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activities, and low levels of acetylcholinesterase and phosphodiesterase. They also
detected the rapid hydrolysis of the α-subunit of human fibrinogen by the whole
“venom” (secretion). Polyacrylamide gel electrophoresis revealed about 22 bands
with most molecular masses ranging between 25 and 62 kDa, but mass spectroscopy
resolved a complex group of proteins in the 1.5-13 kDa range, and low intensity sig-
nals in the 6.2-8.8 kDa range may have represented the presence of three-finger-fold
toxins (Weldon and Mackessy, 2010). A 25-kDa peptide was found to have sequence
homology with tigrin, the CRISP from venom of
R. tigrinus
. The “venom” had higher
lethal potency for mice (2.1 μg/g) than for the American or green anole,
Anolis caro-
linensis
(3.8 μg/g; Weldon and Mackessy, 2010). Intradermal injection of 1.0 μg or
5.0 μg of crude secretion caused hemorrhage in mice, and a dose-related magnitude
of induced hemorrhage was noted. Mice and anoles included in the lethal potency
determinations reportedly exhibited extensive pulmonary hemorrhage (Weldon and
Mackessy, 2010). These investigators speculated that the
in vitro
fibrinogenase activ-
ity may account for reports of prolonged bleeding (“
…
by disrupting the blood clot
cascade and inducing hypofibrinogenemia
…
”) in cases of bites from these and other
non-front-fanged colubroids (e.g.,
Philodryas
spp.). They also hypothesized a role for
the multiple proteinases/hemorrhagins present in this secretion in the local effects of
bites from this species (Weldon and Mackessy, 2010).
4.2.6.3 Should
Alsophis portoricensis
Duvernoy's Secretion Be Called
“Venom”?
Unlike most other species of non-front-fanged colubroids, the possible biological
functions of
A. portoricensis
Duvernoy's secretions have been investigated by both
laboratory study and field observations. Several investigators have described the pref-
erential engagement of the enlarged posterior maxillary teeth in response to strug-
gling movements of seized anoline prey (Rodriguez-Robles, 1992; Rodriguez-Robles
and Thomas, 1992; Thomas and Prieto-Hernandez, 1985). Rodriguez-Robles (1992)
described the specific response of
A. portoricensis
specimens to anoles attempting
to escape the snake's grasp. He reported that anoles were always held following suc-
cessful strikes, and if the grasped lizard struggled after capture, the snakes “chewed”
in order to embed the posterior maxillary teeth. Vigorously struggling prey was held
firmly, and forceful “chewing” ensued until the lizard was still. The jaw movements
did not seem to facilitate swallowing as the snake did not reposition the grasped prey,
and therefore were considered to be a possible means to introduce “venom” into the
prey (Rodriguez-Robles, 1992). This suggests active use of these secretions in either
prey subjugation or tranquilization. Interestingly, Rodriguez-Robles (1992) also
reported personal and communicated observations of
A. portoricensis
accomplishing
prey [laboratory mice and a teiid lizard,
Ameiva exsul
(Puerto Rican ground lizard)]
capture/restraint with constriction alone. As noted by Rodriguez-Robles (1992), prey
subjugation strategies using constriction or oral secretions are not mutually exclusive
and have precedent in some Australian elapids [e.g., the apparently preferential use of
venom by some tiger snakes (
Notechis
spp.) and brown snakes (
Pseudonaja
spp.) in
