@article {292, title = {High Predation Pressure by an Introduced Flatworm on Land Snails on the Oceanic Ogasawara Islands}, journal = {Biotropica}, volume = {39}, number = {5}, year = {2006}, pages = {700-703}, chapter = {700}, abstract = {

The introduction of a predatory flatworm, Platydemus manokwari, has been considered a cause of the decline of endemic land snails on the tropical oceanic islands. To clarify the effect of P. manokwari on land snail survival in the field, we examined survival rates of snails experimentally placed in areas where snails are absent (i.e., P. manokwari is present) on Chichijima, Ogasawara (Bonin) Islands. We found that over 50 and 90 percent of the snails were dead after 3 and 11 d, respectively, and that the main cause of mortality was predation by P. manokwari.

}, doi = {10.1111/j.1744-7429.2006.00196.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1744-7429.2006.00196.x/abstract}, author = {Sugiura, S. and Okochi, I. and Tamada, H.} } @article {286, title = {Potential impacts of the invasive flatworm Platydemus manokwari on arboreal snails}, journal = {Biological Invasions}, volume = {11}, year = {2009}, pages = {737-742}, chapter = {737}, abstract = {

The introduction of the snail-eating flatworm Platydemus manokwari (Tricladida: Rhynchodemidae) has been considered a cause of the extinction of native land snails on several Pacific islands. Although P. manokwari is known to attack land snails on the ground, whether P. manokwari attacks snails on trees remains unclear. To clarify the effect of P. manokwari on arboreal snails, we examined survival rates of land snails experimentally placed on tree trunks (0.5\–2.0 m above the ground) in a forest on Chichijima, Ogasawara (Bonin) Islands, in the northwestern Pacific Ocean. The survival of snails experimentally placed on tree trunks with artificially created snail scent trails rapidly decreased for 7 days, and the mortality was caused by P. manokwari predation. However, snails placed on tree trunks without snail scent trails were not attacked by P. manokwari. Therefore, P. manokwari climbed tree trunks, likely tracking the snail scent. We found that over 40\% of the snails placed on tree trunks with snail scent trails were eaten by P. manokwari within 7 days. This experiment supports the hypothesis that P. manokwari predation is an important cause of the rapid decline or extinction of native arboreal snails on Pacific islands.

}, doi = {10.1007/s10530-008-9287-1}, url = {http://www.springerlink.com/content/l654j1846k803u22/}, author = {Sugiura, S. and Yamaura, Y.} } @article {287, title = {Seasonal fluctuation of invasive flatworm predation pressure on land snails: Implications for the range expansion and impacts of invasive species}, journal = {Biological Conservation}, volume = {142}, number = {12}, year = {2009}, pages = {3013-3019}, chapter = {3013}, abstract = {

Introduction of the snail-eating flatworm Platydemus manokwari has caused extinction and decline of native land snails on tropical and subtropical islands. As the factors influencing flatworm predation pressure on land snails remain unclear, I examined the effects of seasonal variation in flatworm predation pressure on land snail survival in the wild on a subtropical island. I also examined the feeding activities of P. manokwari under laboratory conditions. Survival rates of land snails experimentally placed on the forest floor for 7 days ranged from 0\% to 100\% among seasons on the oceanic island Chichijima [Ogasawara (Bonin) Islands]. More than 90\% of snails were killed by P. manokwari within 7 days in the period from July to November, while less than 40\% of snails were killed in other months. Snail mortality rate (0\–100\%) attributable to P. manokwari was positively correlated with mean temperature (17.1\–27.3 \°C) in the study area. Laboratory experiments showed that low temperature influenced snail survival and regulated feeding activity of P. manokwari. Laboratory experiments also suggested that high densities of P. manokwari may cause a rapid decline in snail survival. Therefore, ambient temperature and density of P. manokwari may regulate seasonal variations in predation pressure on land snails. Recent global warming may increase the probability of invasion and population establishment, and elevate the impacts of P. manokwari in temperate regions.

}, doi = {10.1016/j.biocon.2009.07.032}, url = {http://www.sciencedirect.com/science/article/pii/S0006320709003619}, author = {Sugiura, S.} } @article {56, title = {Prey preference and gregarious attacks by the invasive flatworm Platydemus manokwari}, journal = {Biological Invasions}, volume = {12}, year = {2010}, month = {1507}, pages = {1499}, chapter = {1499}, abstract = {

The flatworm Platydemus manokwari (Tricladida: Rhynchodemidae) preys on various species of land snail, and its introduction to areas outside of its native range is thought to have caused the extinction of native land snails on several Pacific islands. Platydemus manokwari occurs in areas where land snails have been absent since its invasion, suggesting that the flatworm can prey on animals other than land snails. To identify the alternative prey and prey preferences of P. manokwari, I examined the feeding ecology of P. manokwari under field and laboratory conditions. Individuals were observed attacking live earthworms in a forest where land snails are already extinct, on Chichijima, Ogasawara (Bonin) Islands, Japan. I also observed them attacking earthworms and a species of isopod and land snail in the lab. To prey on the worm, similar to other earthworm-eating flatworms, P. manokwari wrapped itself around the prey and fed on it by inserting its pharynx into the earthworm\’s body. Large earthworms were able to escape P. manokwari attacks by autotomy, but the autotomized body parts were eaten. Several P. manokwari individuals together attacked earthworms that were larger than themselves. The laboratory experiments showed that such gregarious attacks increased predation success on both large earthworms and land snails. The flatworms also attacked the isopods, although the predation rate was low. These results demonstrate that P. manokwari is a polyphagous predator of slowmoving soil invertebrates (land snails, slugs, earthworms, and isopods) and that invasion by P. manokwari may directly and indirectly impact native soil fauna.

}, author = {Sugiura, S.} }