Four-bar linkage modelling in teleost pharyngeal jaws : computer simulations of bite kinetics
Figure 1: Parasagittal dissection of the branchial arches of S. ocellatus illustrating the multiple bone elements and extensive branchial musculature controlling pharyngognathy set deep within the gill chamber. (395.4Kb)
Figure 3: Upper pharyngeal jaw dissection showing close up lateral view of digital landmarks of anatomical elements used to generate model simulations (A). Overlay depicting the morphometry of digital landmarks making up the links of the proposed four-bar linkage in the upper jaw mechanism (B). (1.550Mb)
Figure 4: PharyngoModel 2.0 application screen showing application control features, linkage morphometric data calculated from input coordinates, simulation results, and a drawing of the linkage positions under the current simulation parameters. (263.9Kb)
Figure 5: Vector diagrams of the lever and linkage mechanisms in the pharyngeal jaws of Sciaenops ocellatus, showing the force vectors of (A) the levator posterior (LP) muscle (levator externus has a similar mechanism), (B) the obliquus posterior (OP), and (C) the obliquus dorsalis 3 (OD). (250.9Kb)
Figure 6: Kinematics of the pharyngeal bite of Sciaenops ocellatus as a function of LP contraction up to 10% of resting length. (261.7Kb)
Figure 7: Kinematics of the pharyngeal bite of Sciaenops ocellatus as a function of LP contraction up to 10% of resting length. (223.6Kb)
Figure 8: Relative bite force potential of the pharyngeal apparatus simulated by the model, expressed as total force assuming a constant 1.0N input force from each muscle (4N total for the four muscles) during a 10% shortening of the LP. (260.4Kb)
Grubich, Justin R.
Westneat, Mark W.
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The pharyngeal arches of the red drum (Sciaenops ocellatus) possess large toothplates and a complex musculoskeletal design for biting and crushing hard prey. The morphology of pharyngeal apparatus is described from dissections of six specimens, with a focus on the geometric conformation of contractile and rotational elements. Four major muscles operate the rotational 4th epibranchial (EB4) and 3rd pharyngobranchial (PB3) elements to create pharyngeal bite force, including the levator posterior (LP), levator externus 3/4 (LE), obliquus posterior (OP), and 3rd obliquus dorsalis (OD). A biomechanical model of upper pharyngeal jaw biting is developed using lever mechanics and four-bar linkage theory from mechanical engineering. A pharyngeal four-bar linkage is proposed that involves the posterior skull as the fixed link, the LP muscle as input link, the epibranchial bone as coupler link, and the toothed pharyngobranchial as output link. We used a computer model to simulate contraction of the four major muscles, with the LP as the dominant muscle whose length determined the position of the linkage. When modeling lever mechanics, we found that the effective mechanical advantages of the pharyngeal elements were low, resulting in little resultant bite force. In contrast, the force advantage of the four-bar linkage was relatively high, transmitting approximately 50% of the total muscle force to the bite between the toothplates. Pharyngeal linkage modeling enables quantitative functional morphometry of a key component of the fish feeding system, and the model is now available for ontogenetic and comparative analyses of fishes with pharyngeal linkage mechanisms.
Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of Anatomical Society of Great Britain and Ireland for personal use, not for redistribution. The definitive version was published in Journal of Anatomy 209 (2006): 79-92, doi:10.1111/j.1469-7580.2006.00551.x.