Prey capture in the lizard Agama stellio

Abstract

Prey capture in Agama stellio was recorded by high-speed video in combination with the electrical activity of both jaw and hyolingual muscles. Quantification of kinematics and muscle activity patterns facilitated their correlation during kinematic phases. Changes in angular velocity of the gape let the strike be subdivided into four kinematic phases: slow open (SOI and SOII), fast open (FO), fast close (FC), and slow close-power stroke (SC/PS). The SOI phase is marked by initial activity in the tongue protractor, the hyoid protractor, and the ring muscle. These muscles project the tongue beyond the anterior margin of the jaw. During the SOII phase, a low level of activity in the jaw closers correlates with a decline of the jaw-opening velocity. Next, bilateral activity in the jaw openers defines the start of the FO phase. This activity ends at maximal gape. Simultaneously, the hyoid retractor and the hyoglossus become active, causing tongue retraction during the FO phase. At maximal gape, the jaw closers contract simultaneously, initiating the FC phase. After a short pause, they contract again and the prey is crushed during the SC/PS phase. Our results support the hypothesis of tongue projection in agamids by Smith ([1988] J. Morphol. 196:157-171), and show some striking similarities with muscle activity patterns during the strike in chameleons (Wainwright and Bennett [1992a] J. Exp. Biol. 168:1-21). Differences are in the activation pattern of the hyoglossus. The agamid tongue projection mechanism appears to be an ideal mechanical precursor for the ballistic tongue projection mechanism of chameleonids; the key derived feature in the chameleon tongue projection mechanism most likely lies in the changed motor pattern controlling the hyoglossus muscle. © 1995 Wiley-Liss, Inc.

Comparative study of the innervation patterns of the hyobranchial musculature in three iguanian lizards: Sceloporus undulatus, Pseudotrapelus sinaitus, and Chamaeleo jacksonii

“…The general arrangement of the hyobranchial musculature of these three lizards showed no major departures from previous descriptions of other phrynosomatids (Sanders, 1874;Jenkins and Tanner, 1968;Secoy, 1971;Tanner and Avery, 1982;Meyers and Nishikawa, 2000), agamids (Tanner and Avery, 1982;Smith, 1988;Herrel et al, 1995), or chamaeleonids (Houston, 1828;Gnanamuthu, 1930;Lubosch, 1932Lubosch, , 1933Zoond, 1933;Bell, 1989;Herrel et al, 2001). However, we did note the presence of the GGI in S. undulatus, which has not been previously noted in other iguanid (sensu lato) or phrynosomatid lizards (Oelrich, 1956;Secoy, 1971;Tanner and Avery, 1982;Schwenk, 1988;Delheusy et al, 1994;see Schwenk, 2000a, for an overview).…”

“…As chameleons possess the unique ability to ballistically project the tongue out of the mouth, they have been the subject of numerous morphological studies over the past two centuries (Houston, 1828;Rice, 1973;Bell, 1989;see Herrel et al, 2001, for an overview). Although it is generally assumed that chameleons are most closely related to agamids (Moody, 1980;Estes et al, 1988;Schwenk, 1988;Macey et al, 2000a, b), until relatively recently the morphological changes that accompany the evolution of this unique behavior had drawn relatively little attention (Smith, 1988;Schwenk and Bell, 1988;Herrel et al, 1995;Meyers and Nishikawa, 2000). Despite these numerous studies devoted to the hyobranchial system in iguanians, no consensus has been reached regarding the homology and, hence, the terminology of the elements of the hyobranchial apparatus or the associated hyobranchial musculature.…”

Using finite‐element analysis to investigate suture morphology: A case study using large carnivorous dinosaurs

“…Caution must be exercised, however, when predicting mobility at such contacts as in vivo evidence documents cases where movement is not observed despite morphology permitting mobility, e.g., morphology of the basal unit in nonmesokinetic iguanids and teiids (Throckmorton, 1976;Smith, 1980;Smith and Hylander, 1985;Herrel et al, 1995;. Furthermore, although an individual suture may appear potentially mobile, linked elements and consequent restrictions on their movements must be considered, as they often severely impair flexibility at adjacent joints.…”

The cranial morphometrics of the wildfowl (Anatidae)

“…In anatids as well the cranial and bill characters are related to bite force and the reaction forces in the joints with the upper bill (Herrel et al 1995). It is uncertain if the ligaments and the quadrate bone are responsible for the mobility.…”