Mind the food: Survival, growth and fecundity of a Neotropical land planarian (Platyhelminthes, Geoplanidae) under different diets.

Although most land planarians are sensitive to environmental changes, some species are well adapted to human-disturbed areas and are easily transported to new places, having the potential to threaten native ecosystems. We investigated growth and survival in a land planarian common in human-disturbed areas in southern Brazil. Specimens of Obama anthropophila were divided into three groups that received different diets: (1) only the land planarian Luteostriata abundans (N=13), (2) only the slug Deroceras leave (N=12), and (3) alternating both prey types (N=13). We monitored the weight of the specimens for a month and counted and weighed egg capsules. Planarians receiving a mixed diet tended to survive less than the groups receiving a single prey type; there were significant differences between those feeding on D. laeve and the other groups. Planarians with the mixed diet ate L. abundans more often than D. laeve, and those feeding only on L. abundans tended to eat more than the other groups. Most egg capsules were laid by specimens with a diet based on D. laeve but the mixed-diet group laid heavier capsules. Both prey species are suitable as food for O. anthropophila, although it prefers planarians when both food items are available. The constant alternation between food items seems to have adverse effects, perhaps related to physiological changes to digest different food items. The heavier egg capsules of the mixed-diet group, considering its lower survival, suggest terminal investment, i.e., an increased reproductive effort when approaching death. The ability to feed on both snails and planarians, combined with its proximity to humans, make O. anthropophila a potentially invasive species.