Key found to tumors claiming Devils

They are never considered cute or cuddly, but Tasmanian devils are a cultural icon of Australia, right behind koalas and kangaroos.

Over the past decade, Tasmanian Devils of Australia have been dying off in massive numbers, felled by oral and facial tumors that prevent their eating, causing them to starve to death. In some areas, virtually all of the animals have died from the mysterious disease.

A study by researchers at Tasmania's Department of Primary Industries, Water and Environment now offers clues about how the disease is transmitted.

The study, published Thursday in the journal Nature, concludes that the animals are inadvertently transplanting tumor cells among themselves when they bite during fights and mating rituals.

The key came from an analysis of chromosomes in tumor cells, according to biologist Anne-Maree Pearse and colleagues. She found that chromosome patterns in tumor cells from the devils were identical to each other and grossly different from the devils' healthy chromosomes.

The devils normally have six pairs of chromosomes plus a pair of sex chromosomes, for a total of 14. In the tumor cells, both sex chromosomes were missing, as were both members of chromosome 2 and one member of the chromosome 6 pair. Moreover, a long section of chromosome 1 was missing and four new chromosome fragments were present.

Such a complex arrangement of chromosomes could not have occurred independently in each animal, Pearse concluded. Instead, the tumor must have originally arisen in one animal and subsequently been transferred to others when cells sloughed off during biting, allowing the tumors to take root in new animals.

Apparently, the devils' immunological profiles are sufficiently similar that the tumor cells are not rejected. One piece of evidence for this view is that devils in western Tasmania, genetically distinct from those in the east, have escaped the outbreak.

At present, the best hope for fighting the outbreak is to remove diseased animals from the wild. Studies by biologist Menna Jones of the University of Tasmania in Hobart show that when diseased animals are culled from a population cut off from other devils, the outbreak is halted.

The island of Tasmania, an Australian state, is located about 150 miles southeast of the continent across the Bass Strait.