Lybia Research Articles

Boxer crabs induce asexual reproduction of their associated sea anemones by splitting and intraspecific theft.

Crabs of the genus Lybia have the remarkable habit of holding a sea anemone in each of their claws. This partnership appears to be obligate, at least on the part of the crab. The present study focuses on Lybia leptochelis from the Red Sea holding anemones of the genus Alicia (family Aliciidae). These anemones have not been found free living, only in association with L. leptochelis. In an attempt to understand how the crabs acquire them, we conducted a series of behavioral experiments and molecular analyses. Laboratory observations showed that the removal of one anemone from a crab induces a “splitting” behavior, whereby the crab tears the remaining anemone into two similar parts, resulting in a complete anemone in each claw after regeneration. Furthermore, when two crabs, one holding anemones and one lacking them, are confronted, the crabs fight, almost always leading to the “theft” of a complete anemone or anemone fragment by the crab without them. Following this, crabs “split” their lone anemone into two. Individuals of Alicia sp. removed from freshly collected L. leptochelis were used for DNA analysis. By employing AFLP (Fluorescence Amplified Fragments Length Polymorphism) it was shown that each pair of anemones from a given crab is genetically identical. Furthermore, there is genetic identity between most pairs of anemone held by different crabs, with the others showing slight genetic differences. This is a unique case in which one animal induces asexual reproduction of another, consequently also affecting its genetic diversity.

Bonsai anemones: Growth suppression of sea anemones by their associated kleptoparasitic boxer crab

Kleptoparasitism, the theft of food, is a foraging strategy often overlooked or misinterpreted as a commensal association. Crabs of the genus Lybia, commonly known as boxer crabs, hold a pair of tiny sea anemones in their claws. The nature of this seemingly commensal association has never been tested empirically. In a laboratory study of food consumption, we show that the boxer crabs Lybia leptochelis regulate the size of their claw-held sea anemones (Alicia sp.). The anemone size is regulated by: (a) distancing the held anemones from presented food – and in the event any food particles are caught – (b) using rapid leg movements to remove most of the food captured by either anemone. Anemones removed from the crabs and grown independently underwent remarkable changes in morphology, color, and size, with over 250% expansion in pedal-disk diameter. The ultimate aim of classical kleptoparasitism is food acquisition by the pirate. We have shown a completely new role of kleptoparasitism, in which the victim is not only robbed of food, but is also regulated in size. The boxer crab thus maintains a “Bonsai” symbiont that is conveniently carried around as a tool to trap its food and provide protection.

The Polydectinae Dana, 1851, of the Philippines, with description of a new genus for Lybia hatagumoana Sakai, 1961 (Crustacea: Decapoda: Brachyura: Xanthidae)

The xanthid subfamily Polydectinae Dana, 1851, is recorded for the first time in the Philippines, being represented by four species: Polydectus cupulifer (Latreille, in Milbert, 1812), Lybia tessellata (Latreille, in Milbert, 1812), L. leptochelis (Zehntner, 1894), and L. hatagumoana Sakai, 1961. The taxonomy of L. hatagumoana is discussed at length, and a new genus, Tunebia gen. nov., established for it and the allied L. tutelina Tan & Ng, 1994, from New Caledonia. The new genus is diagnosed and compared with other polydectine genera.