Why everything eventually becomes a crab

The idea of evolution is fairly strange. Who knows how our ancestors will appear in millions of years; they undoubtedly didn't resemble modern humans when they lived on Earth millions of years ago. However, if you believe some recent memes, our descents can appear a little grumpy.

The joke, which states that everything will ultimately resemble a crab, is based on a true statement. Because the crab form has changed so frequently, scientists had to coin the term "carcinization" to describe it.

The evolution of humans into crabs is probably not in the cards, but it has happened several times in the crustacean family. Creatures that began life looking like lobsters or hermit crabs eventually evolved into the low, round, pinchy bugs we all know and love. But first, let's define the word "crab" before we explore the reasons why this is.

The first image that comes to mind when you hear the term "crab" is generally something that resembles a blue, king, or Dungeness crab. They have a small, flat, roundish, or square body form, a concealed abdomen on the underside of the crab, and a hidden tail in place of the muscled visible tail that is typical of lobsters. This gives them a distinctive and unforgettable appearance.

When you observe this rounded, somewhat oval form, Jo Wolfe, a research associate at Harvard's department of organismic and evolutionary biology, claims that "your eye is detecting a crab."

However, only two of the three species of crab—the blue crab, the king crab, and the Dungeness crab—are considered to be "real crabs" or brachyurans, a suborder of the decapod order that also includes shrimp, lobsters, and crayfish. The king crab, which is essentially the traditional form, really belongs to the Anomura or "false crab" group, which is closely connected to this unusual family.

"These two definitions of the word become confused," claims Gerhard Sholtz, a crustacean biologist at Berlin's Humboldt-Universität who just resigned. "I'd argue not all crabs are crabs,"

According to Wolfe, brachyurans, unlike anomura, are assumed to have originally had a crab-like morphology. Anomura, though, weren't always thus way. Consider the hermit crab, which is the ancestor of the king crab. Although it has "crab" in its name, its swirling abdomen and delicate exoskeleton are everything from crab-like.

However, carcinization doesn't exclusively occur in this situation. Even though they are not really "genuine crabs," porcelain crabs and hairy stone crabs have a similar appearance. We don't really know how often it's happened, says Heather Bracken-Grissom, an expert on marine invertebrates and an associate professor at Florida International University, because carcinization is still a relatively unknown process involving an animal evolving toward a set of crab-like characteristics, and there isn't a hard yes or no definition of crab-look-alikes. Some species, like the squat lobster, may only be partly carcinized, giving them a half-crab, half-lobster appearance.

In addition to how frequently a species has erred on the cranky side, one must also consider why they would do so in the first place. With the aid of an NSF grant, Wolfe and Bracken-Grissom are currently attempting to determine that.

According to Bracken-Grissom, "There has to be some sort of evolutionary benefit to having this crablike morphology." The advantages of having a crab form are still unknown, but according to researchers, they could have something to do with the capacity to colonize new environments or diversify into new species. After example, compared to only a few lobster species, there are over 6,000 distinct species of Brachyurans scampering throughout the earth.

Even if the internet may want it to be, having a crab shape is not truly a "final form," according to Wolfe. There is undoubtedly something occurring in the world that is driving crustaceans towards crabbiness. The process of evolution is far from simple, and it will continue to occur forever. The crab form may become out of fashion during the course of the next million years, and crustaceans may 'decarcinize' and migrate away from it.

Therefore, while the final evolutionary body shape may still be a mystery, it is hoped that this will not be the case very soon for the reason decopods continuing evolving into crabs.