I found my true calling; coaxing hermit crabs out of their shells (in the name of science of course).

This week our class’s lab was the perfect example of how a seemingly serious (and important) topic in science, can quickly become a platform for what I call “scientific tom foolery”, given the right people and the right study animal. Of course, what do you expect when you give a class of marine invertebrate nerds to chance to play with hermit crabs….

Our lab started out strong and serious, as we began with a lecture on how climate change. As carbon dioxide (and other green house gases) increases in our atmosphere, sea water will consequently change too and expose marine life to new living conditions. We discussed the widely distributed and sever coral “bleaching” events, where corals under high temperature, lose their ability to harvest light energy, leaving only their white (bleached) skeletons. When scientists first started studying how marine invertebrates may respond to climate change, the main environmental condition they were investigating was temperature. However, now researchers investigate how multiple environmental conditions work together and invoke a stress response in marine invertebrates (multiple stressors). For example, how do invertebrates deal with raised temperature, lowered salinity, and a combination of the two?

We decided to run our own “multiple stressors” experiment on the charismatic marine invertebrate, the hermit crab (pictured below). Instead of spending energy on growing their own shell, hermit crabs are “naked”, but steal empty snail shells and tuck their backsides into them for protection.  We chose to see how hermit crabs respond under temperature and salinity stress, and whether one stressor has a larger effect than the other. We expose these crabs to tanks of high salinity + low temperature (our control treatment) and compared them to crabs in tanks of high salinity or high temperature, and a tank with both high temperature and low salintiy (the multiple stressor treatment).

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A typical sized hermit crab of the species Pagurus hirsutiusculus in its borrowed shell.  Photo  credit: wikimedia.org

We needed a behaviour to compare between our treatment tanks, and one of the responses we measured was how long it took the crabs to find their shell after being removed from it. Now this is where the “scientific tom foolery” comes in to play, as the serious side of science teams up with the goofy side of experimenting on invertebrates.

We started by holding the crab upside down by its shell. This worked for some crabs but for more stubborn crabs, we had to get creative. Eventually we started shaking the crabs out of their shells (the crabs might have not been too keen on that, but that’s why it worked!). For some we had to hold them out of the water, with their claws just touching the water surface, coaxing the crabs to leave their shells willingly. One crab had a longer shell and was not willing to part with its prized possession. I tried my proficient techniques but this one required some thing bigger and better. This is where Doctor Harley had to step in with his decade long skill set of mastering the hermit crab removal. With the combination of heat stress via a table lamp, and a couple pokes, but we finally got the sucker out (pictures below)! Turns out it takes more than just a bachelor degree to master the hermit crab removal.

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Our tricky hermit crab after we finally pull it from its prized shell. 

For more information of coral bleaching and multiple stressor studies, check out the work being done at The ARC Center: https://www.coralcoe.org.au/

and give this article a read for further information: http://www.academia.edu/4869207/Evidence_for_multiple_stressor_interactions_and_effects_on_coral_reefs

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