Expertly Camouflaged Flatworm may Threaten Coral Reefs

A tiny and expertly camouflaged flatworm may be a harbinger of death for some coral reefs, according to a new study.

The parasitic worm Amakusaplana acroporae blends in to match the appearance of the staghorn coral Acropora, its favorite host, so well that it can barely be seen, affording it plenty of opportunity to cause damage to coral reefs.

"The biology of this worm is amazing," said Jörg Wiedenmann, a professor of biological oceanography at the University of Southampton's Coral Reef Laboratory.

Wiedenmann and his colleagues published their research on the expertly camouflaged flatworm in the journal Coral Reefs.

"By using molecular biological techniques, we found out how the worm accomplishes this excellent camouflage: When eating the coral tissue it also takes up the symbiotic alga of the coral. Instead of digesting them completely, it keeps a certain number of them alive and distributes them in its guts so that it perfectly mimics the appearance of the coral," Wiedenmann said. "Moreover, it also incorporates the green fluorescent protein pigments that lend the glowing greenish coloration to the coral host to perfect its camouflage."

Interestingly, the flatworm is well known to aquarium hobbyist who keep keep staghorn corals and fear infestation. But the flatworm has only recently been scientifically described.

"At the moment, there are no known natural predators of this parasite and only consequent quarantine can efficiently control its spread in land-based coral cultures," Wiedenmann said. "The worm is already distributed in coral cultures all over the word including regions bordering coral reefs. We do not know whether the parasite occurs naturally in these reefs and if it is controlled by natural enemies there. If this is not the case, a release of the parasite into an environment which is not adapted to its presence might have unforeseeable consequences for the regional Acropora populations."