Meeting Abstract
Among lizards, prey are captured with the tongue or the jaws. All iguanians are lingual feeders, and lingual feeding has evolved independently from jaw-feeding ancestors in several other squamate lineages. We compared the functional morphology of lingual feeding in the skink, Tiliqua scincoides, with several iguanians using high-speed videography, paraffin histology, and carbohydrate histochemistry. Each prey capture event involves tongue protrusion, tongue-prey contact, and tongue retraction. The proportion of each event devoted to contact and retraction is significantly longer in Tiliqua than in iguanians. Tongue-prey contact in Tiliqua also involved extensive foretongue spreading, greatly increasing contact area, whereas in iguanians, the contact area is typically minute. Preliminary phylogenetic PCA of tongue histological characters shows that Tiliqua groups with jaw-feeding scincid and lacertid taxa, not with iguanians. The iguanian tongue is covered with lingual glands, which are absent on the foretongue of Tiliqua and most other skinks. However, the sublingual glands in Tiliqua are hugely hypertrophied compared to iguanians and to a lesser extent, jaw-feeding skinks. All taxa secrete neutral mucins, but a preliminary analysis of AB-PAS staining intensity suggests that Tiliqua secretes more mucins per unit area than Sphenodon, iguanians, and jaw-feeding scincids and lacertids, suggesting greater viscosity and ‘stickiness’ of Tiliqua mucus, a hypothesis we are pursuing with materials testing. All data suggest that Tiliqua compensates for a weak adhesive mechanism compared to iguanians by secreting more, stickier mucus, increasing area of contact, and slowing retraction speed to prevent prey loss.
