A new study has revealed that ocean acidification, caused by climate change, destroys the Dungeness crabs' sense of smell. Such findings partially shed light on the population decline of these species and may have grave consequences for marine life.

Dungeness Crabs

SciTechDaily reports that Dungeness crabs hold remarkable economic importance. They are among the most popularly eaten crabs. Their fishery was even appraised at over $250 million back in 2019.

Similar to other crabs, these Dungeness crabs do not have excellent vision. Because of this, their sense of smell is extremely vital for them to navigate around and search for food, suitable habitats, and mates. This sensory capacity also helps them avoid predators.

Such creatures sniff through a procedure called flicking. In such a process, the crabs flick their tiny antennas through the water in order to pick up smells. These antennules carry small neurons that are responsible for the creature's sense of smell. These neurons then deliver the electric signals to the brain.

Now, a new study has shown that climate change has directly affected this very important survival function of Dungeness crabs.

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Dungeness Crabs Are Losing Their Sense of Smell

More specifically, climate-change-caused ocean acidification has made Dungeness crabs physically sniff less, affected their ability to pick up food smells, and decreased the activity of those sensory nerves that manage smell.

Cosmina Porteus, a co-author of the study and an assistant professor from the Department of Biological Sciences from the University of Toronto, notes that this is the first research to examine how ocean acidification physiologically affects crabs' sense of smell. The study was published in the Global Change Biology journal.

According to a statement from the university, oceans across the globe are turning more acidic due to their increased absorbance of atmospheric carbon dioxide. Ocean acidification directly results from carbon pollution and fossil fuel burning. Many studies have also demonstrated how it affects marine wildlife behavior.

When the Dungeness crabs got exposed to ocean acidification, the researchers were able to observe two things. Firstly, the creatures were observed to flick less; and secondly, their sensory neurons' responsiveness to odors was hampered by 50%.

Though crabs typically flick more when they pick up an interesting odor, this was not the case for crabs that got exposed to ocean acidification. For the behavior to surface, the odor had to have a concentration that was 10 times higher, notes Porteus.

SciTechDaily adds that there are some possible reasons as to why ocean acidification seemingly affects these crabs' sense of smell. Porteus notes a prior study that demonstrated how ocean acidification hampers the molecules of odor. This, in turn, affects how they bind to receptors of smell in marine creatures, including crabs.

Porteus, along with co-author and post-doctoral researcher Andrea Durant, tested the sensory neurons' electrical activity to see their reduced responsiveness to smells. The researchers also observed that there was a decreased number of receptors and that sensory neurons were getting smaller by as much as 25%.

Such sensory neurons are active cells; and if they are not picking up as much smell, they could be shrinking in order to save energy.

Decreased detection of food could also affect other species that are economically valuable, such as snow crabs and Alaskan king crabs. This is because their olfactory functions work in the same way.

Porteus also adds that this could partially explain the population plummet. Due to their problems finding food, female crabs may not have much energy for egg production.

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