Meeting Abstract
Frogs are well known to catch prey by using a sticky tongue that can either be protruded over the tip of the jaw or in many species may be ballistically fired towards remote targets. Often frogs are generalist feeders and frog tongues stick to a vast diversity of different prey surfaces. Due to the rapidness of feeding in frogs, their tongues have to adhere instantaneously. Frog tongues are covered in mucus and the interaction of this mucus with the tongue and the prey surface will be critical for a successful feeding event. Thus, frog tongues provide an interesting example of a wet adhesive system that acts at high speeds on a variety of substrates. Here we measured the forces with that frogs of the South American genus Ceratophrys attach to glass. We recorded the forces during the impact and pulling phases of the feeding strike. We found that the maximum pulling forces were on average beyond the body weight of the animals. Further, pulling forces decreased over time while the frogs detached their tongues, which suggests a similar detachment mechanism like in so-called pressure sensitive adhesives (PSAs) that are of common technical use as adhesive tapes or labels. By using high speed videography, we were able to show fibrillation of the mucus during detachment. Further, we studied the comparative anatomy of frog tongues from the macroscopic to the microscopic level in nine different taxa, comprising species with protrusible and projectable tongues. For this we used a combined approach of micro-CT imaging and scanning electron microscopy. Among different frog taxa, we found a high degree of variation in tongue anatomy on all levels comprising the general shape, the internal anatomy, and the size, shape, and distribution of surface microstructures. The observed variation appears to be a mosaic of functional and phylogenetic patterns.
