Some Crabs Are Dressing Up Themselves In Fashionable Way

Some Crabs Are Dressing Up Themselves In Fashionable Way

Snorkeling seems like a nice idea to do in a hot summer holiday, especially when you choose to spend the holiday near tropical beaches. We are not going to talk about the activity this time, but rather about strange creatures you can find while doing it.

Down at areas where corals live, you might notice some creatures creeping slowly in a shape you have never seen before. Is it a new species of sea animal, or is it an alien larva trying to conquer the world in the future? Most likely not, it is just another kind of crab.

Don’t be too surprised, because that creature might just be another species of crab named decorator crab. Almost every decorator crab appears different from one another, because they have their own ‘aesthetic’ about their appearance.

But it is not a surprising thing in the world of crabs. Apparently, there are about 7000 different species of crabs with their own taste of aesthetics. This is an interesting topic to talk about, and here in this article we are going to talk about it.

Why Do They Do It?

Decorator crab by prilfish
Decorator crab by prilfish

As said before, about 7000 different species of crabs ‘dress up’. It brings us wondering why is it that those crabs are dressing up. Actually, the reason varies but most of the time they ‘dress up’ to protect themselves from dangers. The question is, whether any of those crabs are dressing up for aesthetic reasons?

Well, to say whether the marine animals are going for the artsy reason or not is difficult, but some of them are ‘very picky’ as Jay Stachowicz said. Being a marine ecologist at the University of California at Davis, Stachowicz has spent a great amount of time to understand about the marine animal’s behavior.

Although many species of crabs are decorating their shell in such an ‘artsy’ way, but different crab has its own different taste. “What they wear depends on the species. Some are very picky. They protect themselves from predators by using toxic algae or stinging sea anemones,” Stachowicz said.

Decorator crabs prefer seaweed to decorate their carapace, and they keep changing the decoration according to the season. It might seem like what we human do to follow the latest seasonal fashion model, but in decorator crab’s case the reason is for survival.

Using the latest fashion is the best way for decorator crabs to disguise itself from hungry seagulls. By decorating their shells with current season’s seaweed, they can blend pretty well with the environment.

How To Dress Up

Decorator crab by Ruth and Dave
Decorator crab by Ruth and Dave

Most humans dress up because they mean to be seen, while most crabs are dressing up their shells to hide from outside threats. However, some crabs are doing it because they want to be seen. The motives differ depends on their environment.

Researchers at the University of Delaware found out about this fact when they conducted a study back in December 2017. They tested how decorator crabs cover themselves up with decorations by putting ‘nude’ crabs inside water-filled tanks with pom-pom-like decorations.

Half of those tanks contained only water and the decorations, while the other half also provided some kind of housings for the crabs. The housings that the researchers gave the crabs simulated a cave or burrow to hide themselves.

The crabs which had a place to hide decorated their claws first, and decorated the rest of their bodies after. Claws are the parts which most likely to stick out the door first, meaning by decorating it first those crabs meant to be seen.

Different thing happened to those which were exposed. The crabs put in tanks without hiding places covered their bodies with the pom-poms right away without prioritizing any special parts. From this research, scientists concluded that defense is a primary motive.

Moss Crab And Its ‘Dog’

Moss crab by jkirkhart35
Moss crab by jkirkhart35

The case is different with Moss Crab (Loxorhynchus crispatus). This crab is surely have its own favorite ‘decoration’, and love to keep it for the whole time. Moss Crabs stick anemones, sponges, seaweed, and other kind of decorations to their shells since the earliest stage of their lives.

Being attached to the shell of a moss crab, the anemones are given the benefits of being mobile. By hitchhiking on the shell of a crab, the anemones can get more food than being stationary in just one place. In order to return the favor, the anemones can help the crab protect itself from outside threats by stinging that touches them.

What’s unique from this relationship between Moss Crab and anemones is, whenever the crab sheds its shell it takes the anemones out from the old shell and attach them into the newer shell. No wonder in many occasion the crab live together with the same group of anemones from the beginning of its life until the end.

We can also say that the interaction is pretty similar to humans and dogs. But there is also a chance that they find those anemones give them good looks. Like we just want to wear our ‘lucky clothes’ in any occasion to increase our luck.

So, is it because the crabs are ‘in love’ with the anemones, or because they are too lazy to find other group of anemones? Researchers are still finding out about the real reason, but so far the most rational reason is to protect themselves from medium-sized predators using the anemones’ stings.

Advanced Decoration

Sponge crab by berniedup
Sponge crab by berniedup

Whatever the motives are, but researchers are pretty amazed by how crabs can be so advanced in disguising themselves. Those which used to disguise themselves even have developed some physical features to support their ‘party costume’.

In example, sponge crabs can use their back pair of legs to hold the sponges, which is the costume they prefer for the party, all over their bodies. Stachowicz said that the crabs even “often shape the sponge to fit over a large part of their carapace”.

While the decorator crabs have developed some kind of velcro-like hairs all over their carapace to hold the decorations in place. By developing this velcro-like hairs, decorator crabs can modify the decorations anytime yet the decorations won’t set loose.

Some of them even use their ‘party costumes’ in advanced ways. Carrier crabs, which can be found in Indo-Pacific and East Africa, use their back legs to hold sea urchin when they feel like traveling. By using the urchin’s venomous spines, the crab uses it as a kind of venomous shield to ward off predators.



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