Snail of destruction

A little-known marine snail may be destroying coral reefs at an alarming rate, scientists report this week in the Royal Society journal Biology Letters.  The creature, described as a “zoological oddity” by the authors of the study, is known as Dendropoma maximum and belongs to a bizarre family of snails which fix themselves to a hard surface (such as coral) and catch their food using a ‘mucus net’.  Although previous work has pointed towards the organism’s harmful effect on certain coral species, this is the first time that the snail’s effects on multiple species of corals have been described, raising concerns that the creature may be a significant factor in worldwide coral decline.

The researchers, based at the Victoria University of Wellington and University of Florida, studied the effects of the snails both in the wild and in artificial experimental environments.  They found that in the wild, the snails tended to be found near dead coral more often than living coral.  The snail’s harmful effects on the coral were confirmed when the coral was transferred to the lab and the effects of vermetid presence studied systematically – the snails reduced skeletal growth of corals by more than 50% and reduced colony survival by up to 40%.  The authors speculate that the snail’s mucus net may be the cause of the destruction, although this is as yet unclear.

While the research was based on corals found in seas surrounding French Polynesia, previous work suggests that the destructive snails may also be at work near the Pacific island of Guam and in the Red Sea.  Very little is known about the vermetids, leading the authors to suggest that their destructive effects on coral may be much more widespread than the limited geographical area in which they have been studied up to now.

At a time when corals are under threat from many different quarters, it seems that significantly more research into these strange creatures must be undertaken.  As the authors point out, “vermetid gastropods, though poorly studied, have the potential to greatly influence corals and possibly induce cascading effects on associated fish and invertebrate communities...Unfortunately, vermetids are a zoological ‘oddity’ and remain understudied”.