Crab
If you’re on the internet as much as I am and have spent a good amount of time applying for jobs or creating new accounts for various websites, you’ve probably run into those CAPTCHA tests that range from “type out this sequence of letters and numbers back to us” to what I more commonly see with “click on all images that contain a bunny”. Hopefully, you have a good mental model of what this looks like. If not, here’s an example of one:
As a computer science major in college and now teaching computer science to BIPOC youth, I would most likely take this in a route that talks about maybe the pros and cons of a CAPTCHA. Do I think these are actually helpful? What are the accessibility issues that come with this? WHAT CONSTITUTES AS CONTAINING THE TRAFFIC LIGHT HUH? THERE’S A GREY SMIDGE THERE DOES THAT COUNT?
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Nah, let’s talk about crabs.
The only reason I mentioned CAPTCHAs is for this next activity. I’m going to show you some photos. Please personally select which ones you think are true crabs (If you’re confused about why I added the word true, don’t worry I’ll explain soon).
And to help you out I’ve given the corresponding name of each creature:
Atlantic Ghost Crab
Hermit Crab
Spider Crab
Horseshoe Crab
Red Land Crab
Angular Crab
Blue Crab
King Crab
Porcelain Crab
This is a filler
So you won’t see the answers
And it’s a haiku
And the results are:
Atlantic Ghost Crab - TRUE CRAB
Hermit Crab - FALSE CRAB
Spider Crab - TRUE CRAB
Horseshoe Crab - FALSE CRAB
Red Land Crab - TRUE CRAB
Angular Crab - TRUE CRAB
Blue Crab - TRUE CRAB
King Crab - FALSE CRAB
Porcelain Crab - FALSE CRAB
So what’s happening here? Every single one of these animals has the word “crab” in its name, so how are some of them false crabs?
Every animal shown above can be identified as a member of two sister infraorders of creatures, Brachyura and Anomura. And upon initial observation, there seems to be no need for there to be a difference between the two different groups. But upon further investigation, we can see the main difference where true crabs have four pairs of walking legs while the others only have two or three. And then while the ones I chose look like crabs, others parts of Anomura have a varying range of how they look.
So then it’s like alright, they’re part of different families, what’s the big deal? Honestly, for the average person, I don’t think this is that big of a deal. Crabs do not have that much of an impact on us besides being a good meme and source of food.
But the wild thing here is that for the four creatures listed above as false crabs if we look at their ancestors, we would see that they would look nothing like the true crab we’re so used to. Take the king crab, prized for being enormous and delicious. If we looked at its evolutionary history, we would see that it evolved from a hermit crab.
This process happens enough that it actually has a name: carcinisation/carcinization. And my favorite part of this whole thing is that we don’t know why it happens yet. For some reason, at some point in time, these creatures just found it more favorable to adopt the features of a crab than to stay how they were. They seem to know something about crabs that we just don’t yet and it’s such a wild thing to see happen. But what’s also interesting is that there’s no decision saying that crabs are done evolving. If the true crabs start evolving to develop new features, will the creatures in Anomura follow suit? Or will we see something completely new?
If you were hoping for maybe a lesson or deeper meaning to arise from all this talk about crabs, I’m gonna have to rain on your parade. I just wanted to talk about crabs. That’s all.
