UC student aims to stop snail invasion

Sarina Talip

2 June 2014: It's no bigger than a grain of rice, but the New Zealand mud snail is invading our shores according to University of Canberra PhD student Adrian Dusting, who is trying to find out how they’re doing it so he can help stop these tiny, slimy invaders.

Mr Dusting said the four millimetre mud snail, or Potamopyrgus antipodarum, has “invaded freshwater rivers, streams and lakes in south-eastern Australia, assailing important but sensitive native bug life such as endemic snails and mayflies, outcompeting them for space and food and driving their local extinction.”

He said no one really knows how the New Zealand mud snail ended up in Australia in the first place with specimens dating back as far as 1872, and that the miniscule mollusc has also invaded waterways in the United States, Asia and Europe.

Adrian Dusting gets up close to the tiny New Zealand mud snail. Photo: Michelle McAulay

What’s amazed Mr Dusting is that it has not only succeeded where other species have failed, it has thrived. This is particularly surprising because the invasive snails are asexual, and asexual species are less effective at adapting to their new environments than sexual species.

“Sexual species generate genetic diversity through sexual recombination – when a female and a male get together, positive and beneficial adaptive traits come up more often and are passed on to their young,” he said.
“But that doesn’t happen as often in asexual species. Asexual species pass on the whole genome of the mother to the daughter, so adaptation can therefore only occur very, very slowly through mutation, rather than through sexual recombination.

“Because adaptation occurs so slowly in asexual species, you would imagine that this potentially compromises the snail’s ability to adapt - and yet we find New Zealand mud snails everywhere across a wide range of environments and countries.

Mr Dusting hopes to uncover the specific characteristics that make the mud snail a successful invader when others have failed. He said this may be partly explained by the fact the females are extraordinarily fertile, with each female capable of producing 240 young a year.

It is also resistant to digestion and desiccation, with the ability to survive days without water and hide safely in its shell if eaten by a fish until it’s passed out the other end, thanks to its “really funky” physical feature called an operculum, like “a trap door on its shell”.

Part of Mr Dusting’s research is establishing whether there is one genotype of the mud snail, meaning many generalists from the one clonal family flung far and wide across different environments, or lots of genotypes – local specialists that have adapted successfully to their local environments.

“I’m in the early stages of establishing this now, but using genetic techniques I’ve worked out that we do indeed have multiple clonal families,” Mr Dusting said. “We’re now trying to figure out if this is due to local adaptation or not.”

His research is a mix of fieldwork, laboratory work and experimental work. In his lab at the University he keeps thousands of snails he has collected on field trips in Victoria and New Zealand. Mr Dusting is also building family trees and establishing relatedness between the mud snails he has captured, which will help him to infer whether Australia has had multiple introductions of the snail.

Read more about Mr Dusting’s research in the latest Monitor magazine.