Snails can survive passage through a bird’s digestive system

Abstract

Aim Predation is generally viewed as a factor that limits the distribution of animal prey species. However, in certain instances, such as seed dispersal, predation may enhance the dispersal capability of prey species. In a prior study, we found that land snails are preyed upon by the Japanese white-eye (Zosterops japonicus) and the brown-eared bulbul (Hypsipetes amaurotis) in the Ogasawara Islands. In this paper we provide experimental and field evidence indicating that land snails could potentially be dispersed through bird predation.Location Hahajima Island of the Ogasawara Islands in the western Pacific.Methods Experimentation was first performed to test whether the land snail Tornatellides boeningi could remain alive after being swallowed and passed through the bird digestive system. Next, in order to investigate the potential role of internal bird transport and dispersal of this snail, we investigated the relationship between the distribution of population genetic diversity in the snail and the regional geographical abundance of predatory birds. The population genetic structure of T. boeningi and isolation by distance were inferred with Arlequin. The association between nucleotide diversity in T. boeningi populations and population density of predators was examined using a generalized linear mixed model. We conducted a likelihood ratio test for the full model and for another model that removed the fixed effect. ResultsOf the 119 snails fed to Japanese white-eyes and 55 snails fed to browneared bulbuls, 14.3% and 16.4% of the snails, respectively, passed through the gut alive. Additionally, one snail gave birth to juveniles after emerging from a bird's gut. Significant heterogeneity among the populations of T. boeningi on Hahajima was indicated using AMOVA; however, there was no evidence of isolation by distance. A positive correlation was found between levels of mitochondrial DNA variation among and within T. boeningi populations and the density of Japanese white-eyes in the wild.Main conclusions Bird predation appears to be a method of dispersal for T. boeningi, and our results suggest that bird-mediated dispersal plays a role in land snail population structure.

Successful escape of bombardier beetles from predator digestive systems

“…Successful escape from predators' digestive systems has been reported in several animal species: a blind snake from a toad [13], adult diving beetles from a toad [14], a carabid beetle larva from a toad [15], horsehair worms from fishes and frogs [8] and land snails from birds [16]. However, the ecological factors determining successful escape remain unexplored.…”

How did this snail get here? Several dispersal vectors inferred for an aquatic invasive species

“…Whereas external attachment and dispersal of eggs and ⁄ or adults is the most probable mode of transport (Malone, 1965b), egg capsules of Physa anatina Lea, 1864 might also be transported in the digestive system or the crop of killdeer (Charadrius vociferous Linnaeus, 1758) and mallards (Anas platyrhynchos Linnaeus, 1758) (Malone, 1965b). More recently, successful internal transport potential has been found for whole snails (Cadée, 2011;Gittenberger, 2012;Van Leeuwen et al, 2012b;Wada, Kawakami & Chiba, 2012), although not for Physa. Dispersal by waterbirds between rice fields and the park, whether internal or external, may be sufficient to explain genetic similarity at this large spatial scale.…”

“…To test the potential for this mode of dispersal in our system, we divided the ponds in the park into groups with either high or low mammalian visitation rates. If large mammals indeed disperse snails, the more frequent exchange of snails between ponds visited by mammals would reduce genetic differentiation between these populations (Mader, van Vierssen & Schwenk, 1998;Wada et al, 2012).…”

Unravelling the riddle of Radix: DNA barcoding for species identification of freshwater snail intermediate hosts of zoonotic digeneans and estimating their inter-population evolutionary relationships

“…The Hampshire locality is a feeding site for migratory birds, particularly those from mainland Europe. Considerable evidence exists that birds traffic snail eggs and juveniles on feathers and feet (Figuerola et al, 2005); snails might also survive passage through bird digestive systems (Wada et al, 2012). Such translocation could account for some of the relations between UK specific populations of R. auricularia and also those of other populations within the European clade.…”