The Great Barrier Reef off the coast of Australia has been in decline
for some time. A disease called white syndrome is killing the coral and
causing the coral tissues to slough off, leaving the coral skeleton
bleached 
Furry Coral Crab (You Tube Image)white. Now the furry coral crab, once thought to be one of the
culprits behind the death of the reef, has been discovered to be helping
slow the spread of the disease.
The cause of the disease is still unknown, although it is thought that warmer water temperatures are considered to be a contributing factor. Coral that has taken decades to form can be destroyed by the disease in a few months. Increased coastal run-off, more marine traffic, and additional coastal development may also be factors in the decline of the reef. Predation by the crown-of-thorns starfish has also been causing heavy damage to the reef.
Crown of Thorns Starfish (Photo by Jon Hanson/Creative Commons via Wikimedia)The small crab appears to be covered with fur and has large blue eyes on stalks. It grows to be about a half an inch large. Research has shown that they are attracted to coral suffering from white syndrome and will migrate away from healthy coral to get to the infected coral. Once they arrive they slow the spread of the disease by a significant amount.
It is uncertain what it is that the crabs are doing to help the coral, but it is hoped that their assistance will help the coral survive to put up its own immune defense, or for the water temperatures to fall.
Source: Terra Daily, Wikipedia
