Photo of a Boxer Crab (or Pom Pom Crab), Lybia edmondsoni by Dave Harasti
In one of Brian Brock’s many letters to me in 2014, he wrote, “I am pretty sure that at some stage in my (chequered) career , I have seen a photo of a crab holding an anemone in each claw. (It ) Could have been seen in an aquarium rather than just a photo (e.g. Scripps, or NZ, or Sydney).
Look as I might, I could not find a photo, as a reference to this behaviour. I wonder whether any of the aquarium buffs or more experienced divers have ever seen a crab holding an anemone. The next question would be “Is the behaviour characteristic of a particular species of crab, or more general?”
In what way are the anemones being used? Defence? Camouflage? Or simply an efficient plankton net, via which, a crab might score some plankton dainties for a meal?
I had assumed that anemones associating with crabs would benefit from the untidy feeding habits of the crabs, not the other way around.
I don’t know how a victim would react if cuffed in the ear by a claw-held anemone, or whether it ever happens.
Anemones in the same aquarium as crabs might find it a bit claustrophobic.”
My web search led me to a YouTube video by Maikel Sanders titled “boxing crab or boxer crab or pom pom crab pregnant”.
A boxer crab is a very funny looking little crab (2cm max). The video footage shows crabs with two little white anemone boxing gloves. One of the players is pregnant and walks around with eggs under her mouth.
According to Wikipedia “Lybia edmondsoni is a species of small crab in the family Xanthidae and is endemic to the Hawaiian Islands. Like other members of the genus Lybia, it is commonly known as the pom-pom crab or boxer crab because of its habit of carrying a sea anemone around in each of its claws, these resembling pom-poms or boxing gloves. Its Hawaiian name is kūmimi pua, meaning “inedible flower crab”. In ancient times, this animal was used by sorcerers.”
According to Marinebio, “Mutualism is a symbiotic relationship in which both species benefit. For example, some anemones share a mutualistic relationship with Boxer crabs, Lybia tesselata.
Lybia tessellata
(Source: http://en.wikipedia.org/wiki/Lybia_tessellata#mediaviewer/File:Xanthidae_-_Lybia_tessellata.jpg )
The Boxer crab holds the anemone in its claws to use its stinging tentacles to fend off predators. In turn, the anemone consumes the crab’s leftovers.”
According to Wikipedia “Lybia edmondsoni is a species of small crab in the family Xanthidae and is endemic to the Hawaiian Islands. Like other members of the genus Lybia, it is commonly known as the pom-pom crab or boxer crab because of its habit of carrying a sea anemone around in each of its claws, these resembling pom-poms or boxing gloves. Its Hawaiian name is kūmimi pua, meaning “inedible flower crab”. In ancient times, this animal was used by sorcerers.”