Engulfing mechanics of fin whales

Abstract

The grooved throat wall of fin whales, Balaenoptera physalus, extends tremendously during feeding causing the whale to expand its profile from a cigar shape to the shape of an elongated, bloated tadpole. Ventral groove blubber associated with the engulfing feeding mechanism can be extended reversibly to as much as 4 times its resting length in the circumferential direction, and to 1.5 times its resting length along the long axis of the body. The muscle in the throat wall can be reversibly extended up to 3 times its resting length. Both these tissues have large amounts of the protein elastin in their microstructures that may function in retracting the expanded buccal cavity. Calculations of forces contributing to the expansion of the buccal cavity show that the engulfing process in feeding can be powered solely by the speed of swimming.

Adaptations of the cetacean hyolingual apparatus for aquatic feeding and thermoregulation

“…Rather than expanding a space to create negative pressure and draw water in, rorquals unlock their jaws and relax adductor musculature to open the mouth (at least 308, and up to 908), which suddenly fills with water in much the same way as a bag is opened by rapidly pulling it through air, by both mandibular depression and slight cranial elevation (Arnold et al, 2005;Kot, 2005). Positive inertial pressure forces open the space into which water and prey flow; seawater is passively enveloped rather than displaced forward or sucked internally (Orton and Brodie, 1987). Smaller rorquals may retract the tongue to varying degrees to pull in a water stream that fills the oral sac toward the rear rather than sides (Pivorunas, 1979), avoiding a wave of resistant pressure that could disperse prey at the entrance to the mouth and thus interfere with capture.…”

Discovery of a sensory organ that coordinates lunge feeding in rorqual whales

“…At the largest scale, rorqual whales (Balaenopteridae) engulf and filter prey-laden water by lunge feeding 4 , a strategy that is unique among vertebrates 1 . Lunge feeding is facilitated by several morphological specializations, including bilaterally separate jaws that loosely articulate with the skull 5,6 , hyper-expandable throat pleats, or ventral groove blubber 7 , and a rigid y-shaped fibrocartilage structure branching from the chin into the ventral groove blubber 8 . The linkages and functional coordination among these features, however, remain poorly understood.…”

“…These papillae show the hallmarks of a mechanoreceptor, containing nerves and encapsulated nerve termini. Histological, anatomical and kinematic evidence indicate that this sensory organ responds to both the dynamic rotation of the jaws during mouth opening and closure, and ventral groove blubber 7 expansion through direct mechanical linkage with the y-shaped fibrocartilage structure. Along with vibrissae on the chin 9 , providing tactile prey sensation, this organ provides the necessary input to the brain for coordinating the initiation, modulation and end stages of engulfment, a paradigm that is consistent with unsteady hydrodynamic models and tag data from lunge-feeding rorquals [10][11][12][13] .…”

“…During a lunge, rorquals accelerate to high speed and open their jaws in a complex sequence of rotation around three orthogonal axes 6 , including an overall gape angle that approaches 90 degrees at the peak of the lunge 5 . Dynamic pressure imposed on the floor of the mouth forces inversion of the tongue 18 and expansion of the ventral groove blubber (VGB) to accommodate the engulfed water 5,7 . Hydromechanical models suggest that the expansion of the oropharyngeal cavity (or ventral pouch 8 ) requires active resistance, in a highly coordinated fashion, by eccentric action from musculature associated with the VGB [10][11][12][13] .…”

Convergent Evolution Driven by Similar Feeding Mechanics in Balaenopterid Whales and Pelicans

“…This element of mandibular design may be critical for resisting jaw fracture during feeding. Orton and Brodie (1987) discussed the elastic properties of rorqual VGB, but the mechanical properties of the pelican gular pouch have not been examined. Here, we present the first data on the material properties of Brown Pelican gular pouch tissue, as well as the relative bending resistance of the Brown Pelican mandible in dorsoventral and mediolateral orientations.…”