Functional morphology of lingual protrusion in marine toads (Bufo marinus)

Abstract

Bufo marinus catches its prey by stiffening the intrinsic muscles of the tongue, rapidly flipping the tongue out of the mouth. High-speed cinematography synchronized with computer-analyzed electromyograms (EMGs)shows that during the flip the tongue is supported by the M. genioglossus medialis and that this muscle stiffens into a rod when stimulated. Coincident stiffening of the transversely arranged M. genioglossus basalis provides a wedge under the anterior tip of this rod. Stiffening of the M. submentalis depresses the mandibular symphysis and brings the dentary tips together. The M. submentalis also acts on the wedge of the basalis to raise and rotate the rigid rod of the medialis over the symphysial attachment. The tip of this lingual rod carries along the pad and soft tissues of the tongue. The lingual pad, positioned the posterodorsal portion of the resting tongue, rotates during eversion so that its dorsal surface impacts onto the prey object. Retraction starts by contraction of the elongate, parallel fibers of the M. hyoglossus; this retracts the medical sulcus of the pad and holds the prey by a suction cup-like effect. The extensibility of the buccal membranes allows the pad to be retracted first; it reaches the posterior portion of the buccal cavity before the still-rigid, backward rotating M. genioglossus has reached the level of the symphysis. Protraction of the hyoid facilitates the extension of the M. hyoglossus. The M. sternohyoideus only retracts the hyoid and stabilizes it when the tongue starts to pull posteriorly; it does not assist tongue protrusion. The Mm. petrohyoideus and omohyoideus show only incidental activity, and the M. depressor mandibulae participate in mouth opening but is not otherwise involved in the flip. Previous hypotheses of the flipping mechanism are reviewed and evaluated.

Monophyly and affinities of albanerpetontid amphibians (Temnospondyli; Lissamphibia)

“…In anurans the mentomeckelian is among the last bones to appear at metamorphosis (see review by Trueb, 1985). The mentomeckelian remains discrete in most anuran taxa, where movement of these paired bones aids both in depressing the symphysis during protrusion of the tongue for feeding (Gans & Gorniak, 1982) and in closing the external nares during respiration (Gans & Pyles, 1983). The absence of an ossified mentomeckelian in some pipoids is derived within anurans and is associated with modifications to the tongue ( W e b & Cannatella, 1982).…”

Possible neural network mediating jaw opening during prey-catching behavior of the frog

“…However, its contribution to the prey-catching behavior is more complex as the activity level of muscle contraction is changing continuously during the execution of tongue prehension behavior (Gans and Gorniak, 1982). High-speed cinematography synchronized with computeranalyzed electromyograms (EMGs) revealed that the first peak of the contraction in depressor mandibulae muscle appeared in the preparatory phase of prey-catching behavior prior to mouth opening when the activity level of muscle fluctuated between 10 and 100% (Gans and Gorniak, 1982).…”

“…In later phase of retraction the activity of depressor mandibulae drops and then becomes silent before the tongue reaches the back of the oral cavity. Taking into consideration the very quick time course of prey-catching behavior (Gans and Gorniak, 1982), we supposed that feedback and feedforward modulations of rapidly changing activity of the depressor mandibulae muscle could be provided via the monosynaptic sensory input transported by the trigeminal nerve to the facial motoneurons.…”

“…Although the possible influence of the primary afferents on the activity of jaw opening muscle is not yet determined, direct contacts have been verified between sensory fibers and various motoneurons supplying jaw closing and tongue muscles as well as those involved in swallowing (Deak et al, 2009;Kecskes et al, 2013Kecskes et al, , 2015Matesz et al, 2008). The jaw opening is executed by the contraction of depressor mandibulae muscle (DMm) under the control of the facial nerve (Gans and Gorniak, 1982;Gaupp, 1904). The possible candidates for sensory inputs to facial motoneurons innervating depressor mandibulae muscle are conveyed by hypoglossal and trigeminal nerves.…”

Aerial and aquatic feeding in the silver arawana, Osteoglossum bicirrhosum

“…Many organisms, however, exploit prey in both aquatic and terrestrial environments. Such versatility in feeding behaviour can exist concomitantly with discrete metamorphic stages (Gans & Gorniak 1982, Nishikawa & Cannatella 1991, Reilly 1996, or within a single life-history stage (Summers et al 1998, Deban & Marks 2002, Luiselli et al 2002. Few kinematic and behavioural studies have focused specifically on fishes that feed in both aquatic and aerial environments during the same life history stage (Hyatt 1971, Zahl et al 1977, Seghers 1978, Sponder & Lauder 1981.…”