The New Zealand mud snail is a small but hardy creature that can reproduce at epic rates. Dispersed across the globe on the waves of globalisation, populations of this tiny aquatic mollusc are crowding out native species in riverbeds around the world.
Now, a team of scientists from the University of Iowa, US, have deployed innovative eDNA detection techniques to identify water courses where the snail may be hiding unseen, which should allow them to identify the scale of the problem and deploy early interventions to keep populations in check beforethey do visible, irreversible damage.
eDNA refers to environmental DNA, the genetic material found in skin cells and bodily excretions that are dispersed in local water systems. A single sample of water may contain the genetic echoes of an entire community, providing a powerful window into the ecology of aquatic ecosystems. Detecting these genetic ‘fingerprints’ can enable scientists to monitor rare or threatened species and detect invaders like the mud snail.
“eDNA has been used successfully with other aquatic organisms, but this is the first time it’s been applied to detect a new invasive population of these snails, which are a destructive invasive species in fresh waters around the world,” says Maurine Neiman, associate professor in the Department of Biology and the study’s co-author.
As described in a new paper in the journal Biological Invasions, the team searched for the mud snails in eight sites across six rivers in the Susquehanna River watershed, Pennsylvania, which feeds into Chesapeake Bay and the Mid-Atlantic watershed.
Based on eDNA found in the samples, the team confirmed the presence of the snails in one site where none had previously been detected, and found there was a high chance of their presence in all other sites tested. The results confirmed their concerns that the snail had been silently colonising waterways along the Eastern Seaboard.
“eDNA can be used to find organisms at really early stages of invasion, so it can detect a population even when there are so few of the organisms that traditional methods would never find them,” says Neiman.
“This study presents an important step forward in demonstrating that eDNA can be successfully applied to detect new P. antipodarum invasions, and will allow us to more accurately track and potentially halt ongoing range expansion of this destructive invasive species,” writes the study’s corresponding author James Woodell, a research support technician at University of Hawaii at Mānoa.
The eDNA detection technique was developed less than a decade ago, and has been used successfully in all sorts of biodiversity interventions, including identifying faecal contamination in surface water, tracking invasive species like the American bull-frog, and monitoring threatened amphibians.
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