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The hydrodynamic regime drives flow reversals in suction-feeding larval fishes during early ontogeny.

ABSTRACT: Fish larvae are the smallest self-sustaining vertebrates. As such, they face multiple challenges that stem from their minute size, and from the hydrodynamic regime in which they dwell. This regime, of intermediate Reynolds numbers, was shown to affect the swimming of larval fish and impede their ability to capture prey. Prey capture is impeded because smaller larvae produce weaker suction flows, exerting weaker forces on the prey. Previous observations on feeding larvae also showed prey exiting the mouth after initially entering it (hereafter 'in-and-out'), although the mechanism causing such failures had been unclear. In this study, we used numerical simulations to investigate the hydrodynamic mechanisms responsible for the failure to feed caused by this in-and-out prey movement. 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 revealed that for small larvae which expand their mouth slowly, fluid entering the mouth cavity is expelled through the mouth before it is closed, resulting in flow reversal at the orifice. This relative efflux of water through the mouth was >8% of the influx through the mouth for younger ages. However, similar effluxes were found when we simulated slow strikes by larger fish. The simulations can explain the observations of larval fish failing to feed because of the in-and-out movement of the prey. These results further highlight the importance of transporting the prey from the gape deeper into the mouth cavity in determining suction-feeding success.

SUBMITTER: Krishnan K

PROVIDER: S-EPMC7240303 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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The hydrodynamic regime drives flow reversals in suction-feeding larval fishes during early ontogeny.

Krishnan Krishnamoorthy K Nafi Asif Shahriar AS Gurka Roi R Holzman Roi R

The Journal of experimental biology 20200511 Pt 9

Fish larvae are the smallest self-sustaining vertebrates. As such, they face multiple challenges that stem from their minute size, and from the hydrodynamic regime in which they dwell. This regime, of intermediate Reynolds numbers, was shown to affect the swimming of larval fish and impede their ability to capture prey. Prey capture is impeded because smaller larvae produce weaker suction flows, exerting weaker forces on the prey. Previous observations on feeding larvae also showed prey exiting ...[more]

PMID: 32253288

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Project description:The complex interplay between form and function forms the basis for generating and maintaining organismal diversity. Fishes that rely on suction-feeding for prey capture exhibit remarkable phenotypic and trophic diversity. Yet the relationships between fish phenotypes and feeding performance on different prey types are unclear, partly because the morphological, biomechanical, and hydrodynamic mechanisms that underlie suction-feeding are complex. Here we demonstrate a general framework to investigate the mapping of multiple phenotypic traits to performance by mapping kinematic variables to suction-feeding capacity. Using a mechanistic model of suction-feeding that is based on core physical principles, we predict prey capture performance across a broad range of phenotypic trait values, for three general prey types: mollusk-like prey, copepod-like prey, and fish-like prey. Mollusk-like prey attach to surfaces, copepod-like prey attempt to escape upon detecting the hydrodynamic disturbance produced by the predator, and fish-like prey attempt to escape when the predator comes within a threshold distance. This approach allowed us to evaluate suction-feeding performance for any combination of six key kinematic traits, irrespective of whether these trait combinations were observed in an extant species, and to generate a multivariate mapping of phenotype to performance. We used gradient ascent methods to explore the complex topography of the performance landscape for each prey type, and found evidence for multiple peaks. Characterization of phenotypes associated with performance peaks indicates that the optimal kinematic parameter range for suction-feeding on different prey types are narrow and distinct from each other, suggesting different functional constraints for the three prey types. These performance landscapes can be used to generate hypotheses regarding the distribution of extant species in trait space and their evolutionary trajectories toward adaptive peaks on macroevolutionary fitness landscapes.

Dataset Information

The hydrodynamic regime drives flow reversals in suction-feeding larval fishes during early ontogeny.

Publications

The hydrodynamic regime drives flow reversals in suction-feeding larval fishes during early ontogeny.

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