Meet Majoid Crabs, the Decorator Crabs!
One defining wonder about this season is the beautiful decorations that are visible everywhere. These ornaments make the season more festive and enhance good feelings. But it seems that decorating is not an exclusively human trait. In fact, decorating is also an innate nature among majoid crabs, also known as decorator crabs.
The decorator crabs are prominent among marine scientists for embellishing their surface with items secured from their surroundings. About 75 percent of majoid crab species are notorious for decorating with bits of sponges, algae and other marine debris.
Marine scientists are still exploring the physical and environmental factors that drive this decorating behavior. To probe this specific area, University of Delaware marine scientist Danielle Dixson and a team of researchers that included undergraduate students studied the majoid species Camposcia retusa. Their aim was to identify the factors that determine patterns of, and investment in, decorating.
The researchers found that the decorating trait of majoid crabs is used predominantly to hide from, or deter, predators. They also made other interesting discoveries about the unique crustacean.
For the study, the researchers placed decorator crabs in individual containers. Water-soaked craft pom-pom shelters were placed in each container. Half of the crabs were given a shelter for habitat to see whether having somewhere to hide affected how much or how fast the crab decorated.
Over a 24-hour period, the team photographed the crabs every hour for the first 12 hours, and at hour 24, and analyzed the images to determine where the crabs decorated, whether they rearranged things and what parts they decorated first.
Here are the surprising results.
In the study, all of the crabs were fully decorated within 24 hours. Most of the crabs were decorated within six hours of having access to the pom-poms. According to Dixson, this manifests that decorating is an important predator adaptation because the crabs do it very quickly.
While other species of decorator crabs adorn their body first, the UD research team’s study showed that Camposcia retusa decorated their appendages (arms/legs) first when a habitat was present.
For decorator crabs that do not have habitat inside the their containers, the researchers found that the crabs decorated everywhere. Aside from that, for the decorator crab, more decoration means the animal requires more energy to move around, and the slower they will be to escape predators.
More Research Needed
The researchers want to conduct ongoing research to determine whether the crabs can actually see and choose items based on color. The researchers are curious whether these deep sea crabs are visually hiding themselves or whether their decorating habits are motivated by smell, known as chemical camouflage.