Boxer crabs acquire anemones by stealing from each other, and splitting them into clones

Date: January 31, 2017

Source: PeerJ

Researchers have described a little known yet fascinating aspect of the behavior of Lybia crabs, a species which holds sea anemones in each of its claws (behavior which has earnt it the nickname 'boxer' or 'pom-pom' crab). In a series of experiments, they showed that when these crabs need an anemone, they will fight to steal one from another crab and then both crabs will split their anemone into two, creating identical clones.

Lybia crabs were first described in the 19th century, with only a handful of scientific publications since then, mostly dealing with morphology and occurrence, and less with their curious 'anemone wielding' behavior. Although quite common in the aquarium trade, the lack of attention given to them by the scientific community is presumably due to their small size and cryptic behavior.

In a new study, published today in the open access journal PeerJ, Yisrael Schnytzer and Yaniv Giman, both graduate students working under the supervision of professor Yair Achituv at Bar-Ilan University in Israel, and professor Ilan Karplus at the Volcani center, investigated various aspects of the crab-anemone association. Their study focused on trying to resolve a long-standing mystery -- how the crabs acquire their sea anemones.

Over the course of several years more than 100 Lybia crabs were observed or collected from the shallow waters of the Red-Sea on the south shore of Israel in Eilat. These crabs are no more than a couple of centimeters across and have a similar color to the boulders under which they live -- hence even finding them was a task in itself. Throughout the entire study, every single crab was found holding a pair of sea anemones which were identified as belonging to the genus Alicia, probably a newly recorded species.

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