|Title:||Dramatic dietary shift maintains sequestered toxins in chemically defended snakes|
Savitzky, Alan H.
Silva, Anslem de
Nguyen, Tao Thien
|Author's alias:||吉田, 達哉|
|Publisher:||National Academy of Sciences|
|Journal title:||Proceedings of the National Academy of Sciences of the United States of America|
|Abstract:||Unlike other snakes, most species of Rhabdophis possess glands in their dorsal skin, sometimes limited to the neck, known as nucho-dorsal and nuchal glands, respectively. Those glands contain powerful cardiotonic steroids known as bufadienolides, which can be deployed as a defense against predators. Bufadienolides otherwise occur only in toads (Bufonidae) and some fireflies (Lampyrinae), which are known or believed to synthesize the toxins. The ancestral diet of Rhabdophis consists of anuran amphibians, and we have shown previously that the bufadienolide toxins of frog-eating species are sequestered from toads consumed as prey. However, one derived clade, the Rhabdophis nuchalis Group, has shifted its primary diet from frogs to earthworms. Here we confirm that the worm-eating snakes possess bufadienolides in their nucho-dorsal glands, although the worms themselves lack such toxins. In addition, we show that the bufadienolides of R. nuchalis Group species are obtained primarily from fireflies. Although few snakes feed on insects, we document through feeding experiments, chemosensory preference tests, and gut contents that lampyrine firefly larvae are regularly consumed by these snakes. Furthermore, members of the R. nuchalis Group contain compounds that resemble the distinctive bufadienolides of fireflies, but not those of toads, in stereochemistry, glycosylation, acetylation, and molecular weight. Thus, the evolutionary shift in primary prey among members of the R. nuchalis Group has been accompanied by a dramatic shift in the source of the species’ sequestered defensive toxins.|
|Description:||中国のヤマカガシは頸腺毒の成分をホタルから摂取していたことを発見 --ヒキガエルからホタルへとかけ離れた種間で毒源が移行した--. 京都大学プレスリリース. 2020-03-03.|
|Rights:||© 2020 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).|
|Appears in Collections:||Journal Articles|
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