The vomeronasal organ of the skink, Scincella lateralis: the morphology and role in predation

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Virginia Polytechnic Institute and State University

A qualitative and quantitative comparison of the vomeronasal organ was made of the autarchoglossan lizards: Scincella lateralis, Eumeces fasciatus, Eumeces inexpectatus, and Ophisaurus ventralis, and the ascalobotans: Sceloporus undulatus, Hemidactylus turcicus, and Xantusia vigilis. As judged by the thickness of the vomeronasal sensory epithilium the vomeronasal organ was most highly developed in Ophisaurus venteralis and least developed in Sceloporus undulatus.

A comparison of the relationship between the vomeronasal sensory epithelium thickness and vomeronasal capsule length of autarchoglossans and ascalobotans supports the hypothesis that the vomeronasal organs of of autarchoglossans are larger than ascalobotans. However, a comparison of mean residuals for the species utilized in this study indicate that the relative size of the vomeronasal organ may be related to ecology as well as systematic relationships. Lizards that are secretive, fossorial, nocturnal or crepuscular have a tendency to have relatively well developed vomeronasal organs as measured by the thickness of the vomeronasal sensory epithelium, and lizards that are diurnal, visually oriented, and aboreal generally have smaller, less developed vomeronasal organs.

Scincella lateralis responds to both visual and chemical cues of prey. A visual stimulus is associated with an increased rate of tongue flicking, orientation to the prey, and attack behavior. Chemical cues are unimportant when the visual cue (movement) is present. When prey are non-moving or dead, chemical cues enable the lizard to distinguish potential prey from inanimate objects.

Vision and the chemical senses interact in a complex way to form the predatory repertoire of Scincella lateralis. Lizards may adopt one of two basic foraging strategies; an active foraging strategy or a sit-and-wait strategy. Lizards in the active foraging mode use both visual and chemical cues to detect moving or non-moving prey. A lizard in the sit-and-wait mode uses vison to detect prey movement. However, if the prey eludes capture after a lizard in the sit-and-wait mode begins its predatory attack, chemical cues may be used to track or identify the prey.