Premium
The Ontogeny of Mechanical Advantage in the Masticatory System
Author(s) -
Cobb Samuel,
Smith Olivia,
Fitton Laura
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.865.6
Subject(s) - masticatory force , ontogeny , gorilla , bite force quotient , pongo pygmaeus , biology , skull , anatomy , troglodytes , zoology , orthodontics , medicine , ecology , paleontology , genetics
The skull changes shape and increases in size during ontogeny, and has a number of potentially competing systems and functions to accommodate or maintain as it changes, including the masticatory system. The functional efficiency of the masticatory system is determined by several factors including the mechanical advantage (MA) of the jaw closing muscles. As skull length increases with age, we expect the out lever (OL) to increase for anterior bites and less so for posterior bites. Unless muscle in levers (IL) are reorganised, we predict MA to decrease with age in each species. We test this prediction for temporalis and masseter across a range of catarrhine primates with a variety of diets. IL and OL lengths, and MA were calculated from 3D coordinate data from Pan troglodytes , Gorilla gorilla , Pongo pygmaeus , Cercopithecus nictitans and Colobus satanas at 3 dental eruption stages. The results confirm the prediction that anterior bite OLs increase more than posterior bite OLs during ontogeny in all species; unexpectedly anterior bite MAs vary little with age. Although posterior bite OLs vary little, posterior bite MAs increase with age, except in Pongo . Based on the changes in OLs, the MA results can only be accounted for by a reorganisation of ILs during ontogeny. Given these MA results and that muscles should be absolutely larger in adults, it is expected that younger individuals will have reduced masticatory capabilities and a less mechanically resistant feeding behaviour in comparison to adults; or cope with the mechanical demands of an adult diet through other mechanisms, such as the dental topography of unworn teeth and internal muscle architecture.