A taste for exotic food: Neotropical land planarians feeding on an invasive flatworm

Invasive species establish successfully in new habitats especially due to their generalist diet and release of natural enemies. However, native species may also adapt to use new elements in their ecosystem. The planarian Endeavouria septemlineata, first recorded in Hawaii, was later registered in Australia and Brazil. Recently we found it in human-disturbed areas in southern Brazil and here we investigate its interactions with other invertebrates both in the field and in the laboratory. We observed the species in the field during collecting activities and maintained some specimens alive in small terraria in the laboratory, where we offered different invertebrate species as potential prey and also put them in contact with native land planarians in order to examine their interaction. Both in the field and in the laboratory, E. septemlineata showed a gregarious behavior and was found feeding on woodlice, millipedes, earwigs and gastropods. In the laboratory, specimens did not attack live prey, but immediately approached dead specimens, indicating a scavenging behavior. Four native land planarians of the genus Obama and two of the genus Paraba attacked and consumed E. septemlineata, which, after the beginning of the attack, tried to escape by tumbling or using autotomy. As a scavenger, E. septemlineata would impact the populations of species used as food, but could possibly exclude native scavengers by competition. On the other hand, its consumption by native land planarians may control its spread and thus reduce its impact on the ecosystems.