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and was swallowed by the snake in approximately 10 min (Pineda Lizano, 2010). A
Central American cat-eyed snake (
Leptodeira septentrionalis polysticta
) immobilized
a Mexican blue-spotted treefrog (
Smilisca cyanosticta
) by “chewing” the frog's hind-
leg “until the rear fangs were engaged” (Hernández-Ríos et al., 2011). Three minutes
after being seized by the snake, the frog's movements ceased, and it was swallowed
(Hernández-Ríos et al., 2011). Differences in observations of natural prey handling
may be related to the prey specificity of toxins present in Duvernoy's secretions or
venoms, and/or the individual prey-specific capture strategy, as well as the successful
introduction of Duvernoy's secretions into the seized prey. In comparison with their
lethal potency for mice, Duvernoy's secretions from
B. irregularis
had markedly higher
toxicity for scincid and gekkonid lizards as well as domestic chickens, suggesting prey
specificity of these secretions (Mackessy et al., 2006). As noted above, the presence of
prey-specific toxins in oral secretions of these snakes has been established by the char-
acterization of saurian and avian-specific neurotoxins from Duvernoy's secretions of
B. dendrophila
and
B. irregularis
(Pawlak et al., 2006, 2009). Thus, as evidence of
active biological use of Duvernoy's secretions in prey subjugation is accumulated, com-
bined with verified toxicity in various natural prey species, some of these secretions will
accommodate the current defining criteria for “venom” and will likely be so classified.
2
The similarity of chromatographic and antigenic complexity of venoms from
viperids, elapids, and the Duvernoy's secretions from other colubroids has been noted
by investigators (Fry et al., 2003; Mackessy, 2002; Weinstein and Smith, 1993).
Characterization of a Duvernoy's gland transcriptome from
P. olfersii
revealed venom
constituents and complexity similar to that of viperids (Ching et al., 2006). An ear-
lier genomic analysis reported toxin classes common to many venomous front-fanged
colubroid taxa present among the non-front-fanged colubroids examined (Fry et al.,
2003). Transcriptomic and proteomic analysis of Duvernoy's secretion (“venom”) of
the dog-faced water snake (
Cerberus rhynchops
) characterized a new group of pro-
teins, the “ryncolins” (the proposed protein family was named “veficolins,” for “venom
ficolins”; OmPraba et al., 2010). These proteins showed sequence homology with fico-
lin, a mammalian protein with collagen-like and fibrinogen-like domains, prompting
speculation that ryncolins might induce platelet aggregation and/or initiate comple-
ment activation (OmPraba et al., 2010). A recent comparative evaluation of Duvernoy's
gland (“venom gland”) morphology and transcriptomes of representative colubroid
genera supported the concept of shared toxin classes among many genera of advanced
snakes, including former colubrid genera, viperids, and elapids (Fry et al., 2008).
Continuing analysis of Duvernoy's secretions and venoms from these diverse
snake species may identify a pool of biomedically useful components. The charac-
terization of these may provide tools useful in laboratory medicine (especially in
blood coagulation studies), and possibly, pharmacotherapeutics. Such investigations
may also clarify some of the medical effects observed after bites inflicted by some of
these non-front-fanged colubroid species.
2
To date, expert consensus defines venom as a toxic substance produced in a highly developed secretory
organ or group of cells that is delivered by the act of biting or stinging, typically via a specialized appara-
tus. These substances are deleterious to other organisms at a certain dosage and are actively used in prey
acquisition and/or defense (Mebs, 1978, 2002; Minton, 1974; Minton and Minton, 1980; Russell, 1980).
