Trepezia flavopunctata. The largest species of guard crab.
Photo: Seabird McKeon
A stunning example of mutualism - the sort of cooperation which 'selfish gene' theory predicts - was published recently by Smithsonian.com - the online science magazine of the Smithsonian Insitute.
It shows how a complex ecosystem like a coral reef has evolved a defensive system of guard crabs which receive shelter in crevices in the coral and nutrients in return for vigorously defending the living coral polyps from attack by predatory molluscs and starfish. Its not just the presence of the crabs themselves which is important but the presence of several different types, each with a particular role.
While the relationship between coral and crab has been known for a while, researchers have now found