Asymmetry of mandibular dentition is associated with dietary specialization in snail-eating snakes

Abstract

BackgroundIn vertebrates, the left-and-right pairs of homologous organs are generally present in equal numbers. A remarkable exception is snail-eating snakes in the family Pareidae: almost all the pareid snakes have much more teeth on the right mandible than on the left for functional specialization in feeding on the dextral majority of land snails. Because the only exceptional species with symmetric dentition has been regarded as a slug-eater, the extent of dietary specialization on slugs could shape the degree of the lateral asymmetry of mandibular dentition (dentition asymmetry) even among snail eaters.MethodsTo test this, I compared the morphology and behavior of two sympatric species of Taiwanese snail-eating snakes,Pareas atayalandP. formosensis.ResultsSpecimens collected in the same locality showed that the dentition asymmetry ofP. formosensiswas significantly smaller than that ofP. atayal. Congruent to its weak asymmetry,P. formosensisshowed a strong preference of slugs to snails in the feeding experiment.DiscussionThe dietary specialization ofP. formosensison slugs would contribute to niche partitioning from the sympatric congenerP. atayal. This study suggests that the diverse variation in the dentition asymmetry of pareid snakes is the result of their dietary specialization and divergence.