Tidy towns

Dr Ivan Marin collecting shrimp.
Image: Gary Cranitch.


4 September 2010
The family of shrimp studied by Dr Ivan Marin may be the clean freaks of the marine world.
Dr Marin, a scientific researcher at the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, is looking for shrimp of the family Palaemonidae on the CReefs expedition to Lizard Island this month.
The Palaemonidae are divided into two subfamilies: Palaemoninae are usually found in freshwater environments, while Pontoniinae are usually found in marine habitats such as coral reefs.
Shy, delicate, only half a centimetre long, and mainly transparent or cryptic coloured, pontonines are not easy to find, and until recently, little research has been devoted to them. Dr Marin's work, however, has found that pontonines play an important role in coral reefs.
"They clean coral reefs. They extract hard pieces such as stones, sand particles, or sediment from the body of the coral or from the sponges, wherever they are living, and move the detritus away from their hosts," Dr Marin explains.
Almost all pontonines establish symbiotic relationships with larger marine invertebrates including sponges, molluscs, cnidarians, such as corals, anemones and jellyfish, and echinoderms, such as sea stars, sea urchins and sea cucumbers. Different Pontoniinae species have preferences for different hosts; for example Coralliocaris live on hard corals of the genus Acropora while Anchistioides always live inside sponges.
"These relationships are of a kind called mutualism, in which both animals benefit. The shrimp live inside a coral, for instance: the coral protects the shrimp and the shrimp clean the coral," Dr Marin explains.
The shrimp may also eat mucus produced by corals and eat scraps of food left from the meals of their hosts.
"The shrimp play a very important role. There have been experiments by others scientists who have removed the worms, shrimp, crabs and other tiny crustaceans from colonies of coral. The coral died because it couldn't clean itself," Dr Marin says.
Research into the role of symbiotic relationships in coral reefs may have significant implications for conservation.
"Scientists have tried to understand, for example, what causes coral bleaching, which may be related to warm or cold waters in coral reefs. Maybe changes in water temperature killed the symbiotic assemblage, and the coral died because the symbiotic relationships were destroyed," he says.