Are hermit crabs stressed out by climate change?

The world’s oceans are expected to undergo some changes due to global climate change. Shifts are already happening now, but are expected to become more pronounced in years to come. Currently, in some parts of the world we are already seeing water temperate changes, ocean acidity dropping, and ecological shifts in environments.

Currently, scientists are investigating the effects climate change could potentially have on organisms and habitats of the worlds’ oceans. Initially in climate change studies, scientists manipulated a single variable- for example, temperature. But the reality of global climate change is it will not only affect a single aspect in the world’s oceans- it will likely affect multiple. Climate change is predicted to shift environments’ temperature, salinity, acidity, oxygen levels, and more. It is important to investigate the effects multiple stressors could have on organisms to fully understand the extent to how climate change will affect these organisms and alter ecosystems.

We set up a fully factorial design, a study design that allows us to test multiple stressors on an organism, on the intertidal hairy hermit crab, Pagurus hirsutiusculus. We exposed hermit crabs to high temperature, low salinity, and a treatment where they received both stressors- high temperature and low salinity. Temperature and salinity stress are expected in the worlds’ oceans in future centuries.

In our first experiment, we counted the number of antennule flicks for 30 seconds. Antennules are used to sense chemicals in the water, it lets the hermit crabs know where there might be food or a predator. There was more antennule flicking in the high salinity than lower salinity treatment in both high and low temperatures tested. This might suggest that muscular activity is affected by salinity, that hermit crabs may be better able to move and contract their muscles at higher than lower salinities.

In our second experiment, we recorded the amount of time a hermit crab spent feeding on mussel tissue in 10 minutes. Stressful environmental conditions could affect an organisms’ feeding rate but we found no trends in feeding times in either temperature or salinity treatments.

hermit crab

A hairy hermit crab, Pagurus hirsutiusculus, eating mussel tissue. Photo: Brittany Ng

In our final experiment, we removed hermit crabs from their shells and recorded the time it took to return to their shell. Seeking a shell is important for hermit crabs because they provide protection from predation and help retain moisture. Temperature and/ or salinity stress could affect the hermit crabs’ ability to detect a shell in its environment or the need to seek shelter may become stronger when the organism is stressed. However, we found no trends in the time it took to find a shell between any of the treatments of temperature or salinity.

Being an intertidal organism, hermit crabs may already possess strong adaptations to large fluctuations in temperature and salinity and are largely unaffected by them because they experience these changing conditions daily. Perhaps intertidal species, like the hermit crab, will be excellent and successful competitors in changing ocean conditions due to global climate change.



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