Crayfish fight club

Yabbies (Cherax destructor) are pugnacious little devils. But when you pick fights all the time, it's handy to have a memory for faces. Saves getting your telson kicked a second time.

A paper published recently in PLoS ONE shows that yabbies can not only recognise the faces of sparring partners but remember them for a day or more. (Memory is better in the vanquished than the vanquisher.)

How do they tell each other apart? Face width seems to be important. The little crusties can tell a fat head from a narrow one. Other characteristics play a role but zoologists at the University of Melbourne suggest that it's the combination rather than a specific feature that helps in yabby-to-yabby identification.

The face of C. destructor. (a) Features analyzed on a yabby's face. Colour hue and saturation taken from the mean of 5 points. (2 marked by white triangles.) (b) PCA factor analysis of facial features.

You can read the paper (including details of how the researchers dolled up their experimental animals in lippie and eye shadow carefully marked the animals to change their appearance) here .

Reference
Van der Velden, J, Zheng, Y, Patullo, BW & Macmillan, DL. (2008). Crayfish recognised the faces of fight opponents. PLoS ONE 3(2): e1695. Published online 2008 February 27. doi: 10.1371/journal.pone.0001695.