Climate Change and the Hairy Hermit Crab

This week, we had the pleasure of playing with hairy hermit crabs, and testing how decreased salinity and increased temperatures in the ocean will affect them. These two factors are interesting when we consider climate change. Temperatures are on the rise globally, and as a result, glaciers are melting and increasing the amount of snowmelt entering our oceans. This causes problems for marine animals of all kinds, as their bodies are not adapted to warmer and less-salty oceans. With this in mind, we set out to see how warm temperatures, low salinity, and then the combined factors affected our small crustacean friends.

Hermit crabs have little antennules, located between their eyes, which are chemosensory—essentially, they detect tastes and smells. To flick their antennules, they must

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A homeless hermit crab finding his shell again! Video credit: Megan Crofts

be able to contract their muscles rapidly, requiring a lot of systems to be working correctly, many of which require specific temperatures and salt concentrations. Next we popped in some fresh mussel meat for the crab to feast on and timed how long the little guy chomped away on its meal. For our final test, we imitated a predator and scared the little hermit crab out of his shell. This specific to this species of hermit crab, as it will leave its shell quite readily (especially if the shell is too small to be a safe refuge anyway). But it won’t want to be homeless for long, and will be searching for a shell soon.

Interestingly, our results were not significant; meaning we can’t confidently say decreased salinity or increased temperature have substantial impact on these three behaviours in hermit crabs. There are multiple possible explanations for this. Maybe our Vancouverite crabs have adapted to changing ocean salinities because they deal with summertime influx of freshwater into the oceans from the Fraser River. Maybe hairy hermit crabs are uniquely able to withstand salinity and temperature stress. BUT this doesn’t mean that hermit crabs would be happy as a clam in a hot tub, or that you can plop a marine hermit crab in your freshwater fish tank at home and he’ll be okay. Actually, it could be far from it. This experiment could simply mean we weren’t looking at the right thing. Sure, these three behaviours seem to not be impacted by climate change stress, but maybe other really important behaviours will be. Maybe the differences weren’t notable at the temperatures and salinities that we were testing. Science is not so simple that we can look at our (frankly, quite weird) results and say they prove that these adorable hermit crabs will definitely be fine as our planet changes. Sometimes, weird results just give us reason to pause, look at what could’ve gone wrong, and try, try again!

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