The Curious Case of Strange Orange Tufts

Have you ever woken up on a Wednesday morning and wondered what it would be like to blow a gentle breath directly into the eyes of a green shore crab? If so, hold on for just one moment before you pack your bags and head down to the beach.  This week in the lab we conducted several experiments in order to examine the behaviour of green shore crabs, Hemigrapsus oregonensis, and as it turns out, nothing exciting happens when you blow on them.


Green Shore Crab
Photo Credit: Walter Siegmund

You may be wondering what prompted us to blow on our crabs, and I can assure you it wasn’t a poor attempt at flirting. It all started a couple weeks ago when we were examining the effects of ocean acidification on the cold tolerance of the crabs. During this experiment we noticed that some of the crabs had this strange orange tuft on the underside of their claws, and after asking around for a little while it appeared as though nobody had a clear idea of what they were. As Fred Jones from the cartoon Scooby-Doo would say: “Gang, we have a mystery on our hands!”



Orange tuft on the underside of the green shore crab’s claw
Photo Credit: Jon Howe

Upon scouring the internet for a few days we came across one single paper published in May of 1971 that suggested these tufts may be used to either moisten the eyes when they became too dry, or to brush debris out of the way. With this in mind we immediately began collecting crabs to start our experiments. We quickly noticed that only the male crabs had these tufts, so we put our lovely ladies back in the holding tank and promptly got started with the men. After several hours of blowing on the crabs and dropping sand into their eyes, we failed to provoke any wiping or moistening behaviours from them. Saddened and defeated, we put the male crabs back into their tanks and the mystery of the strange orange tufts remained unsolved.

Despite the results of the orange tuft experiment, the day was not a complete loss. Many of the other groups working in the lab found some pretty cool stuff. Not only did we discover that crabs appear to be spatially aware of themselves and their ability to fit through tight spaces, we also learned that crabs only tend to seek out hiding places when they are underwater, and will instead remain completely still when on land. These findings are important for understanding the behaviours and interactions between organisms in an ecosystem, and can lead to exciting new developments in the future.

If you’d like to know more about the mysterious orange tufts on the underside of the green shore crabs, check out this paper written by Charles C. Naughton:



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