Decking the claws—Majoid crabs adorn their surfaces with colorful ‘ornaments’ | The American Ceramic Society

Decking the claws—Majoid crabs adorn their surfaces with colorful ‘ornaments’

CTT 12-26-majoid crab

[Image above] Camposcia retusa, a species of decorator crabs, are well-known for adorning their surface with objects such as sponges and algae. Credit: University of Delaware

Each year, just like clockwork, Black Friday is no sooner over when holiday decorations start appearing in homes, retail stores, and pretty much everywhere you look. And even though Christmas is over, most of us will likely keep our halls decked through New Year’s. We humans have this decorating skill down to a science!

Obviously the animal kingdom has no conception of holidays, let alone Christmas. There are probably a number of very patient cats and dogs who are forced to wear embarrassing outfits solely for their owners’ amusement. And obligatory social media photos.

And then there’s the marine animal that decorates its surface with colorful marine embellishments. But not because they’re feeling the holiday spirit.

Camposcia retusa, a species of Majoid crabs, are known to “decorate” their outer surfaces with items from their immediate surroundings—such as sponges, algae, and other organic waste.

Researchers from the University of Delaware are currently studying the decorator crab to identify behavior patterns of adorning its shell with surrounding marine debris. Led by marine scientist Danielle Dixson, assistant professor in the Marine Biosciences department, the team conducted experiments with several crabs by separating them into individual containers and giving them “decorations”—not the type from their environment that crabs typically use, but small synthetic pompoms.

Scientists suspect that decorator crabs exhibit this behavior in order to disguise themselves from predators, according to a news release from the University of Delaware.

“The decorator crab is a perfect study example because the IndoPacific species has velcro-like substances on its shell and hooks on its appendages that enable it to secure items on its exterior,” Dixson says in the release.

The researchers provided half of the crabs with a shelter of their habitat to see if it had any effect on its decorating speed. Within a 24-hour period every crab was decked out in pretty pompoms. Most donned their pompoms within six hours.

Their observations during the period indicated that the crabs not only decorated themselves quickly, but those placed in habitats adorned their arms and legs first. Dixson believes they do this to cover up the appendages that protrude from their bodies when they go into hiding.

Another variable affecting decorating was in the habitat. The crabs that weren’t provided a habitat decorated everywhere, Dixson explains. In other words, the presence of a habitat is a factor in where on their bodies Camposcia refusa decorate.

She and her team will continue their research to determine if the scent of other animals, especially predators, can determine decorating habits and behavior.

Their paper, published in Behavioral Ecology is “Shelter availability mediates decorating in the majoid crab, Camposcia retusa” (DOI: doi.org/10.1093/beheco/arx119).

Watch the video below to observe this interesting creature.

And watch this video to see how a decorated Camposcia retusa hides and blends in to its surroundings.

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