, Volume 22, Issue 3, pp 187-198

First online:

Nuchal glands: a novel defensive system in snakes

  • Akira MoriAffiliated withDepartment of Zoology, Graduate School of Science, Kyoto University Email author 
  • , Gordon M. BurghardtAffiliated withDepartments of Psychology and Ecology and Evolutionary Biology, University of Tennessee
  • , Alan H. SavitzkyAffiliated withDepartment of Biological Sciences, Old Dominion University
  • , Kathleen A. RobertsAffiliated withDepartment of Biological Sciences, Old Dominion UniversityDepartment of Natural Resources and Environmental Sciences, Alabama A & M University
  • , Deborah A. HutchinsonAffiliated withDepartment of Biological Sciences, Old Dominion UniversityDepartment of Biology, Coastal Carolina University
  • , Richard C. GorisAffiliated with

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Of the various chemical defensive adaptations of vertebrates, nuchal glands are among the most unusual. First described in a Japanese natricine snake, Rhabdophis tigrinus, in 1935, these organs are embedded under the skin of the neck region as a series of paired glands that have neither lumina nor ducts. The major chemical components of the glandular fluid are bufadienolides, which are cardiotonic steroids also found in the skin secretion of toads. Here we review early studies of nuchal glands and briefly introduce our recent findings on the sequestration of bufadienolides from consumed toads and the maternal provisioning of those sequestered compounds. We summarize behavioral studies associated with the antipredator function of the nuchal glands, which have been conducted during our more than decade-long collaboration. Results of preliminary analyses on the possible costs of toad-eating and on the ultrastructure of the nuchal glands are also presented. Finally, we discuss the evolutionary origin of the nuchal glands and suggest future directions designed to understand the biological importance of these novel vertebrate organs, which have evolved in a limited number of snake species.


Rhabdophis tigrinus Bufo Dietary sequestration Antipredator behavior Bufadienolide Natricine snakes