Jayne Bruce C, Bamberger Abigail L, Mader Douglas R, Bartoszek Ian A
Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA.
Tropical Veterinary Services, Big Pine Key, FL 33043, USA.
Integr Org Biol. 2022 Aug 25;4(1):obac033. doi: 10.1093/iob/obac033. eCollection 2022.
Snakes are a phylogenetically diverse (> 3500 species) clade of gape-limited predators that consume diverse prey and have considerable ontogenetic and interspecific variation in size, but empirical data on maximal gape are very limited. To test how overall size predicts gape, we quantified the scaling relationships between maximal gape, overall size, and several cranial dimensions for a wide range of sizes (mass 8-64,100 g) for two large, invasive snake species: Burmese pythons () and brown treesnakes (). Although skull size scaled with negative allometry relative to overall size, isometry and positive allometry commonly occurred for other measurements. For similar snout-vent lengths (SVL), the maximal gape areas of Burmese pythons were approximately 4-6 times greater than those of brown treesnakes, mainly as a result of having a significantly larger relative contribution to gape by the intermandibular soft tissues (43% vs. 17%). In both snake species and for all types of prey, the scaling relationships predicted that relative prey mass (RPM) at maximal gape decreased precipitously with increased overall snake size. For a given SVL or mass, the predicted maximal values of RPM of the Burmese pythons exceeded those of brown treesnakes for all prey types, and predicted values of RPM were usually least for chickens, greatest for limbed reptiles and intermediate for mammals. The pythons we studied are noteworthy for having large overall size and gape that is large even after correcting for overall size, both of which could facilitate some large individuals (SVL = 5 m) exploiting very large vertebrate prey (e.g., deer > 50 kg). Although brown treesnakes had longer quadrate bones, Burmese pythons had larger absolute and larger relative gape as a combined result of larger overall size, larger relative head size, and most importantly, greater stretch of the soft tissues.
蛇是一个系统发育上具有多样性（超过3500种）的口裂受限捕食者类群，它们捕食种类繁多的猎物，并且在体型上有显著的个体发育和种间差异，但关于最大口裂的实证数据非常有限。为了测试整体体型如何预测口裂，我们针对两种大型入侵蛇类：缅甸蟒（Python bivittatus）和棕树蛇（Boiga irregularis），在广泛的体型范围（体重8 - 64100克）内，量化了最大口裂、整体体型以及几个颅骨尺寸之间的缩放关系。尽管相对于整体体型，头骨大小呈负异速生长缩放，但其他测量通常呈现等速生长和正异速生长。对于相似的吻肛长度（SVL），缅甸蟒的最大口裂面积大约是棕树蛇的4 - 6倍，这主要是因为下颌间软组织对口裂的相对贡献显著更大（43%对17%）。在这两种蛇类以及所有类型的猎物中，缩放关系预测，最大口裂时的相对猎物质量（RPM）会随着蛇整体体型的增加而急剧下降。对于给定的SVL或体重，缅甸蟒在所有猎物类型下的RPM预测最大值都超过棕树蛇，并且RPM的预测值通常对鸡类最小，对有肢爬行动物最大，对哺乳动物则居中。我们研究的蟒蛇因其整体体型大且即使校正整体体型后口裂仍很大而值得注意，这两者都有助于一些大型个体（SVL = 5米）捕食非常大的脊椎动物猎物（例如，体重超过五十千克的鹿）。尽管棕树蛇的方骨更长，但缅甸蟒由于整体体型更大、相对头部尺寸更大，以及最重要的是软组织伸展更大，所以具有更大的绝对口裂和相对口裂。
