A tiny freshwater snail measuring about four millimeters, long thought to be extinct for more than 120 years, has been discovered by accident in Tasmania’s yingina/Great Lake. Researchers surveying the Central Plateau water body found the elusive mollusc after dropping old roof tiles into the lake to attract bottom-dwelling creatures.
Freshwater ecologies often conceal surprises in plain sight. In Tasmania’s Central Highlands, a creature not recorded since the 1900s has turned up in an unexpected way, offering new clues about the health of one of Australia’s largest natural lakes.
An Accidental Discovery Using Roof Tiles
The creature in question, known scientifically as Beddomeia tumida
, was identified during conservation monitoring by Entura, a specialized arm of Hydro Tasmania. Researchers originally dropped old roof tiles sourced from a tip shop into the water, securing them with ropes and buoys between two and 10 meters deep. They hoped to catch bottom-dwelling creatures, specifically targeting another thought-to-be-extinct species: the Great Lake giant freshwater limpet.
Within ten days of placing the tiles, the survey team recovered not just the target limpet but fifteen specimens of the missing snail. Kevin Macfarlane, an Entura water quality consultant who led the survey, acknowledged the extreme difficulty of the effort. The chances of one of these crawling onto it is minuscule,
he noted.
Prior to this discovery, mollusc experts spent extensive time during the 1990s attempting to locate the species without success. The last formal records of the snail dated back more than 120 years. Andy Taylor, an environmental scientist with Hydro Tasmania, described the water body as an under-studied environment.
Following the retrieval of the specimens, zoologist Dr Karen Richards from the environment department formally identified the catch. When Macfarlane received confirmation via text message, he described the moment as really exciting
and noted that he was extremely happy
after nine years of unsuccessful searching.
Ecosystem Health and Habitat Quality
Before this recent field success, the International Union for Conservation of Nature Red List classified the snail as critically endangered but possibly extinct
.
As Beddomeia species are not present at locations of reduced water quality.
This tells us that the water quality is very good, and the habitat is very good,
Macfarlane explained.
The survival of these delicate organisms is particularly striking given the history of the lake. Great Lake is Australia’s second-largest natural lake, altered to cover 176 square kilometres after being dammed in 1901 to feed the Waddamana Power Station. Dry conditions during 2015 and 2016 caused water levels to fall to unprecedented lows, exposing the lakebed and enabling critical survey work that eventually led to the rediscovery of the limpet and, subsequently, the snail.
What Lies Ahead for the Rare Mollusc
In addition to the snail, recent monitoring efforts have uncovered other undescribed snail species, sponges, an aquatic plant, and a clover-like herb not recorded in twenty years.
