UCSB Marine Biology researchers have just solved a mystery with potentially life-saving implications – why West Coast beaches are plagued with non-native mud snails and parasitic flatworms.
Led by Armand Kuris, a zoology professor in the Dept. of Ecology, Evolution and Marine Biology, researchers pinpointed the origin of Asian mud snails, Batillaria attramentaria, in the Pacific Northwest as coming from the deliveries of Pacific oyster merchants in the early 1900s. The study, recently published in the Proceedings of the National Academy of Sciences, is the first genetic analysis of an invasive marine host and its parasites, and will help scientists understand disease pathways as well as how to control disease outbreaks.
The Asian mud snails that now make a comfortable home out of the West Coast’s shores were found, through genetic research and confirmation, to be from a species native to Japan. Ryan Hechinger, a doctoral student at UCSB, said these snails came with a parasite that infects fish and birds – an example of how an invasive pest can function as a base for disease organisms.
Hechinger said the parasitic flatworm, or trematode, has decreased the native snail population in its efforts to reproduce. The parasite, Cercaria batillariae, castrates the snail, replacing its gonads with its own mass.
“The snails won’t make snail babies anymore, only parasite babies,” Hechinger said.
The parasite also negatively impacts the food chain and ecosystem biodiversity because it can harm other species such as fish and birds that become infected, Hechinger said. Researchers do not yet know the full extent of the parasite’s damage to the West Coast ecosystem.
“We’ve only looked at the tip of the iceberg,” Hechinger said. “We don’t necessarily know the negative effects [of the parasites].”
In addition, the findings of the recent study show some of the effects of increased globalization in the modern age, said Mark Torchin, a biologist with the Smithsonian Tropical Research Institute in Panama, in a UCSB press release. Along with the non-native snails, he said migratory birds brought with them another parasite, which has also been studied by the researchers.
“Genetic evidence suggests that while one cryptic parasite species experienced a bottleneck and probably came with the snails, the other was probably historically dispersed by migratory birds and could only establish in North America after the snail hosts arrived,” Torchin said. “This is because these trematode parasites have complex life cycles, using snails as first intermediate hosts, fishes as second intermediate hosts and birds as final hosts. As we homogenize biotas as a result of repeated species invasions through global trade, we increase the chances of reuniting infectious agents with suitable hosts.”
Hechinger said continued study of the parasite and its invasive host could lead to other remarkable finds: The role parasites play in the environment is large compared to their size.
“They are out of sight, but they shouldn’t be out of mind,” Hechinger said. “The parasites are extremely important components of the ecosystem.”
Hechinger said these particular parasitic populations have been studied in Bolinas, British Columbia, Ensenada, Washington and Monterey Bay. He said a population also exists in the Goleta Slough that runs north of Campus and dumps into the Goleta Pier.
“You don’t have to go all the way up there to find these cool parasites,” Hechinger said. “I love this science, the fieldwork, writing, the results, every angle. I’m going to be doing this until I die.”
Kevin Lafferty, a U.S. Geological Survey Researcher at UCSB, said he is equally excited as Hechinger about parasite research.
“[Parasites] do some of the most amazing things,” Lafferty said. “The ‘X-Files’ has nothing on the amazing things they do.”