Preliminary study of the scars borne by Gammaridae (Amphipoda, Crustacea)

Many gammarid shrimps from the rivers Meuse and Viroin bear scars. A recent invader in the Meuse, Dikerogammarus villosus, is claimed to exhibit a strong predatory behaviour against other Gammaridae. Therefore we tested the hypothesis that scarred Gammaridae should be more numerous in the Meuse where D. villosus is dominant than in a tributary, the Viroin, where it is absent. On the contrary there were significantly more scarred individuals in the Viroin (51\%) than in the Meuse (32\%). The most exposed appendages were the most frequently injured, and multiple scars on a single individual were not distributed randomly. These results are discussed.