Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.
Assassin snail (Anentome helena), also commonly known as Clea helena, is a small freshwater predatory snail that feeds on live and decaying prey. In Thailand, Clea helena is a carrier of Angiostrongylus cantonensis, a rodent nematode that can infect humans. A. helena is widely available in North America, Europe and Asia via the aquarium trade. Much of what is currently known about A. helena is limited to aquarium observations, indicating a need for more research of the species in its natural habitat. It has been introduced to a reservoir in Singapore, where it has become established, but there are no studies of its impacts available. However, multiple authors have expressed concern about potential impacts to native snails based on the predatory nature of A. helena. Given the absence of scientifically credible studies of impacts where A. helena is established, history of invasiveness is classified as “None Documented” and the certainty of assessment is low. The climate match for A. helena with the contiguous United States is low, with areas of medium match in south Florida and south Texas. Given all factors, the overall risk assessment for Anentome helena is uncertain.
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Uncertain Risk
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