The nuchal gland system in Indonesian snakes: insights from function, structure, and evolution

概要

The nuchal glands are organs of chemical defense embedded under the skin of several
species of Rhabdophis and are known to contain toxins known as bufadienolides. The nuchal
gland system is integrated by toxin sequestration, specialized morphology, and specific
behavior. Snakes with the nuchal glands can consume toxic prey such as toads, sequester their
bufadienolides, and further utilize them to deter predators. Despite Indonesia's unique
environmental characteristics and its high level of biodiversity, the nuchal gland diversity of
natricine species in this region has been rarely investigated. The nuchal glands have been
already discovered in several Rhabdophis species of Indonesia, but there is no other detailed
information, particularly regarding the organ's structure, function, and evolution. Therefore, I
intend to investigate the nuchal gland system of snakes in Indonesia from the aspects of
antipredator behavior, chemical prey preference, structures, chemical composition, and
evolutionary history.
Materials and methods
I conducted the antipredator response experiment using artificial stimuli toward fortyeight individuals of R. subminiatus to investigate their antipredator behaviors, especially
nuchal glands-related behavior. Eight behavioral responses were recorded, and the correlation
of sex, body size, and body condition with these behaviors were analyzed. Chemical response
test was conducted on R. subminiatus to find out its prey selection and the possible source of
the toxins. Snakes were presented with prey chemical stimuli and their tongue flick frequency
was analyzed. ...