Killer Aliens: The day the new neighbours moved in

“One Wednesday afternoon, I looked outside my tank to see new neighbours moving in next door. At first, I didn’t think anything of it. They seemed like pretty nice people, but I soon realized that they weren’t from around here. The next thing I knew, the killer alien crustaceans attacked!”

All joking aside, the introduction of nonnative species into British Columbian habitats poses a huge threat to local biodiversity! This week in Biology 326 we wanted to measure the behavioural reactions of sea snails to novel predator species.

Photo: Allison Dennert

Photo: Allison Dennert

We set out to see if the black turban snail (Chlorostoma funebralis) and the common periwinkle (Littorina littorea) had any changes in response to a threat by a native predator or a nonnative predator. The black turban snail is native to British Columbia, and the common periwinkle is native to the east coast of North America.

Photo: Allison Dennert

Photo: Allison Dennert

In our first experiment, we tested the snails’ responses to chemical cues put into the water by predators. We matched these snails with a Pacific predator (Big Dan the Dungeness crab) and an Atlantic predator (Lucky the American lobster). One would hope that these snails could develop defenses against both of these predators, but it is more likely that they are adapted to only the predators that they encounter in their natural environment. For example, imagine an alien race landing on earth tomorrow morning. It’s more than likely that we would have no viable defenses against these new invaders. Same goes for these snails!

The results of our in-class experiments were inconclusive, but we could expect that the Atlantic snails would be more scared of the Atlantic predator, Lucky, and that the Pacific snails would be more scared of the Pacific predator, Big Dan. It would definitely be interesting to follow up our experiments with more data!

Next, we tested the snails’ responses to tactile cues. That means we spent a good chunk of the class poking our snails with sea stars! We poked our Atlantic and Pacific snails with two species of Pacific sea star. We could expect that the Pacific snail, the black turban snail (Chlorostoma funebralis), would be more reactive to being poked by the sea stars. This is because the black turban snail would be used to Pacific sea star predation whereas the Atlantic snail, the common periwinkle (Littorina littorea), would not. Again, our in-class results were inconclusive in this respect and it would definitely be worth revisiting this question.

Photo: Allison Dennert

Photo: Allison Dennert

The introduction of nonnative species in BC waters is a big problem, and it is really important that we understand how this introduction affects native species so that we can better protect the world’s natural biodiversity.

Nonnative predators have become a pretty hot topic in BC media! Click on the videos below for more information about invasive species in the news.


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