Drupella Snails 1 Drupella Snails 2 Drupella Snails 3

Drupella Snails

Drupella snails feeding on acropora

Drupella snails feeding on an acropora branching coral in Chalok Ban Kao

Drupella snails are a small mucirid gastropod found throughout the indo-pacific ocean which feeds on living coral tissue (coralivore). There is a lack of information or descriptions of these snail species prior to 1982, but subsequently they have been found in large aggregations or outbreak populations in areas such as Kenya, Australia, Hong Kong, the Red Sea, and the Gulf of Thailand.

 

These outbreaks, or overpopulations, have led to dramatic loss in living coral tissue, reduced reef resilience and recovery, population regime shifts, and possibly increased disease occurrence. The outbreaks occur due to more of the larvae and juveniles surviving, just like the case of Crown of Thorns Starfish. one female can produce over 100,000 eggs, which will turn into free-swimming larvae. Most of these larvae should not survive, they should be eaten by fish and plankton feeders (including the corals themselves!) or starve to death in the clean waters of the ocean. When the fish are removed due to over fishing, or the water quality decreases due to nutrient inputs, then more larvae survive to adulthood. Once the become adults they have very few natural predators, as they are a very unattractive food source.

 

Following the bleaching event of 2010 we experienced a large overpopulation of Drupella snails on our reefs around the Southern part of the island. Our group immediately began daily/weekly Drupella snail collections, spending over 1,700 diver hours to collect well over 10,000 snails. Additionally, we now do Drupella snail collections on most our dives, but rarely collect the data, we estimate that we have collected over 60,000 Drupella snails over the last 2 years. Recently we published a paper in the journal Coral Reefs along with Dr. Bert Hoeskema about our drupella snail findings that can be found here, or on our publications page.

 

For a long time it was thought that Drupella snails fed only on the Acropora, Pocilliopora, and Montipora corals, but in our studies we have found the Drupellas feeding on over 20 genera of corals. A study which we will be publishing in the near future.

 

Juvienelle Drupella snails size class

The range of juvenile drupella snails collected one day in 2010

But it’s not enough to only collect the snails, we are also trying to work with researchers from around the world to document the changes in populations and dietary preferences of our local Drupella Snails populations. To date, the literature has primarily focused on identifying unsustainable populations and their short and long term effects on reef health. Little or no information has been published to direct governments and other groups how to relieve or manage this problem.  We have proposed that guidelines be established and removal techniques developed to guide governments and reef managers faced with loss of economies or ecosystems values in the face of the proliferation of Drupella snails and are working to write a manual to spread the knowledge to other local reef management groups.

Drupella snails removed from Chalok Ban Kao by the NHRCP team

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