The benefits of planar circular mouths on suction feeding performance

Abstract

Suction feeding is the most common form of prey capture across aquatic feeding vertebrates and many adaptations that enhance efficiency and performance are expected. Many suction feeders have mechanisms that allow the mouth to form a planar and near-circular opening that is believed to have beneficial hydrodynamic effects. We explore the effects of the flattened and circular mouth opening through computational fluid dynamics simulations that allow comparisons with other mouth profiles. Compared to mouths with lateral notches, we find that the planar mouth opening results in higher flow rates into the mouth and a region of highest flow that is positioned at the centre of the mouth aperture. Planar mouths provide not only for better total fluid flow rates through the mouth but also through the centre of the mouth near where suction feeders position their prey. Circular mouths are shown to provide the quickest capture times for spherical and elliptical prey because they expose the prey item to a large region of high flow. Planar and circular mouths result in higher flow velocities with peak flow located at the centre of the mouth opening and they maximize the capacity of the suction feeders to exert hydrodynamic forces on the prey.

Biting disrupts integration to spur skull evolution in eels

“…As information on prey capture behaviour in eels is limited, feeding mode was determined by examining a suite of morphological traits that are well known to differentiate biters from suction feeders 26,62,63 . To avoid circularity in our analysis, we scored four discrete cranial traits that do not overlap with the skeletal elements measured as part of our main analysis: oral teeth, PMx-Et-V teeth, hyomandibular orientation and mouth shape.…”

“…The mouth opening is rounded (0), semi-rounded (1), notched (2) or deeply notched (3). A rounded opening is critical to directing water flow in front of the mouth, while lateral notches make suction production much less efficient 26,62,63 . The degree of roundedness or notching is obvious in lateral view when the mouth is fully opened.…”

Does Feeding Behavior Facilitate Trophic Niche Partitioning in Two Sympatric Sucker Species from the American Southwest?

“…The red dotted line (tranverse to the mouth) was used to assess gape ratio (a proxy for the circularity of the mouth) and gape area. could "choose" to produce a smaller gape and greater cranial rotation, as an increase in the magnitude of these two traits is associated with increased suction performance (Gibb and FerryGraham 2005;Wainwright et al 2007;Skorczewski et al 2012). In this manner, modulation (Liem 1980;Nemeth 1997;Oufiero et al 2012) of prey-capture behavior could compensate for the potential handicaps imposed by a specialized feeding apparatus.…”

“…For example, the "scraping plate" of the lower jaw and the wide mouth-gape of the desert sucker may enhance its ability to acquire attached algae and associated interstitial invertebrates. However, that same morphology could become a liability when a desert sucker attempts to consume individual prey items by drawing them into the mouth via suction, because a smaller anatomical gape is optimal under those circumstances (Skorczewski et al 2012). …”

“…Variables are given here as mean values ‫ע‬ 1 SEM; an asterisk indicates a significant difference as analyzed with a one-tailed Student's t-test. more rounded gape, and greater buccal expansion when capturing unattached prey, because these behavioral traits should enhance suction-feeding performance (Gibb and Ferry-Graham 2005;Wainwright et al 2007;Skorczewski et al 2012). (3) We hypothesize that desert suckers employ an invariant feeding behavior to capture a variety of prey types, while Sonora suckers have a repertoire of behaviors that they employ to obtain a variety of prey types.…”