Ontogenetic scaling of the morphology and biomechanics of the feeding apparatus in the Pacific hagfish Eptatretus stoutii

Authors

  • A. J. Clark,

    Corresponding author
    1. Department of Ecology and Evolutionary Biology, University of California – Irvine, 321 Steinhaus Hall, Irvine, CA 92697, U.S.A.
      Author to whom correspondence should be addressed at present address: Department of Biology, College of Charleston, 58 Coming Street, Charleston, SC 29401, U.S.A. Tel.: +1 843 9534879; email: clarkaj@cofc.edu
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  • A. P. Summers

    1. Department of Ecology and Evolutionary Biology, University of California – Irvine, 321 Steinhaus Hall, Irvine, CA 92697, U.S.A.
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    • Present address: Friday Harbor Laboratories, University of Washington, 620 University Road, Friday Harbor, WA 98250, U.S.A.


Author to whom correspondence should be addressed at present address: Department of Biology, College of Charleston, 58 Coming Street, Charleston, SC 29401, U.S.A. Tel.: +1 843 9534879; email: clarkaj@cofc.edu

Abstract

The form and function of the support skeleton, musculature and teeth were examined in an ontogenetic series of Pacific hagfish Eptatretus stoutii spanning about a six-fold range in total length (LT). Tooth area, feeding apparatus length, basal plate size, theoretical dental plate retractile force, penetration force and applied tooth stress were measured relative to body size. Morphological variables (e.g. tooth area and basal plate size) scaled with positive allometry and functional variables (e.g. retractile force and applied tooth stress) scaled isometrically with LT. These results suggest that juveniles do not undergo ontogenetic dietary changes and consume functionally equivalent prey to adults, although adults can grasp proportionally larger portions of food. Low tooth stress in juveniles and adults imposes mechanical constraints to puncturing and tearing, which are circumvented by a preference for softer prey tissue or the inclusion of knotting behaviours for reducing tougher prey.

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