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PeerJ. 2017 Mar 2;5:e3011. doi: 10.7717/peerj.3011. eCollection 2017.

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

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Hakubi Center for Advanced Research, Kyoto University, Kyoto, Japan; Department of Zoology/Graduate School of Science, Kyoto University, Kyoto, Japan.



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.


To test this, I compared the morphology and behavior of two sympatric species of Taiwanese snail-eating snakes, Pareas atayal and P. formosensis.


Specimens collected in the same locality showed that the dentition asymmetry of P. formosensis was significantly smaller than that of P. atayal. Congruent to its weak asymmetry, P. formosensis showed a strong preference of slugs to snails in the feeding experiment.


The dietary specialization of P. formosensis on slugs would contribute to niche partitioning from the sympatric congener P. atayal. This study suggests that the diverse variation in the dentition asymmetry of pareid snakes is the result of their dietary specialization and divergence.


Adaptation; Evolutionary novelty; Left–right asymmetry; Predation; Specialization

Conflict of interest statement

The author declares there are no competing interests.

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