Dangerous snails

Nassarius papillosus

Nassa mud snails (genus Nassarius) are small sea snails that are very active scavengers, feeding on crabs and carrion such as dead fish. They often burrow into marine substrates and then wait with only their siphon protruding, until they smell nearby food. As scavengers, they help maintaining the ecological balance of their benthic community.

They are also useful for biomonitoring of Tributyltin (TBT) in marine environments. Due to a high specificity and sensitivity to TBT, imposex is found in some Nassarius species. Imposex is a toxin-caused pathological condition were snails develop sex organs that are in contrast to their actual sex. Imposex levels are considered the best biological indicator of TBT pollution in aquatic environments.

Even more importantly, there is a serious food safety problem involving these snails. There is a range of species occurring at China's coasts and most local Nassarius species are consumed as food. Due to the life style of the snail, a variety of toxins (e.g. tetrodotoxin) can be accumulated in their body and pose a threat to consumers. In the last couple of years several food poisoning incidents caused by Nassarius have been reported in China. In some cases victims died of the poisoning. This led to a regional ban that prohibits the sale and consumption of Nassarius.

Recent studies showed that the toxicity of Nassarius is species specific. For example, N. hepaticus is considered toxic while N. festiva isn't. In another species (N. succinctus) the toxicity changes seasonally.

A group of researchers from the Ocean University of China, Qingdao have now tested the utility of DNA Barcoding to help with species identification as it is not as straightforward as needed for food safety monitoring. Their results are very promising as they were able to show that DNA Barcoding is capable to distinguish between species. Furthermore, they found several cryptic species candidates and more concerning high levels of phenotypic plasticity in one species.