The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
William G. Ryerson - One of the best experts on this subject based on the ideXlab platform.
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Buccal Pumping mechanics of Xenopus laevis tadpoles: effects of biotic and abiotic factors.
The Journal of Experimental Biology, 2010Co-Authors: William G. Ryerson, Stephen M. DebanAbstract:Biotic factors such as body size and shape have long been known to influence kinematics in vertebrates. Movement in aquatic organisms can also be strongly affected by abiotic factors such as the viscosity of the medium. We examined the effects of both biotic factors and abiotic factors on Buccal Pumping kinematics in Xenopus tadpoles using high-speed imaging of an ontogenetic series of tadpoles combined with experimental manipulation of the medium over a 10-fold range of viscosity. We found influences of both biotic and abiotic factors on tadpole movements; absolute velocities and excursions of the jaws and hyoid were greater in higher viscosity fluid but durations of movements were unaffected. Smaller tadpoles have relatively wider heads and more robust hyoid muscles used in Buccal expansion and compression. Lever arm ratios were found to be constant at all sizes; therefore, smaller tadpoles have relatively higher resolved muscle forces and, like tadpoles in more viscous medium, displayed higher absolute velocities of jaw and hyoid movements. Nonetheless, small tadpoles drew in water at lower Reynolds numbers ( Re ) than predicted by kinematics, due to negative allometry of the Buccal pump. Finally, tadpoles transitioned from a flow regime dominated by viscous forces ( Re =2) to an intermediate regime ( Re =106).
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The r ole of abiotic and biotic factors in suspension feeding mechanics of Xenopus tadpoles
2008Co-Authors: William G. RyersonAbstract:As a comparison to the suction feeding mechanics in aquatic environments, I investigated Buccal Pumping in an ontogenetic series of suspension feeding Xenopus laevis tadpoles (4-18 mm snout-vent length) by examining the morphology, kinematics, fluid flow, pressure generated in the Buccal cavity, and effects of viscosity manipulation. Investigation of the dimensions of the feeding apparatus of Xenopus revealed that the feeding muscles exhibited strong negative allometry, indicating that larger tadpoles had relatively smaller muscles, while the mechanical advantage of those muscles did not change across the size range examined. Buccal volume and head width also exhibited negative allometry: smaller tadpoles had relatively wider heads and larger volumes. Tadpoles were imaged during Buccal Pumping to obtain kinematics of jaw and hyoid movements as well as fluid velocity. Scaling patterns were inconsistent with models of geometric growth, which predict that durations of movements are proportional to body length. Only scaling of maximum hyoid distance, duration of mouth closing, and duration of hyoid elevation could not be distinguished from isometry. The only negatively allometric variable was maximum gape distance. No effect of size was found for duration
E W Taylor - One of the best experts on this subject based on the ideXlab platform.
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Evidence of a functional role in lung inflation for the Buccal pump in the agamid lizard, Uromastyx aegyptius microlepis.
The Journal of experimental biology, 2001Co-Authors: M S Al-ghamdi, J F Jones, E W TaylorAbstract:This study has demonstrated that the agamid desert lizard Uromastyx aegyptius microlepis ventilates its lungs both with a triphasic, thoracic aspiratory pump and by gulping air, using a Buccal pump. These two mechanisms never occur simultaneously because bouts of Buccal Pumping are always initiated after the passive expiration that terminates a thoracic breath. Lung inflation arising from thoracic and Buccal ventilation was confirmed by direct recording of volume changes using a whole-body plethysmograph. This observation was further confirmed by mechanical separation of the inflationary pressures associated with these two breathing mechanisms, enabling the effects of lung inflation on Buccal breathing to be observed. This revealed that the Buccal pump is influenced by a powerful Hering-Breuer-type reflex, further confirming its role in lung inflation. Bilateral thoracic vagotomy tended to increase the variance of the amplitude and duration of the breaths associated with the aspiration pump and abolished the effects of lung inflation on the Buccal pump. Uromastyx has vagal afferents from pulmonary receptors that respond to changes in lung volume and appear not to be sensitive to CO2. This study describes two lung-inflation mechanisms (an amphibian-like Buccal pump and a mammalian-like aspiration pump) in a single extant amniote, both of which are subject to vagal feedback control.
Stephen M. Deban - One of the best experts on this subject based on the ideXlab platform.
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Buccal Pumping mechanics of Xenopus laevis tadpoles: effects of biotic and abiotic factors.
The Journal of Experimental Biology, 2010Co-Authors: William G. Ryerson, Stephen M. DebanAbstract:Biotic factors such as body size and shape have long been known to influence kinematics in vertebrates. Movement in aquatic organisms can also be strongly affected by abiotic factors such as the viscosity of the medium. We examined the effects of both biotic factors and abiotic factors on Buccal Pumping kinematics in Xenopus tadpoles using high-speed imaging of an ontogenetic series of tadpoles combined with experimental manipulation of the medium over a 10-fold range of viscosity. We found influences of both biotic and abiotic factors on tadpole movements; absolute velocities and excursions of the jaws and hyoid were greater in higher viscosity fluid but durations of movements were unaffected. Smaller tadpoles have relatively wider heads and more robust hyoid muscles used in Buccal expansion and compression. Lever arm ratios were found to be constant at all sizes; therefore, smaller tadpoles have relatively higher resolved muscle forces and, like tadpoles in more viscous medium, displayed higher absolute velocities of jaw and hyoid movements. Nonetheless, small tadpoles drew in water at lower Reynolds numbers ( Re ) than predicted by kinematics, due to negative allometry of the Buccal pump. Finally, tadpoles transitioned from a flow regime dominated by viscous forces ( Re =2) to an intermediate regime ( Re =106).
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Mechanism of Defensive Inflation in the Chuckwalla, Sauromalus obesus
Journal of Experimental Zoology, 1994Co-Authors: Stephen M. Deban, James C. O'reilly, Tad C. TheimerAbstract:The chuckwalla, Sauromalus obesus, avoids predation by wedging itself in a rock crevice and inflating its lungs beyond their normal inspiratory volume. Buccal and pulmonary pressures were recorded in S. obesus during defensive inflation and wedging. Maximum pulmo- nary pressure generated during defensive wedging was significantly higher and was achieved faster than that of nonwedging inflation. During inflation and wedging, S. obesus forces air into the lungs by pulsatile contraction of the Buccal cavity. Buccal pulse Pumping is an ancestral venti- lation behavior of vertebrates that S. obesus uses for defensive inflation. @ 1994 Wiley-Liss, Inc. Defensive inflation has been observed in at least 19 species of lizards, 25 species of snakes and two species of crocodilians (Greene, '88). Despite this widespread occurrence, few studies have examined mechanisms of inflation. Here we report results of our studies of the chuckwalla, Sauromalus obesus (Iguanidae), a species that can inflate its lungs to four times their normal inspiratory vol- ume (Salt, '43). Chuckwallas exhibit this inflation ability in a variety of social and defensive con- texts. Lung inflation occurs during intraspecific assertion, aggression and challenge displays (Berry, '74) and defensively in response to the odors of snake predators (Prieto and Sorenson, '75). During predator-avoidance behavior, the chuckwalla flees into a narrow rock crevice and inflates its lungs to wedge itself in place (Stebbins, '85; Berry, '74). The chuckwalla exhibits Buccal Pumping dur- ing inflation, suggesting that it fills its lungs us- ing a method other than aspiration, the normal mode of breathing in reptiles. During aspiration, air is drawn into the lungs by subatmospheric pressures generated in the expanding thoracic cav- ity (Carrier, '89; Gans and Clark, '78) and no throat oscillation is required. The rhythmic oscil- lations of the throat seen during inflation have led previous investigators to describe the mecha- nism of inflation in Sauromalus obesus as "air swallowing" (Salt, '43) or "deglutition" (Templeton, '64). Salt ('43) proposed that air is forced down the trachea with the tongue, and Templeton ('64)
Edwin W. Taylor - One of the best experts on this subject based on the ideXlab platform.
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Effects of temperature and hypercapnia on ventilation and breathing pattern in the lizard Uromastyx aegyptius microlepis.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2002Co-Authors: Wilfried Klein, Denis V. Andrade, Tobias Wang, Edwin W. TaylorAbstract:In most reptiles, the ventilatory response to hypercapnia consists of large increases in tidal volume (V(T)), whereas the effects on breathing frequency (f(R)) are more variable. The increased V(T) seems to arise from direct inhibition of pulmonary stretch receptors. Most reptiles also exhibit a transitory increase in ventilation upon removal of CO(2) and this post-hypercapnic hyperpnea may consist of changes in both V(T) and f(R). While it is well established that increased body temperature augments the ventilatory response to hypercapnia, the effects of temperature on the post-hypercapnic hyperpnea is less described. In the present study, we characterise the ventilatory response of the agamid lizard Uromastyx aegyptius to hypercapnia and upon the return to air at 25 and 35 degrees C. At both temperatures, hypercapnia caused large increases in V(T) and small reductions in f(R), that were most pronounced at the higher temperature. The post-hypercapnic hyperpnea, which mainly consisted of increased f(R), was numerically larger at 35 compared to 25 degrees C. However, when expressed as a proportion of the levels of ventilation reached during steady-state hypercapnia, the post-hypercapnic hyperpnea was largest at 25 degrees C. Some individuals exhibited Buccal Pumping where each expiratory thoracic breath was followed by numerous small forced inhalations caused by contractions of the Buccal cavity. This breathing pattern was most pronounced during severe hypercapnia and particularly evident during the post-hypercapnic hyperpnea.
R Wassersug - One of the best experts on this subject based on the ideXlab platform.
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Swimming kinematics and respiratory behaviour of Xenopus laevis larvae raised in altered gravity.
The Journal of experimental biology, 1998Co-Authors: M Fejtek, K Souza, A Neff, R WassersugAbstract:We examined the respiratory behaviours and swimming kinematics of Xenopus laevis tadpoles hatched in microgravity (Space Shuttle), simulated microgravity (clinostat) and hypergravity (3 g centrifuge). All observations were made in the normal 1 g environment. Previous research has shown that X. laevis raised in microgravity exhibit abnormalities in their lungs and vestibular system upon return to 1 g. The tadpoles raised in true microgravity exhibited a significantly lower tailbeat frequency than onboard 1 g centrifuge controls on the day of landing (day0), but this behaviour normalized within 9 days. The two groups did not differ significantly in Buccal Pumping rates. Altered buoyancy in the space-flight microgravity tadpoles was indicated by an increased swimming angle on the day after landing (day1). Tadpoles raised in simulated microgravity differed to a greater extent in swimming behaviours from their 1 g controls. The tadpoles raised in hypergravity showed no substantive effects on the development of swimming or respiratory behaviours, except swimming angle. Together, these results show that microgravity has a transient effect on the development of locomotion in X. laevis tadpoles, most notably on swimming angle, indicative of stunted lung development. On the basis of the behaviours we studied, there is no indication of neuromuscular retardation in amphibians associated with embryogenesis in microgravity.
