Extinct animal was just hiding under a rock

2022-10-05

Beneath a single tree on an island 500 kilometres from Port Macquarie, an insect previously thought extinct has been uncovered—quite literally—by a biology student from Sydney University.

When Maxim Adams lifted a rock beneath a banyan tree on Lord Howe Island’s northernmost coastline, he was not expecting to find a long-missing animal.

And when he saw an intrusion of large, wingless cockroaches swarming where the rock had been, it took him a moment to realise the significance of what he was seeing.

“I lifted the first rock under this huge banyan tree, and there it was. For the first 10 seconds or so, I thought ‘No, it can’t be’,” Adams says.

‘It’ is Panesthia lata – or the Lord Howe Island wood-eating cockroach – a species thought to have been wiped out by the arrival of rats on the island in the 1910s.

Adams and his supervising professor Nathan Lo proceeded to spend a week searching for more colonies of these previously vanished arthropods, but to no avail, this was the only group found.

Still, it’s a coup, and although Lo recently wrote of the perseverance of related cockroaches on neighbouring islands, the specimens uncovered by Adams are genetically distinct.

The rediscovery and genomic analysis of P. lata further highlights how physical isolation can lead to evolutionary divergence.

“These cockroaches are almost like our very own version of Darwin’s finches, separated on little islands over thousands or millions of years developing their own unique genetics,” says chair of the Lord Howe Island board, Atticus Fleming.

“The survival is great news, as it has been more than 80 years since it was last seen. Lord Howe Island really is a spectacular place, it’s older than the Galápagos islands and is home to 1,600 native invertebrate species, half of which are found nowhere else in the world.”

What’s in a name?

There are 11 described species of the genus Panesthia, most of which reside along Australia’s east coast, feeding on rotten wood that is broken down by specialised cellulose-eating enzymes in their digestive system.

After re-discovering P. lata in July, Lo’s team will now turn its focus towards studying the species’ habitat, behaviours and genetics.

They also expect to conduct further studies on Lord Howe Island to better understand how the group found beneath the Banyan tree was able to survive.

However the researchers believe that a new name might be needed for this species, with early observations suggesting that rather than living inside rotting logs, the species may actually favour rocks like the one they were found beneath.

“We found families of them, all under this one banyan,” says Senior Scientist Nicholas Carlile from NSW’s Department of Planning and Environment.

“But despite its common name suggesting they are wood-feeding cockroaches and that they burrow in rotting logs, we now believe they are more of a ‘rock-roach’, with rocks forming an important component of their habitat, possibly due to their co-evolution alongside the ground foraging Lord Howe Island Woodhen.”

Cosmos, 5 October 2022
; https://cosmosmagazine.com