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Hydrodynamic regime drives flow reversals in suction feeding larval fishes during early ontogeny

Krishnamoorthy Krishnan,A. Nafi,R. Gurka,R. Holzman

Published 2019 in bioRxiv

ABSTRACT

Fish larvae are the smallest self-sustaining vertebrates. As such, they face multiple challenge that stem from their minute size, and from the hydrodynamic regime in which they dwell. This regime of intermediate Reynolds numbers (Re) was shown to affect the swimming of larval fish and impede their ability to capture prey. Numerical simulations indicate that the flow fields external to the mouth in younger larvae result in shallower spatial gradients, limiting the force exerted on the prey. However, observations on feeding larvae suggest that failures in prey capture can also occur during prey transport, although the mechanism causing these failures is unclear. We combine high-speed videography and numerical simulations to investigate the hydrodynamic mechanisms that impede prey transport in larval fishes. Detailed kinematics of the expanding mouth during prey capture by larval Sparus aurata were used to parameterize age-specific numerical models of the flows inside the mouth. These models reveal that, for small larvae that slowly expand their mouth, not all the fluid that enters the mouth cavity is expelled through the gills, resulting in flow reversal at the mouth orifice. This efflux at the mouth orifice was highest in the younger ages, but was also high (>8%) in slow strikes produced by larger fish. Our modeling explains the observations of “in-and-out” events in larval fish, where prey enters the mouth but is not swallowed. It further highlights the importance of prey transport as an integral part in determining suction feeding success.

PUBLICATION RECORD

  • Publication year

    2019

  • Venue

    bioRxiv

  • Publication date

    2019-09-18

  • Fields of study

    Biology, Environmental Science

  • Identifiers
    DOI 10.1101/771436
  • External record

    Open on Semantic Scholar

  • Source metadata

    Semantic Scholar

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