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Biol Open. 2018 Sep 20;7(9). pii: bio036335. doi: 10.1242/bio.036335.

Axial morphology and 3D neurocranial kinematics in suction-feeding fishes.

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Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman Street, Providence, RI 02912, USA
Friday Harbor Laboratories, University of Washington, 620 University Road, Friday Harbor, WA 98250, USA.
Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman Street, Providence, RI 02912, USA.
School of Aquatic and Fishery Sciences, University of Washington, 1122 Boat Street, Seattle, WA 98105, USA.


Many suction-feeding fish use neurocranial elevation to expand the buccal cavity for suction feeding, a motion necessarily accompanied by the dorsal flexion of joints in the axial skeleton. How much dorsal flexion the axial skeleton accommodates and where that dorsal flexion occurs may vary with axial skeletal morphology, body shape and the kinematics of neurocranial elevation. We measured three-dimensional neurocranial kinematics in three species with distinct body forms: laterally compressed Embiotoca lateralis, fusiform Micropterus salmoides, and dorsoventrally compressed Leptocottus armatus The area just caudal to the neurocranium occupied by bone was 42±1.5%, 36±1.8% and 22±5.5% (mean±s.e.m.; N=3, 6, 4) in the three species, respectively, and the epaxial depth also decreased from E. lateralis to L. armatus Maximum neurocranial elevation for each species was 11, 24 and 37°, respectively, consistent with a hypothesis that aspects of axial morphology and body shape may constrain neurocranial elevation. Mean axis of rotation position for neurocranial elevation in E. lateralis, M. salmoides and L. armatus was near the first, third and fifth intervertebral joints, respectively, leading to the hypothesis of a similar relationship with the number of intervertebral joints that flex. Although future work must test these hypotheses, our results suggest the relationships merit further inquiry.


Axial skeleton; Body shape; Pterygiophore; Supraneural; VROMM; XROMM

Conflict of interest statement

Competing interestsThe authors declare no competing or financial interests.

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