The Effects of Biting and Pulling on the Forces Generated during Feeding in the Komodo Dragon (Varanus komodoensis)

In addition to biting, it has been speculated that the forces resulting from pulling on food items may also contribute to feeding success in carnivorous vertebrates. We present an in vivo analysis of both bite and pulling forces in Varanus komodoensis, the Komodo dragon, to determine how they contribute to feeding behavior. Observations of cranial modeling and behavior suggest that V. komodoensis feeds using bite force supplemented by pulling in the caudal/ventrocaudal direction. We tested these observations using force gauges/transducers to measure biting and pulling forces. Maximum bite force correlates with both body mass and total body length, likely due to increased muscle mass. Individuals showed consistent behaviors when biting, including the typical medial-caudal head rotation. Pull force correlates best with total body length, longer limbs and larger postcranial motions. None of these forces correlated well with head dimensions. When pulling, V. komodoensis use neck and limb movements that are associated with increased caudal and ventral oriented force. Measured bite force in Varanus komodoensis is similar to several previous estimations based on 3D models, but is low for its body mass relative to other vertebrates. Pull force, especially in the ventrocaudal direction, would allow individuals to hunt and deflesh with high success without the need of strong jaw adductors. In future studies, pull forces need to be considered for a complete understanding of vertebrate carnivore feeding dynamics

Agricultural landscapes and the Loire River influence the genetic structure of the marbled newt in Western France

Abstract Amphibians are particularly sensitive to landscape fragmentation. Potential barriers between breeding sites can negatively influence the dispersal of individuals and increase genetic structure between populations. In this study, we genotyped 10 microsatellites for 334 marbled newts (Triturus marmoratus) at 11 different locations in Western France. Samples were collected in different regions with contrasting agricultural landscapes (low and high proportion of arable land in the north and south, respectively). We found a strong genetic structure between the northern and southern sampling sites. Isolation by distance was recorded after 62 km, but within the northern region, little or no genetic structure was detected over large distances (up to 114 km). Genetic structure at shorter distance (43 km) was found between sites situated in landscapes with larger amounts of arable lands. A significant positive relationship was found between the pairwise genetic distance (Fst) between sites and the amount of arable land together with the distance between sites. Our results suggest that the Loire River might act as a corridor for the marbled newt, while arable land might act as a barrier. Finally, although a large city is located between sampling sites, no effect was detected on population structure

Evolutionary Specialization of the Tongue in Vertebrates: Structure and Function

A conspicuous feature of extant tetrapods is a movable tongue that plays a role in food uptake, mastication, and swallowing. The tongue is a muscle mass covered by a mucosal sheath, but the tongues of amphibians, reptiles, birds, and mammals are diverse in general morphology and function. For example, in frogs and toads, a component of the musculus genioglossus serves as an intrinsic tongue muscle, with the anterior part of the tongue attached to the floor of the oral cavity. Nevertheless, these features of the tongue have allowed Anurans to diversify and disperse worldwide. On the other hand, the salamander tongue is connected to the oral cavity by a root with a cartilage or a bony skeleton, and it is mainly comprised of projection and retractor muscles. In this respect, the salamander tongue seems more similar to that of reptiles and mammals than to those of frogs and toads. The morphology and function of the tongues of some reptiles, such as chameleons, and some mammals, such as nectar-feeding bats, are examples of extreme specialization. Finally, the tongue has become almost vestigial in a few species of anurans, turtles, and birds. This review summarizes and discusses many specializations of tongue form and function among tetrapods