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We investigated the functional morphology of lingual prey capture in the blue-tongued skink, Tiliqua scincoides, a lingual-feeding lizard nested deep within the family Scincidae, which is presumed to be dominated by jaw-feeding. We used kinematic analysis of high-speed video to characterize jaw and tongue movements during prey capture. Phylogenetically informed principal components analysis of tongue morphology showed that, compared to jaw-feeding scincids and lacertids, T. scincoides and another tongue-feeding scincid, Corucia zebrata, are distinct in ways suggesting an enhanced ability for hydrostatic shape change. Lingual feeding kinematics show substantial quantitative and qualitative variation among T. scincoides individuals. High-speed video analysis showed that T. scincoides uses significant hydrostatic elongation and deformation during protrusion, tongue-prey contact, and retraction. A key feature of lingual prey capture in T. scincoides is extensive hydrostatic deformation to increase the area of tongue-prey contact, presumably to maximize wet adhesion of the prey item. Adhesion is mechanically reinforced during tongue retraction through formation of a distinctive "saddle" in the foretongue that supports the prey item, reducing the risk of prey loss during retraction., (© 2020 Wiley Periodicals LLC.)

Vomeronasal chemoreception, an important chemical sense in squamate reptiles (lizards and snakes), is mediated by paired vomeronasal organs (VNOs), which are only accessible via ducts opening through the palate anteriorly. We comparatively examined the morphology of the oral cavity in lizards with unforked tongues to elucidate the mechanism of stage I delivery (transport of chemical-laden fluid from the tongue tips to the VNO fenestrae) and to test the generality of the Gillingham and Clark (1981. Can J Zool 59:1651-1657) hypothesis (based on derived snakes), which suggests that the sublingual plicae act as the direct conveyors of chemicals to the VNOs. At rest, the foretongue lies within a chamber formed by the sublingual plicae ventrally and the palate dorsally, with little or no space around the anterior foretongue when the mouth is closed. There is a remarkable conformity between the shape of this chamber and the shape of the foretongue. We propose a hydraulic mechanism for stage I chemical transport in squamates: during mouth closure, the compliant tongue is compressed within this cavity and the floor of the mouth is elevated, expressing fluid from the sublingual glands within the plicae. Chemical-laden fluid covering the tongue tips is forced dorsally and posteriorly toward the VNO fenestrae. In effect, the tongue acts as a piston, pressurizing the fluid surrounding the foretongue so that chemical transport to the VNO ducts is effected almost instantaneously. Our findings falsify the Gillingham and Clark (1981. Can J Zool 59:1651-1657) hypothesis for lizards lacking forked, retractile tongues., (2008 Wiley-Liss, Inc)

Horned lizards (Iguanidae, Phrynosomatinae, Phrynosoma) are morphologically specialized reptiles characterized by squat, tank-like bodies, short limbs, blunt snouts, spines and cranial horns, among other traits. They are unusual among lizards in the degree to which they specialize on a diet of ants, but exceptional in the number of pugnacious, highly venomous, stinging ants they consume, especially harvester ants (genus Pogonomyrmex). Like other iguanian lizards, they capture insect prey on the tongue, but unlike other lizards, they neither bite nor chew dangerous prey before swallowing. Instead, they employ a unique kinematic pattern in which prey capture, transport and swallowing are combined. Nevertheless, horned lizards consume dozens of harvester ants without harm. We show that their derived feeding kinematics are associated with unique, mucus-secreting pharyngeal papillae that apparently serve to immobilize and incapacitate dangerous ants as they are swallowed by compacting them and binding them in mucus strands. Radially branched esophageal folds provide additional mucus-secreting surfaces the ants pass through as they are swallowed. Ants extracted from fresh-killed horned lizard stomachs are curled ventrally into balls and bound in mucus. We conclude that the pharyngeal papillae, in association with a unique form of hyolingual prey transport and swallowing, are horned lizard adaptations related to a diet of dangerous prey. Harvester ant defensive weapons, along with horned lizard adaptations against such weapons, suggest a long-term, predator-prey, co-evolutionary arms race between Phrynosoma and Pogonomyrmex., (Copyright 2008 Wiley-Liss, Inc.)

The structure of communities may be largely a result of evolutionary changes that occurred many millions of years ago. We explore the historical ecology of squamates (lizards and snakes), identify historically derived differences among clades, and examine how this history has affected present-day squamate assemblages globally. A dietary shift occurred in the evolutionary history of squamates. Iguanian diets contain large proportions of ants, other hymenopterans, and beetles, whereas these are minor prey in scleroglossan lizards. A preponderance of termites, grasshoppers, spiders, and insect larvae in their diets suggests that scleroglossan lizards harvest higher energy prey or avoid prey containing noxious chemicals. The success of this dietary shift is suggested by dominance of scleroglossans in lizard assemblages throughout the world. One scleroglossan clade, Autarchoglossa, combined an advanced vomeronasal chemosensory system with jaw prehension and increased activity levels. We suggest these traits provided them a competitive advantage during the day in terrestrial habitats. Iguanians and gekkotans shifted to elevated microhabitats historically, and gekkotans shifted activity to nighttime. These historically derived niche differences are apparent in extant lizard assemblages and account for some observed structure. These patterns occur in a variety of habitats at both regional and local levels throughout the world.

An incipient form of tongue projection occurs in Phrynocephalus helioscopus, a generalized agamid lizard. We argue that this condition represents a functional intermediate between typical lingual prehension and chamaeleontid tongue projection, and that tongue projection evolved in chameleons by augmentation of ancestral mechanisms still operating in related, generalized lizards.

A number of studies have focused on the form and function of intracranial movements in lizards (cranial kinesis), but rarely has the anatomy and potential movement of individual joints been evaluated. Frazetta (1983) suggested that cranial kinesis is an adaptation for precise and simultaneous contact of upper and lower jaws during prey capture. According to Schwenk (2000), cranial kinesis should therefore be restricted to lizards employing jaw-prehension (Scleroglossa) and absent in lingual feeders (Iguania). Limited functional observations are consistent with this hypothesis. We studied the microscopic anatomy of the kinetic joints in iguanian and scleroglossan lizards and found that all five intracranial joints we examined were capable of movement in scleroglossan lizards, but only two of five joints showed potential for kinesis in iguanian species. Although more species need to be sampled, these data offer preliminary support to the Frazzetta and Schwenk hypotheses.

Sexual selection operates by acting on variation in mating success. However, since selection acts on whole-organism manifestations (i.e., performance) of underlying morphological traits, tests for phenotypic effects of sexual selection should consider whole-animal performance as a substrate for sexual selection. Previous studies have revealed positive relationships between performance and survival, that is, natural selection, but none have explicitly tested whether performance may influence reproductive success (through more matings), that is, sexual selection. Performance predicts dominance in some species, implying the effects of sexual selection, but how it does so has not been established, nor is it certain whether performance might be a by-product of selection for something else, for example, elevated circulating testosterone levels. We investigated the potential for sexual selection on sprint speed performance in collared lizards (Crotaphytus collaris), considering the potential mediating effects of circulating hormone levels. Among territorial, adult male collared lizards, only sprint speed significantly predicted territory area and number of offspring sired as determined by genetic paternity analysis. Body size, head size, and hind limb length had no effect. Neither plasma testosterone levels nor corticosterone levels correlated with sprint speed, territory area, or number of offspring sired. Thus, our results provide a direct link between whole-animal performance and reproductive success, suggesting that intrasexual selection can act directly on sprint speed performance and drive the evolution of underlying morphological traits. [ABSTRACT FROM AUTHOR]

Viviparity (live bearing) has evolved from egg laying (oviparity) in many lineages of lizards and snakes, apparently in response to occupancy of cold climates. Explanations for this pattern have focused on the idea that behaviorally thermoregulating (sun-basking) pregnant female reptiles can maintain higher incubation temperatures for their embryos than would be available in nests under the soil surface. This is certainly true at very high elevations, where only viviparous species occur. However, comparisons of nest and lizard temperatures at sites close to the upper elevational limit for oviparous reptiles (presumably, the selective environment where the transition from oviparity to viviparity actually occurs) suggest that reproductive mode has less effect on mean incubation temperatures than on the diel distribution of those temperatures. Nests of the oviparous scincid lizard Bassiana duperreyi showed smooth diel cycles of heating and cooling. In contrast, body temperatures of the viviparous scincid Eulamprus heatwolei rose abruptly in the morning, were high and stable during daylight hours, and fell abruptly at night. Laboratory incubation experiments mimicking these patterns showed that developmental rates of eggs and phenotypic traits of hatchling B. duperreyi were sensitive to this type of thermal variance as well as to mean temperature. Hence, diel distributions as well as mean incubation temperatures may have played an important role in the selective forces for viviparity. More generally, variances as well as mean values of abiotic factors may constitute significant selective forces on life-history evolution. [ABSTRACT FROM AUTHOR]