Oldest animal on earth?

Source: bangor.ac.uk
In the vicinity of Iceland a clam has been fished up from the Atlantic Ocean of whom biologists claim it to be between 405 and 410 years of age. The clam is an ocean quahog or Icelandic cyprine (Arctica Islandica). When this quahog was a youngster, the 80 year war was fought (1568-1648).
The animal was fished out and studied by slerochronologists from Bangor University of Wales during an expedition in which information about climate changes in the last millennium is collected. In order to determine the animal’s age, biologists looked at its annual rings (as is done with tree rings). This way they were able to reconstruct time periods. Especially important is the development of the water temperature in those years.

How could it be that these clams become so extremely old? The scientists of Bangor are dying to find out which mechanisms cause a slowing down of normal aging processes. This way, they hope to gain more insight in the process of aging in other beings.