Lobsters and crabs and sea stars… oh my!

This week in the BIOL 326 lab we stayed inside and explored how snails react when they come into contact with different kinds of predators. In truth, we terrorized snails with lobsters, crabs, and two different kinds of sea stars in order to see which they were most afraid of. The results of what we did are actually really interesting and important because how snails react to predators can say a lot about which predators have the strongest influence on snail ecology and distribution.

Chlorostoma funebralis

Littorina littorea

We started off by using two different kinds of snail, one called Littorina and another called Chlorostoma. Chlorostoma is a species that is native to the waters around British Columbia while Littorina is a species from the Atlantic that was only recently introduced to British Columbia (presumably by accident). We were interested in whether the introduced and native snails would be more or less afraid of predators normally found around Vancouver as compared to introduced predator species. For this we employed the services of Lucky the Atlantic lobster and Big Dan the Dungeness crab (whose name did not disappoint in case you were wondering). We put each of the two species of snail into three different bottles of seawater: one that smelled of lobster, one that smelled of crab, and one that did not smell of anything. We then timed how long it took for each snail species to panic and clamber up out of the water to safety. We expected that Chlorostoma would be most frightened by the smell of crab because it is also a BC native and that Littorina would be more afraid of the scent of lobster. However, we found that Chlorostoma did not react any differently to either of the predators and that Littorina was actually more afraid of the smell of crab. This was contrary to our expectations in both cases.

Pisaster ochraceus

Evasteria troschelii

In our second experiment we wanted to know whether the snails also responded differently when they were touched by different predators rather than if they smelled them. For this we used two species of predatory sea stars: Pisaster and Evasterias. We placed both kinds of snail in a tank with clean seawater without the scent of any predator and then performed three trials on each snail species. In the first trial they were poked in the face with a Pisaster arm, in the second they got a taste of the Evasterias arm, and in the third they received a jab from the end of a thermometer. We then measured their response by recording whether they turned or not and by seeing how fast they fled from the sight where they were poked. However, like the previous predator experiment, we found that the snails reacted the same way to both predators.

For more information about the predator responses in snails check out these links below:

http://www.academia.edu/4399663/Freshwater_snails_alter_habitat_use_in_response_to_predation

http://link.springer.com/article/10.1007/s004420050724

If you want to see a dramatic example of a snail escape response have a look at the slowed down footage of a Gibberulus snail here:

https://www.youtube.com/watch?v=kurUSuU13SkChlorostoma

All photos obtained from google image.