Surprisingly, parasites that once fed on the extinct Tasmanian tiger, also known as the Thylacine, still exist today.
One such parasite, a species of flea, has managed to survive, although the last known Tasmanian tiger died in 1936.
Thylacines were native to mainland Australia and the islands of Tasmania and New Guinea. The iconic species first appeared about 4 million years ago and was the largest living carnivorous marsupial before disappearing, driven in part by human persecution.
While the last known thylacine died in a zoo in Tasmania in 1936, the International Union for Conservation of Nature didn’t declare the species extinct until 1982.
At the time, international standards dictated that 50 years had to pass without confirmed records of an animal before it could officially be declared extinct.
Given that scientists know relatively little about the thylacine itself, knowledge about its parasites is surprisingly robust.
“Fortunately, the last thylacine died relatively recently, in 1936, and over the century or so before that, support for science and natural history in Australia grew steadily. That meant there were scientists and museum curators collecting specimens, including thylacines and their parasites,” said Mackenzie Kwak, a parasitologist at the University of Hokkaido in Japan news week.
“Many of these specimens are still protected in museums today, giving researchers like me the opportunity to learn more about them and share this information with the public and other scientists.”
Kwak, who was born and raised in Australia, said he “got hooked” on parasitology in his final year of his bachelor’s degree and has been researching parasites ever since.
“I think almost every Australian – myself included – has an innate fascination with the Thylacine, not just because it’s an Australian icon, but also because it was such a large and spectacular animal.”
Three species of parasites have been identified from Thylacine: the flea mentioned above, a roundworm and a tapeworm.
“Interestingly, roundworm and tapeworm were accidental infections, with the roundworms coming from an unfortunate pigeon that was caught and eaten by a thylacine at London Zoo, and the tapeworm likely infected by a thylacine eating a Tasmanian devil’s droppings,” said kwak.
“However, the thylacine likely had many other parasites, if their relatives the quolls and Tasmanian devils are any indication. Unfortunately, any chance of understanding these other mysterious parasites probably disappeared when the thylacine became extinct,” he said.
According to Kwak, the Tasmanian tiger parasites probably didn’t inflict too much damage on their host.
“In most cases, we find that parasites that have co-evolved with their hosts over a long period of time typically settle into a fairly amicable existence with their host,” he said. “We are also increasingly realizing that parasites can actually help train the host’s immune system, which may help reduce the risk of allergies and autoimmune diseases. So parasites may have even benefited Thylacine in their own little way.”
The burrowing flea (Uropsylla tasmanica) is the only natural thylacine parasite that still exists today. It survives in Australia on quolls and Tasmanian devils – two other species of carnivorous marsupials.
Kwak said it’s surprising that this flea still exists, as it specializes in living on the thylacine.
“When a species goes extinct, very often its host-specific parasites also go extinct – a process we call the extinction cascade. So it’s remarkable that the burrowing flea is alive and well today, especially considering that the quolls and Tasmanian devils on which it survives are actually quite distantly related to the thylacine and belong to a very different family of marsupials “, he said.
“The flea seems to have hedged its bets by parasitizing a range of carnivorous marsupials – a quirk of its ecology, but a very fortunate quirk nonetheless!”
According to Kwak, the burrowing flea had a “very unique” relationship with the Thylacine.
“Unlike other fleas, burrowing flea larvae are also parasitic and embed themselves in the host’s skin, although the adults closely resemble the typical fleas that most people know and loathe,” he said. “They would have lived in the thylacine’s fur and taken small blood meals from their host.”
Nearly a century after the death of the last known thylacine, some scientists have begun working to “eradicate” the species. If these efforts, which use advanced gene-editing technology, prove successful, it will have a significant impact on the grave flea.
“If the thylacine were to be revived through extinction research, sooner or later conservationists would push for it to be reintroduced to Tasmania so that it can once again perform its ecological functions,” Kwak said.
“Given that the burrowing flea and its remaining hosts are already widespread in Tasmania, it would really only be a matter of time before the fleas ‘naturalize’ back onto the Thylacine. Maybe by 2040 Tasmania will have the burrowing fleas and Thylacine back together in the ecosystem like it did 200 years ago in 1840!”