Ectozoochory as a possible vector enhancing the spread of an alien amphipod Crangonyx pseudogracilis

Most studies of biological invasions refer to the human role in species dispersal but the importance of ectozoochory has scarcely been studied. Thus, we investigated whether the first alien amphipod species found in the Iberian Peninsula, North American Crangonyx pseudogracilis can be dispersed by waterfowl. To do this, we showed experimentally that the amphipod may cling to the plumage and legs of a mallard duck (Anas platyrhynchos) and be transported under controlled laboratory conditions. The probability of the amphipods being transported on duck's plumage or feet is 1.84 and 1.6%, respectively. Another experiment showed that C. pseudogracilis may stay attached to a flying duck and survive during its flight for a distance of 6.8 km. In addition, we found that this invader can stay alive with a LT90 of 88.6 min when exposed to desiccation. Thus, we conclude that C. pseudogracilis may be successfully transported by the waterfowl for short distances to other waterbodies. Thus, ectozoochory may be an important way of spreading the amphipods in areas where the hydrological network is poorly developed and not interconnected with artificial canals.