Land planarians and their snail prey

Land planarians are invertebrate predators having a high specues tichness in the Neotropics, e.g. in the Atlantic Forest ecoregion in Brazil (Boll & Leal-Zanchet, 2016). This recent study brought more details on the food preference of this group.

“Land planarians are recognized as important predators, yet studies on their feeding habits are usually restricted to invasive species. Thus, it is difficult to determine the real ecological role of this group in ecosystems and how their communities are structured. In the present study, we analyzed the diet of six co-occurring Neotropical land planarians and their success in capturing prey, based on experiments in the laboratory, in order to determine how they share resources in the same environment. We also calculated indices of food niche breadth and food niche overlap for land planarians for the first time. The diet of Luteostriata abundans comprises only woodlice and the diets of Obama ficki and Obama ladislavii are composed only of gastropods, while Paraba multicolor and Obama anthropophila feed on both gastropods and other land planarians. An invasive species recently found in Western Europe, Obama nungara, showed the highest food niche breadth, feeding on gastropods, earthworms and planarians. We found the highest niche overlap between O. anthropophila and P. multicolor. The results suggest that land planarians are frequent predators of woodlice and land gastropods in the Neotropical ecozone and thus are important for the maintenance of native ecosystems and for the control of invasive species. The coexistence of several species in the same habitat is possible due to the use of different species as main prey, which reduces interspecific competition”.

schermafbeelding-2016-12-01-om-14-03-31

Since the experiments were done in the laboratory, the authors had control on the prey species they offered to the planarians. For gastropods these were: Bradybaena similaris, Helix aspersa, Deroceras laeve, Sarasinula plebeia, and Belocaulus sp. These are all medium-sized species; it would be interesting to know if the planiarians also are predators of the larger sized species occurring in the region (Strophocheilidae, Megaspiridae), and to what extent they are a threat to endangered, native species in the Atlantic Forest.

Reference:
Boll, P.K. & Leal-Zanchet, A.M., 2016. Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest. – Zoology 119: 162–168.

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