islands in the Societies or Tuamotus: i.e., Mo’orea, Tahiti, Huahine, Raiatea, Taha’a, Bora Bora, Tikehau, Rangiroa, or Fakarava.  All that remains on these islands are old tubes that were previously occupied by live snails.  Interestingly, all other vermetid species (D. platypus, P. kenae, and S. variabilis) seem to be doing well.  We have observed healthy populations of C. maximum on Rurutu (in the Australs) and Mangareva (in Gambiers).

If you have any observations of living or dead C. maximum (from any region of the world), we would very much appreciate hearing from you.  Most helpful are data on the density (or frequency) or live snails vs. empty tubes — photographs also are very helpful.  Email any observations to  Thank you.

Vermetid nets from Hal
Typical situation with healthy vermetids extruding nets over surface of coral. Photo courtesy of Hal Lescinsky.
Situation in the midst of the die-off. Snails had stopped secreting mucus nets, had lost mass, and were deeply retracted into their tubes. Over a two week period, 90% of the snails were dead (typically mortality rates are approximately 10% per year).