Biology Reference
In-Depth Information
2
Differences Between Buccal Gland
Secretion and Associated Delivery
Systems of “True” Venomous
Snakes and “Colubrid” Snakes:
Low- Versus High-Pressure Gland
Function and Canaliculated Versus
Solid Dentition
A half-truth, like half a brick, is always more forcible as an argument than a whole
one. It carries better.
Stephen Leacock
2.1 Basic Considerations Regarding Gland Structure and
Function
The functional morphology of venom glands in “front-fanged” or “true” venomous
snakes (viperids, elapids, and atractaspidids) differs notably from the gland appara-
tus and associated dentition of other colubroids. An unknown number of these spe-
cies lack their homologous counterpart, the Duvernoy's gland (Kardong, 1996; Taub,
1966; Weinstein and Kardong, 1994; Weinstein et al., 2010; Zalisko and Kardong,
1992). Taub (1967) reported that about 17% (approximately 30 species) of colubrid
snakes studied (120 genera, 180 species) lacked evidence of Duvernoy's glands and,
in some discrete groups, as many as 90% examined lacked these glands.
Most Duvernoy's glands lack any significant storage capacity, exhibit a duct sys-
tem distinguishable from that of venom glands of front-fanged snakes, and usually
have no direct striated muscle insertion to pressurize the fundus of the gland. The
consequence is a low-pressure secretion-injecting system (Kardong, 1996; Kardong
and Lavin-Murcio, 1993; Taub, 1967; Weinstein and Kardong, 1994; Weinstein et al.,
2010).
Figure 2.1
(Panels A-C) illustrates the basic functional morphology of a typical
Duvernoy's gland with its limited muscle attachment and associated dentition. Some
members of the tribe, Dispholidini (Section 4.3), are exceptions to this, as they do
have some limited striated muscle attachment on the gland fundus and thereby have
