Feeding biomechanics of the cownose ray, Rhinoptera bonasus, over ontogeny

Abstract

Growth affects the performance of structure, so the pattern of growth must influence the role of a structure and an organism. Because animal performance is linked to morphological specialization, ontogenetic change in size may influence an organism's biological role. High bite force generation is presumably selected for in durophagous taxa. Therefore, these animals provide an excellent study system for investigating biomechanical consequences of growth on performance. An ontogenetic series of 27 cownose rays (Rhinoptera bonasus) were dissected in order to develop a biomechanical model of the feeding mechanism, which was then compared with bite forces measured from live rays. Mechanical advantage of the feeding apparatus was generally conserved throughout ontogeny, while an increase in the mass and cross-sectional area of the jaw adductors resulted in allometric gains in bite force generation. Of primary importance to forceful biting in this taxon is the use of a fibrocartilaginous tendon associated with the insertion of the primary jaw adductor division. This tendon may serve to redirect muscle forces anteriorly, transmitting them within the plane of biting. Measured bite forces obtained through electrostimulation of the jaw adductors in live rays were higher than predicted, possibly due to differences in specific tension of actual batoid muscle and that used in the model. Mass-specific bite forces in these rays are the highest recorded for elasmobranchs. Cownose rays exemplify a species that, through allometric growth of bite performance and morphological novelties, have expanded their ecological performance over ontogeny.

Morphology does not predict performance: jaw curvature and prey crushing in durophagous stingrays

“…In addition to the musculoskeletal differences among these stingrays, we might expect that the tooth interdigitation pattern, long recognized as a taxonomic character (Claeson et al, 2010), has some effect on crushing performance. Regardless, the forces necessary to crush any of the examined live prey (from 22 to 486 N, peak loading) were well within the performance bounds (>500 N) calculated for Rhinoptera bonasus, the only myliobatid ray for which bite force has been examined to date (Kolmann et al, 2015). However, evidence by Fisher et al (2011) has shown that Rhinoptera can consume some large oysters requiring in excess of 800-1000 N to crush.…”

Do sharks exhibit heterodonty by tooth position and over ontogeny? A comparison using elliptic Fourier analysis

“…Traditionally, tooth function in elasmobranchs has been inferred from morphology (Cappetta, , ; Frazzetta, ), but recent studies that have incorporated measures of performance show that this relationship is complex (Corn, Farina, Brash, & Summers, ; Huber, Claes, Mallefet, & Herrel, ; Whitenack & Motta, ). The attribution of ecology to morphology has been straightforward in some species, such as white sharks ( Carcharodon carcharias ; Ferrara et al, ; French et al, ), sandtiger sharks ( Carcharias taurus ; Ferrara et al, ), horn sharks ( Heterodontus francisci ; Huber, Eason, Hueter, & Motta, ; Summers, Ketcham, & Rowe, ), bonnethead sharks ( Sphyrna tiburo ; Mara, Motta, & Huber, ; Wilga & Motta, ), and cownose rays ( Rhinoptera bonasus ; Kolmann, Huber, Motta, & Grubbs, ). However, the traditional method of attributing form to function has not been helpful for other elasmobranchs.…”

Dry versus wet and gross: Comparisons between the dry skull method and gross dissection in estimations of jaw muscle cross‐sectional area and bite forces in sea otters

“…Additionally, some species, despite their interesting biology or critical phylogenetic position, are poor or risky experimental subjects due to their unpredictable or aggressive, defensive behavior (but see Erickson, Lappin, Parker, & Vliet, ; Gignac & Erickson, ). As a result, many researchers have turned to biomechanical models where the feeding apparatus is modeled as a lever system and quantitative descriptions of the craniomandibular structure and jaw adductor musculature are used as parameters to estimate bite forces (e.g., Davis, Santana, Dumont, & Grosse, ; Gignac & Erickson, ; Hartstone‐Rose, Perry, & Morrow, ; Kolmann, Huber, Motta, & Grubbs, ). These models not only estimate bite force but also allow study of the muscular and morphological components that contribute to generating bite force.…”