Abstract
Advances in imaging and modeling facilitate the calculation of biomechanical forces in biological specimens. These factors play a significant role during ontogenetic development of cichlid pharyngeal jaws, a key innovation responsible for one of the most prolific species diversifications in recent times. MicroCT imaging of radiopaque-stained vertebrate embryos were used to accurately capture the spatial relationships of the pharyngeal jaw apparatus in two cichlid species (Haplochromis elegans and Amatitlania nigrofasciata) for the purpose of creating a time series of developmental stages using finite element models, which can be used to assess the effects of biomechanical forces present in a system at multiple points of its ontogeny. Changes in muscle vector orientations, bite forces, force on the neurocranium where cartilage originates, and stress on upper pharyngeal jaws are analyzed in a comparative context. In addition, microCT scanning revealed the presence of previously unreported cement glands in A. nigrofasciata. The data obtained provide an underrepresented dimension of information on physical forces present in developmental processes and assist in interpreting the role of developmental dynamics in evolution.
Highlights
Development utilizes both genetically controlled and context-dependent cues, such as generic cell and tissue interactions with the physiochemical environment and interactions among tissues themselves [1,2,3,4]
The induction of bone or cartilage has been found to be caused by mechanical tension and compression, and biomechanical forces can have a role in altering structures in the adult
Isometric growth of the head, and the neurocranium in particular, results in a shifting of muscle contractions angles. These differ between species, as A. nigrofasciata has a more rounded head shape during early development compared to H. elegans, which is more elongated along the dorso-ventral axis
Summary
Development utilizes both genetically controlled and context-dependent cues, such as generic cell and tissue interactions with the physiochemical environment and interactions among tissues themselves [1,2,3,4]. These non-programmed aspects of development are called upon by the developmental system based on local signals and can result in changes across the entire organism or remain confined to distinct parts. The induction of bone or cartilage has been found to be caused by mechanical tension and compression, and biomechanical forces can have a role in altering structures in the adult
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