Coral Guard Crabs Defend Reefs From Corallivorous Snails

Researchers found that small crabs living on coral reefs act as bodyguards, protecting their coral hosts from harmful mucus-producing snails that can reduce coral growth by 50%. The crabs completely eliminated the negative effects of the snails on coral growth. The researchers conducted a 40-day field experiment in French Polynesia, manipulating the presence/absence of both vermetid snails and guard crabs on coral colonies to test their separate and combined effects on coral growth. Guard crabs completely eliminated the harmful effects of vermetid snails on coral growth. Without guard crabs, vermetids reduced coral growth rates by 50%. Guard crabs increased coral growth by 100% when vermetids were present. Guard crabs had no effect on coral growth when vermetids were absent. The research shows that tiny crabs may be important for coral reef resilience, especially as vermetid snail populations appear to be increasing. The findings suggest that protecting these crab-coral partnerships could help preserve important reef habitat for fish and other marine life.

Citation

Stier, A. C.; McKeon, C. S.; Osenberg, C. W.; Shima, J. S. (2010). Guard crabs alleviate deleterious effects of vermetid snails on a branching coral. Coral Reefs.

"The research shows that tiny crabs may be important for coral reef resilience, especially as vermetid snail populations appear to be increasing."

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