Biology Reference
In-Depth Information
capture of mammalian prey versus the use of constriction by these snakes when captur-
ing lizards and frogs; Shine and Schwaner, 1985]. Shine and Schwaner (1985) even
noted that frequency of prey constriction among some Australian elapids was statis-
tically identical to that of some nonvenomous snakes. Therefore, the selective use
of venom may be an indicator of a prey-specific capture strategy possibly applied to
reduce the likelihood of reprisal from a more physically imposing prey item, while
constriction may be used to subdue prey that is more resistant to the subjugating effects
of a given venom.
In a rare study addressing the possible digestive function of Duvernoy's secre-
tions of a non-front-fanged colubroid, Rodriguez-Robles and Thomas (1992) assessed
the extent of digestion by
A. portoricensis
of a natural prey item,
Anolis cristatellus
(Puerto Rican crested anole) by comparing lizards recovered from the snakes' gas-
trointestinal (GI) tract 6 h after natural capture/deglutition, force-feeding of intact liz-
ards, or those with experimentally administered puncture wounds (by puncturing the
lizards with sterilized sewing needles). The force-feeding was conducted by shield-
ing the snakes' teeth in order to prevent accidental introduction of oral secretions, and
the artificially punctured anoles served to assess the possible role of puncture wounds
facilitating digestion by providing a pathway for the entrance of digestive enzymes
into the body cavity (Rodriguez-Robles and Thomas, 1992). The anoles were recov-
ered from the snakes' GI tract 6 h after natural deglutition or force-feeding, and a
qualitative scoring system was used to estimate the degree of digestion by examina-
tion of the condition of several body structures (“body wall,” forelimbs, etc.), and vis-
ceral organs (liver, lungs, etc.). The results were statistically analyzed, and the authors
reported that the general digestion of “envenomated” anoles was faster than those of
“nonenvenomated” anoles. In addition, digestive rates for several structures and vis-
ceral organs were faster in “envenomated” lizards in comparison with the “nonen-
venomated” group (Rodriguez-Robles and Thomas, 1992). The study had several
flaws that modify interpretation of the results. For example, the scoring system was
notably (but understandably) subjective; the induced artificial puncture wounds were
probably poor facsimiles of actual tooth-inflicted wounds, and as the experimental
groups of lizards were force-fed to the snakes, the possible role of cephalic-natural
olfactory stimulation of a prey item was probably absent. The last process could con-
ceivably play an important independent factor in the speed of digestion. However, in a
similarly uncommon study of nutrient signals that potentially stimulate digestion in a
henophidian, the Burmese python (
Python molurus
), Secor et al. (2002) reported that
neither cephalic, gastric, or intestinal (physical) signals, nor the luminal presence of
bile, lipids, or glucose, induced an intestinal response. Rather, a combination of nutri-
ents, especially amino acids and peptides (also, provision of a homogenized rat mix-
ture) induced an intestinal response resembling that after ingestion of intact rodent
prey (Secor et al., 2002). Secor et al. (2002) emphasized the carnivorous diet per inges-
tion of large whole prey items by
Python molurus
, thus the natural gastric response
to a rich proteinaceous bolus. Therefore, the experiments of Rodriguez-Robles and
Thomas (1992) may have produced a digestive response, as they did introduce a natu-
ral prey item to the snakes' digestive tracts. The relatively high proteolytic activities of
A. portoricensis
Duvernoy's secretion (Weldon and Mackessy, 2010) could be viewed
