title: Asymmetry of mandibular dentition is associated with dietary specialization in snail-eating snakes.
abstract: BACKGROUND
  In 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.
  
  
  METHODS
  To test this, I compared the morphology and behavior of two sympatric species of Taiwanese snail-eating snakes,Pareas atayalandP. formosensis.
  
  
  RESULTS
  Specimens 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Hakubi Center for Advanced Research, Kyoto University, Kyoto, Japan; Department of Zoology/Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Hoso
keywords: Adaptation; Evolutionary novelty; Left–right asymmetry; Predation; Specialization