The functional morphology of lingual prey capture in a scincid lizard, Tiliqua scincoides (Reptilia: Squamata)

Abstract

We investigated the functional morphology of lingual prey capture in the bluetongued 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. Highspeed 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.

A comparison of two techniques to identify the sex of the eastern blue‐tongue skink (Tiliqua scincoides scincoides)

“…The indoor skinks may have been exposed to a higher population density, and therefore increased mating‐induced male‐to‐male combat, and increased head size over generations 18, 19 . Certain food types given over generations can also impact the skinks head width and length due to their adaption to both lingual and jaw prey capture 20 . Low food availability due to inadequate care or high competition, predator awareness, and energy diversion to reaching sexual maturity over body growth has also been found to play a part in reduced growth rates, particularly in reduced snout‐vent lengths, in lizards 21–23 .…”

“…18,19 Certain food types given over generations can also impact the skinks head width and length due to their adaption to both lingual and jaw prey capture. 20 Low food availability due to inadequate care or high competition, predator awareness, and energy diversion to reaching sexual maturity over body growth has also been found to play a part in reduced growth rates, particularly in reduced snout-vent lengths, in lizards. [21][22][23] Juveniles in particular are susceptible to excessive energy expenditure and reduced growth rates from inadequate thermoregulatory zones, 24 particularly if they are not housed separately to adults, as they require different basking patterns.…”

Studies of the Behavioral Sequences: The Neuroethological Morphology Concept Crossing Ethology and Functional Morphology

“…Based on the investigation of behavioral sequences in numerous species, two modes of prey capture have been determined in squamates: (i) jaw grasping ( Figure 12 ), and (ii) lingual grasping ( Supplementary Material S6 ) with the dorsal or the ventral side of the tongue [ 67 , 68 , 69 , 70 , 71 , 72 ], independent of the trophic system morphology. Each prey/food capture demonstrates invariant MPs resulting from muscular activities and kinematics of coordinated gape and hyo-lingual cycles, regardless of the morphological traits and their individual plasticity (e.g., personality).…”

“…Each prey/food capture demonstrates invariant MPs resulting from muscular activities and kinematics of coordinated gape and hyo-lingual cycles, regardless of the morphological traits and their individual plasticity (e.g., personality). The proximal food sign stimulus acts on motor actions at two levels: (i) change in performance of the trophic system (capture mode), and (ii) modulation of trophic and post-cranial performance [ 71 , 72 , 73 , 74 ]. Three examples help to demonstrate the value of the neuroethological approach in understanding the evolution of prey capture in squamates.…”

“…In contrast, the capture behavior is more complex in the scincid Tiliqua scincoides that forage in various habitats including forests, grasslands, and human-altered habitats to find various food resources (e.g., plants, arthropods, snails, small vertebrates). This terrestrial species may use jaw or lingual prehension for different but also similar food items [ 71 ], and lingual protrusion may be modulated differently during lingual prehension [ 72 ]. This suggests an effect of proximal sign-stimulus on the MP of the tropic system at two levels: (i) change of the jaw-tongue control, (ii) modulation of the MP of the lingual muscular system.…”