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Dramatic dietary shift maintains sequestered toxins in chemically defended snakes.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2020 Mar 17; Vol. 117 (11), pp. 5964-5969. Date of Electronic Publication: 2020 Feb 24. - Publication Year :
- 2020
-
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.<br />Competing Interests: The authors declare no competing interest.<br /> (Copyright © 2020 the Author(s). Published by PNAS.)
- Subjects :
- Animals
Anura
Bufanolides chemistry
Bufanolides isolation & purification
Bufonidae
Cardiac Glycosides
Colubridae
Defense Mechanisms
Glycosylation
Insecta
Larva
Molecular Weight
Oligochaeta
Stereoisomerism
Toxins, Biological isolation & purification
Biological Evolution
Diet
Feeding Behavior
Predatory Behavior
Snakes physiology
Toxins, Biological chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 1091-6490
- Volume :
- 117
- Issue :
- 11
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 32094167
- Full Text :
- https://doi.org/10.1073/pnas.1919065117