Modeling the jaw mechanism of Pleuronichthys verticalis: The morphological basis of asymmetrical jaw movements in a flatfish

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6 Citations (Scopus)

Abstract

Several flatfish species exhibit the unusual feature of bilateral asymmetry in prey capture kinematics. One species, Pleuronichthys verticalis, produces lateral flexion of the jaws during prey capture. This raises two questions: 1) How are asymmetrical movements generated, and 2) How could this unusual jaw mechanism have evolved? In this study, specimens were dissected to determine which cephalic structures might produce asymmetrical jaw movements, hypotheses were formulated about the specific function of these structures, physical models were built to test these hypotheses, and models were compared with prey capture kinematics to assess their accuracy. The results suggest that when the neuro-cranium rotates dorsally the premaxillae slide off the smooth, rounded surface of the vomer (which is angled toward the blind, or eyeless, side) and are "launched" anteriorly and laterally. The bilaterally asymmetrical trajectory of the upper jaw is determined by the orientation of the "launch pad," the vomer. During lower jaw depression, the mandibles rotate about their articulations with the quadrate bones of the suspensoria. The quadrato-mandibular joint is positioned farther anteriorly on the eye side than on the blind side, and this asymmetry deflects the lower jaw toward the blind side. Asymmetry in the articular surfaces of the lower jaw augments this effect. Thus, it appears that fish with intermediate forms of this asymmetrical movement could have evolved from symmetrical ancestors via a few key morphological changes. In addition, similar morphological modifications have been observed in other fish taxa that also produce jaw flexion during feeding, which suggests that there may be convergence in the basic mechanism of asymmetry.

Original languageEnglish (US)
Pages (from-to)1-12
Number of pages12
JournalJournal of Morphology
Volume256
Issue number1
DOIs
StatePublished - Apr 1 2003

Fingerprint

Flatfishes
Pleuronectiformes
Jaw
jaws
Vomer
Biomechanical Phenomena
kinematics
Fishes
Joints
Maxilla
mandible (bone)
Pleuronichthys verticalis
physical models
Mandible
Skull
fish
joints (animal)
trajectories
Head
ancestry

Keywords

  • Asymmetry
  • Feeding
  • Flatfish
  • Modeling

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Developmental Biology
  • Anatomy

Cite this

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title = "Modeling the jaw mechanism of Pleuronichthys verticalis: The morphological basis of asymmetrical jaw movements in a flatfish",
abstract = "Several flatfish species exhibit the unusual feature of bilateral asymmetry in prey capture kinematics. One species, Pleuronichthys verticalis, produces lateral flexion of the jaws during prey capture. This raises two questions: 1) How are asymmetrical movements generated, and 2) How could this unusual jaw mechanism have evolved? In this study, specimens were dissected to determine which cephalic structures might produce asymmetrical jaw movements, hypotheses were formulated about the specific function of these structures, physical models were built to test these hypotheses, and models were compared with prey capture kinematics to assess their accuracy. The results suggest that when the neuro-cranium rotates dorsally the premaxillae slide off the smooth, rounded surface of the vomer (which is angled toward the blind, or eyeless, side) and are {"}launched{"} anteriorly and laterally. The bilaterally asymmetrical trajectory of the upper jaw is determined by the orientation of the {"}launch pad,{"} the vomer. During lower jaw depression, the mandibles rotate about their articulations with the quadrate bones of the suspensoria. The quadrato-mandibular joint is positioned farther anteriorly on the eye side than on the blind side, and this asymmetry deflects the lower jaw toward the blind side. Asymmetry in the articular surfaces of the lower jaw augments this effect. Thus, it appears that fish with intermediate forms of this asymmetrical movement could have evolved from symmetrical ancestors via a few key morphological changes. In addition, similar morphological modifications have been observed in other fish taxa that also produce jaw flexion during feeding, which suggests that there may be convergence in the basic mechanism of asymmetry.",
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N2 - Several flatfish species exhibit the unusual feature of bilateral asymmetry in prey capture kinematics. One species, Pleuronichthys verticalis, produces lateral flexion of the jaws during prey capture. This raises two questions: 1) How are asymmetrical movements generated, and 2) How could this unusual jaw mechanism have evolved? In this study, specimens were dissected to determine which cephalic structures might produce asymmetrical jaw movements, hypotheses were formulated about the specific function of these structures, physical models were built to test these hypotheses, and models were compared with prey capture kinematics to assess their accuracy. The results suggest that when the neuro-cranium rotates dorsally the premaxillae slide off the smooth, rounded surface of the vomer (which is angled toward the blind, or eyeless, side) and are "launched" anteriorly and laterally. The bilaterally asymmetrical trajectory of the upper jaw is determined by the orientation of the "launch pad," the vomer. During lower jaw depression, the mandibles rotate about their articulations with the quadrate bones of the suspensoria. The quadrato-mandibular joint is positioned farther anteriorly on the eye side than on the blind side, and this asymmetry deflects the lower jaw toward the blind side. Asymmetry in the articular surfaces of the lower jaw augments this effect. Thus, it appears that fish with intermediate forms of this asymmetrical movement could have evolved from symmetrical ancestors via a few key morphological changes. In addition, similar morphological modifications have been observed in other fish taxa that also produce jaw flexion during feeding, which suggests that there may be convergence in the basic mechanism of asymmetry.

AB - Several flatfish species exhibit the unusual feature of bilateral asymmetry in prey capture kinematics. One species, Pleuronichthys verticalis, produces lateral flexion of the jaws during prey capture. This raises two questions: 1) How are asymmetrical movements generated, and 2) How could this unusual jaw mechanism have evolved? In this study, specimens were dissected to determine which cephalic structures might produce asymmetrical jaw movements, hypotheses were formulated about the specific function of these structures, physical models were built to test these hypotheses, and models were compared with prey capture kinematics to assess their accuracy. The results suggest that when the neuro-cranium rotates dorsally the premaxillae slide off the smooth, rounded surface of the vomer (which is angled toward the blind, or eyeless, side) and are "launched" anteriorly and laterally. The bilaterally asymmetrical trajectory of the upper jaw is determined by the orientation of the "launch pad," the vomer. During lower jaw depression, the mandibles rotate about their articulations with the quadrate bones of the suspensoria. The quadrato-mandibular joint is positioned farther anteriorly on the eye side than on the blind side, and this asymmetry deflects the lower jaw toward the blind side. Asymmetry in the articular surfaces of the lower jaw augments this effect. Thus, it appears that fish with intermediate forms of this asymmetrical movement could have evolved from symmetrical ancestors via a few key morphological changes. In addition, similar morphological modifications have been observed in other fish taxa that also produce jaw flexion during feeding, which suggests that there may be convergence in the basic mechanism of asymmetry.

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