Bite strength

Abstract: Summary 1The theory of the evolution of secondary sexual traits through male–male competition is based on the assumption that these traits are reliable cues for an animal's fighting capacity. In this paper, we test whether a secondary sexual trait, dewlap size, is an honest predictor of bite strength in Anolis lizards. Since male anoles will bite one another during territorial fights, bite performance may play an important role in determining the outcome of male–male fights. 2We measured dewlap size and bite force in a size series of adult males of three Jamaican anoles, i.e. Anolis grahami Gray 1845, A. lineatopus Gray 1840 and A. valencienni Dumeril & Bibron 1837. 3In both A. grahami and A. lineatopus, males with relatively large dewlaps tend to bite relatively harder, while the relationship between relative dewlap size and bite force was clearly non-significant within the twig anole A. valencienni. 4Our results thus suggest that dewlap size is an indicator of relative bite force in the former two species, but not in the latter. We argue that interspecific variation in territorial behaviour might explain this difference.

Abstract: Within populations, individual animals may vary considerably in morphology and ecology The degree to which variation in morphology is related to ecological variation within a population remains largely unexplored We investigated whether variation in body size and shape among sexes and age classes of the lizard Podarcis melisellensis translates in differential whole-animal performance (sprint speed, bite force), escape and prey attack behaviour in the field, microhabitat use and diet Male and female adult lizards differed significantly in body size and head and limb proportions These morphological differences were reflected in differences in bite strength, but not in sprint speed Accordingly, field measurements of escape behaviour and prey attack speed did not differ between the sexes, but males ate larger, harder and faster prey than females In addition to differences in body size, juveniles diverged from adults in relative limb and head dimensions These shape differences may explain the relatively high sprint and bite capacities of juvenile lizards Ontogenetic variation in morphology and performance is strongly reflected in the behaviour and ecology in the field, with juveniles differing from adults in aspects of their microhabitat use, escape behaviour and diet © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 251-264

Abstract: Objective: The aim of the present study was to investigate whether the maximum bite force (MBF) can be improved by the replacement of complete dentures for elderly people. Design: Nine edentulous volunteers, mean age 74.2 (± 5.5) years and average denture experience 19.4 ± 19.5 years (1 to 50 years) had replacement dentures made. After a rehearsal session, MBF was recorded with the old dentures, and with the new dentures immediately at insertion, at 3, 8 days, 2–3 weeks, 1, 2, 3 and 6–10 months post insertion (p-i.). MBF was recorded with the central bearing point method using a full-bridge strain gauge load cell. Data were analysed off-line using the mean of two peak readings per patient per session. Results: The results indicate that MBF tended to be impaired when replacement dentures were first fitted (n.s.). However, this trend reversed during the first month p-i. for patients with a “moderate” lower ridge resorption of Atwood grade 3 or 4 (n = 5). Patients with more severe lower ridge resorption Atwood grade 5 or 6 (n = 4) showed a significantly lower MBF over the entire observation period (p0.05) and took longer to regain bite strength. Only patients with moderate bone resorption exceeded their pre-insertion level of MBF within the observation period of 6–10 months p-i. Conclusion: The present pilot study suggests that, at least for elderly patients with severe bone resorption, delayed improvement of MBF should be expected with replacement complete dentures.