The significance of chelae in the agonistic behaviour of the white-clawed crayfish, Austropotamobius pallipes

As in other benthic decapods, crayfish have chelae that are important for i ntra-specific agonistic encounters. In Austropotamobius pallipes, scars and mutilations are present mostly on the chelae, these being the main targets of agonistic contacts. Because males participate in more aggressive intera ctions than females do and compete with other males for acquiring females i n escalating contests, selection for large chelae should be stronger in mal es. Thus, in A. pallipes (i) chelae are longer, wider and higher in males t han in females; (ii) chelar size in males increases allometrically with cep halothorax length; (iii) male specimens are more often deprived of at least one cheliped and (iv) large males have the highest frequency of scars. Mal es with one regenerated cheliped, when opposed to a competitor with both la rge chelipeds, display the same motivation to fight, but perform less chela e threat displays than normal crayfish and immediately get a lower hierarch ical rank. In these contests, Resource Holding Potential (= chelar size) is highly different between the crayfish and the information of this asymmetr y is correctly transferred between the two opponents.