Invading at a Snail’s Pace

Periwinkle snails, also known by their scientific name Littorina littorea, are super invaders on Atlantic coast of North America. When they are not busy being consumed by adventurous humans in a stir-fry with garlic, salt and pepper, they are competing with our local snails and disrupting the ecosystem.  Although they are still more commonly found in the shellfish section at Superstore and TnT supermarkets in Vancouver than in the intertidal zones, some of these snails have been introduced to the wild as adults. Religious organized groups and animal activists both have motives to release these snails into the wild in Vancouver. These groups may think they are setting them free from human consumption but putting them back in the wild in turn, leads to them being lunch for sea stars. This is because they have been experimentally shown to lack any sort of behaviour to prevent themselves from being eating.

But if these snails were to develop a predator avoidance response, this may cause a vertical migration shoreward. Previous studies have observed snails that are introduced to a high-predation zone from a chill, and predator-free zone would travel as much as 15 m in three  days towards the shore. Thats like a human doing this thing in this gif to travel 1.3 km for three days!!

human snail

Since the temperate rainforest are just beyond the shore in the intertidal zone, my experiment looks into whether or not these snails would be capable of surviving in the terrestrial environment. I tested lowered salinities since the snails would be exposed to predominantly rain water and what they would do when given leaves and mushrooms to eat. For each treatment group, the snails were happily placed in red solo cups.

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In each treatment, I measured whether snails were attached to something or not and then looked at how long they took to emerge from their shells and how much food they ate. At the end of the experiment, I found that many of the snails were actually so unhappy to be away from their normal food (the green algae Ulva) and normal sea water that the majority of snails died. Below is a graphic image of the many dead snails that succumbed to lower salinities and terrestrial food sources. I’m sorry, it is a bit gruesome.

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Based on my very significant results, my experiment suggests that these snails would not be able to vertically migrate all the way inland from the intertidal zone. They deeply depend on living in water with high salinity and as for now, also seem to prefer eating Ulva. With sea stars dying off from sea star wasting disease right now in our local community, the biological limitations of periwinkle establishment may gradually become reduced. Therefore, we must monitor areas with less predators as these are the places periwinkle snails would most likely establish.

What can you do to help? If you get periwinkle snails at a seafood market, don’t release them, eat them!




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