Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation

BackgroundCrocodilians have dominated predatory niches at the water-land interface for over 85 million years. Like their ancestors, living species show substantial variation in their jaw proportions, dental form and body size. These differences are often assumed to reflect anatomical specialization related to feeding and niche occupation, but quantified data are scant. How these factors relate to biomechanical performance during feeding and their relevance to crocodilian evolutionary success are not known.Methodology/Principal FindingsWe measured adult bite forces and tooth pressures in all 23 extant crocodilian species and analyzed the results in ecological and phylogenetic contexts. We demonstrate that these reptiles generate the highest bite forces and tooth pressures known for any living animals. Bite forces strongly correlate with body size, and size changes are a major mechanism of feeding evolution in this group. Jaw shape demonstrates surprisingly little correlation to bite force and pressures. Bite forces can now be predicted in fossil crocodilians using the regression equations generated in this research.Conclusions/SignificanceCritical to crocodilian long-term success was the evolution of a high bite-force generating musculo-skeletal architecture. Once achieved, the relative force capacities of this system went essentially unmodified throughout subsequent diversification. Rampant changes in body size and concurrent changes in bite force served as a mechanism to allow access to differing prey types and sizes. Further access to the diversity of near-shore prey was gained primarily through changes in tooth pressure via the evolution of dental form and distributions of the teeth within the jaws. Rostral proportions changed substantially throughout crocodilian evolution, but not in correspondence with bite forces. The biomechanical and ecological ramifications of such changes need further examination

The neurogenic bladder: medical treatment

Neurogenic bladder sphincter dysfunction (NBSD) can cause severe and irreversible renal damage and bladder-wall destruction years before incontinence becomes an issue. Therefore, the first step in adequate management is to recognize early the bladder at risk for upper- and lower-tract deterioration and to start adequate medical treatment proactively. Clean intermittent catheterization combined with anticholinergics (oral or intravesical) is the standard therapy for NBSD. Early institution of such treatment can prevent both renal damage and secondary bladder-wall changes, thereby potentially improving long-term outcomes. In children with severe side effects or with insufficient suppression of detrusor overactivity despite maximal dosage of oral oxybutynin, intravesical instillation is an effective alternative. Intravesical instillation eliminates systemic side effects by reducing the first-pass metabolism and, compared with oral oxybutynin, intravesical oxybutynin is a more potent and long-acting detrusor suppressor. There is growing evidence that with early adequate treatment, kidneys are saved and normal bladder growth can be achieved in children so they will no longer need surgical bladder augmentation to achieve safe urinary continence in adolescence and adulthood