Carnivore mollusks as natural enemies of invasive land flatworms.
There are several records of the carnivorous behaviour of land flatworms, considered to be top-predators in their micro-habitats, by preying upon various species of invertebrates. However, there is little knowledge of predators on land-flatworms. The possible impact of invasive land flatworms on prey populations has caused widespread concern, when considering their predatory behaviour, combined with recent human influence on the distribution of certain species. This work is the first record of predation on land flatworms by a carnivorous snail. Various-sized land flatworms of 10 native species of the subfamily Geoplaninae, as well as the exotic species Bipalium kewense (subfamily Bipaliinae), were offered to Rectartemon depressus (Gastropoda, Streptaxidae), which accepted all. The predator also fed on the snail Bradybaena similaris. The snails were maintained in laboratory for an average period of 12 months based on a mixed diet of flatworms and B. similaris, suggesting that the snail is a polyphagous predator. Because certain land-flatworm species have been described as invasive species which may have a potential impact on prey populations in native and man-made ecosystems, it is proposed that carnivorous snails of other native species, as potential predators of flatworms, should be tested for possible use in biological control programmes of these invasive planarians.