Decoupled ontogeny of in vivo bite force and mandible morphology reveals effects of weaning and sexual maturation in mice

Abstract

The link between performance, morphology and their sources of variation is a major target of evolutionary functional biology. In vertebrates, many studies have linked in vivo bite force to skull morphology, mostly at the interspecific level. Within species, however, the ontogeny of bite force, in relation to the development of the mandible, remains poorly known, despite its relevance for life history and for the co-evolution of form and function. Here, ontogenetic trajectories of bite force, correlated with mandible size and shape, are reported for the first time in a wild-derived colony of laboratory mice. Bite forces were measured in vivo and mandible morphology was assessed using geometric morphometrics. Most coordinated changes in morphology and in vivo bite force occur during the first stages of growth, prior to weaning. Mandible shape stabilizes after day 23. The increases in mandible size and body mass slow down around day 40, but still increase during adulthood. Despite slowing down after weaning, bite force increases through a second phase during sexual maturation (days 30–40). This may be linked to the progressive tempering of weaning stress, continued growth and synchronization of the muscular and osteological systems, together with hormonal changes, as we observed a concomitant appearance of sexual dimorphism.

Sex‐specific ontogenetic patterns of cranial morphology, theoretical bite force, and underlying jaw musculature in fishers and American martens

“…Growth in cranial size is often found to be the primary way to increase bite force across ontogeny (La Croix et al ., 2011b; Santana and Miller, 2016; Law et al ., 2016b; Ginot et al ., 2020). However, many carnivorans also exhibit significant cranial shape changes across ontogeny such as the development of the sagittal and nuchal crests (Tanner et al ., 2010; La Croix et al ., 2011a; Tarnawski et al ., 2013; Tarnawski et al ., 2015).…”

Functional constraints channel mandible shape ontogenies in rodents

“…Thereby, the mandible of the mouse undergoes major changes from the first stage (7–14 days). Indeed, it has already been shown that the bite force of mouse juveniles increases well before food weaning [55], which may explain early bone remodelling [56]. Early competition among pups and lower parental care in mice [10,57,58] may explain this acceleration of shape development and the correlated functional changes in mice compared with the two other species.…”

Commonalities and evolutionary divergences of mandible shape ontogenies in rodents

“…The feeding system must change from the sucking movement to active chewing in only a few days. In mice, bite force increases drastically in the days preceding weaning (Ginot et al, 2020). In the Hystricomorpha species, parental care is different, with long behavioural weaning and less brutal dietary weaning, over a much longer period (Wolff & Sherman, 2008).…”