Biology Reference
In-Depth Information
3
A Summary of the Toxinology of
Duvernoy's Secretions: A Brief
Overview of the History of Colubrid
Oral Secretion Research
The formal scientific study of snake venoms has been a quiet but reasonably steady
endeavor since the mid-nineteenth century. Since the isolation of the presynaptic neuro-
toxin, crotoxin, from venom of the tropical rattlesnake (
Crotalus durissus terrificus
)
by Slotta and Fraenkel-Conrat in 1938, much has been learned about the composi-
tion of snake venoms. Venoms from advanced snakes such as viperids, elapids, and
atractaspidids have received consistent attention from toxinologists, separation scien-
tists (e.g., protein biochemists), pharmacologists, and other investigators. Oral secre-
tions from other colubroids have received far less comprehensive investigation. As
noted previously, many of these other species were artificially grouped together and
likely have a wide array of biologically active oral secretion components. An unknown
number of these snakes produce secretions or venoms/toxins of varying potency and
unknown potential medical importance. Some early authors considered the possibility
of “poisonings” inflicted by “harmless” snakes (Quelch, 1893). Scientific and medi-
cal interest in the potential toxicity of colubrid secretions and venoms dates from the
late nineteenth century (Mackessy, 2002; Weinstein and Kardong, 1994). When con-
sidering the effects of a “jubo” [a species of West Indian racer, probably the Cuban
racer,
Alsophis
(
Cubophis
Hedges et al., 2009)
cantherigerus
] perceived as nonven-
omous, the Cuban physician Don Felipe Poey commented on the ability of seem-
ingly harmless snakes suddenly to transform their “salivary glands” into “hazardous
glands” when sufficiently provoked (Poey, 1873). Some mid-nineteenth century natu-
ralists partitioned snakes into three classes:
Innocua
(considered “harmless”),
Suspecta
(not known to be venomous, but with “poisonous saliva” or with “slight” venomous
quality), and
Venenosa
(known to be venomous) (Nicholson, 1874). However, others
held the view that colubrid snakes collectively posed no threat. For example, Schlegel
(1828) concluded that as the structures of the “parotid gland” (Duvernoy's gland) of
colubrid snakes were similar to the structure of other salivary glands, and the bites of
any colubrid snake were not known at the time to be fatal to man, these snakes were
not truly venomous. This view persisted into the early twentieth century. Abercromby
(1910) stated “With the Opisthoglypha the removal of the fangs is unnecessary, as
their poison is so slight, and the grooved fangs, being at the back of the mouth, seldom
enter you when they bite.” This assertion did not prevent Martins (1916) from inves-
tigating the effects in animal models of Duvernoy's secretions from the Patagonian
racer (
Philodryas patagoniensis
). Beginning in the early twentieth century, several
