Rhythmic chewing with oral jaws in teleost fishes: a comparison with amniotes

Abstract

SUMMARYIntra-oral prey processing (chewing) using the mandibular jaws occurs more extensively among teleost fishes than previously documented. The lack of muscle spindles, -motoneurons and periodontal afferents in fishes makes them useful for testing hypotheses regarding the relationship between these sensorimotor components and rhythmic chewing in vertebrates. Electromyography (EMG) data from the adductor mandibulae (AM) were used to quantify variation in chew cycle duration in the bowfin Amia, three osteoglossomorphs (bony-tongues), four salmonids and one esocid (pike). All species chewed prey using their oral jaw in repetitive trains of between 3 and 30 consecutive chews, a pattern that resembles cyclic chewing in amniote vertebrates. Variance in rhythmicity was compared within and between lineages using coefficients of variation and Levene's test for homogeneity of variance. These comparisons revealed that some teleosts exhibit degrees of rhythmicity that are comparable to mammalian mastication and higher than in lepidosaurs. Moreover, chew cycle durations in fishes, as in mammals, scale positively with mandible length. Chewing among basal teleosts may be rhythmic because it is stereotyped and inflexible, the result of patterned interactions between sensory feedback and a central pattern generator, because the lack of a fleshy tongue renders jaw-tongue coordination unnecessary and/or because stereotyped opening and closing movements are important for controlling fluid flow in the oral cavity. Supplementary material available online at

Convergence in morphology and masticatory function between the pharyngeal jaws of grass carp,Ctenopharyngodon idella, and oral jaws of amniote herbivores

“…One way to assess the variability of chewing cycle duration is to calculate the coefficient of variation (CV) (Gintof et al, 2010;Ross et al, 2007). Individuals 2, 3 and 4 each had a CV near or below 10% while individual 1 had a CV of 21%.…”

“…Schwenk and Rubega, 2005;Gintof et al, 2010). In evolutionary shifts to herbivory, chewing cycles increase in complexity of the rotational pattern of the jaw, which can increase the translation of one chewing surface relative to the other in the occlusal plane (Reilly et al, 2001).…”

Mammalian Oral Rhythms and Motor Control

“…Although mastication is a mammalian derivation, other non-mammalian species chew rhythmically including teleost fishes (Gintof et al, 2010), some larval amphibians (Larson & Reilly, 2003), and many invertebrates (Marder et al, 2005). Although larval amphibians manifest rhythmic feeding, the adult forms manifest mainly non-rhythmic forms of feeding (Deban et al, 2001).…”

“…The diversity of chewing patterns among all animals is striking; however, this chapter will focus on mammalian chewing or mastication. It is generally believed that the masticatory motor program is conserved across mammals (Langenbach & Van Eijden, 2001) and other vertebrate classes as well (Gintof et al, 2010). Although little comparative work at the neurobiological level has been done, it is likely that the fundamental brain stem circuitry that produces mastication is found in many if not most mammals and other vertebrate classes.…”

“…CV standardizes variation for comparison purposes. It has been used as an uncorrected statistic (equation 1) Ross et al, 2007b) or corrected (Gintof et al, 2010),…”