Developing a Writing-Intensive Course in Animal Physiology

The project details how Comparative Animal Physiology, a two-semester upper division biology elective, is transformed to meet writing-intensive discipline-appropriate criteria. Targeted and scaffolded assignments allow students to write about physiology in a variety of styles, and to help revise each other’s work to better understand the iterative process of writing. Assignments are aligned with WI student learning outcomes, to promote critical, reflective and effective communication skills

Electromyographic pattern of the gular pump in monitor lizards

Journal ArticleGular pumping in monitor lizards is known to play an important role in lung ventilation, but its evolutionary origin has not yet been addressed. To determine whether the gular pump derives from the buccal pump of basal tetrapods or is a novel invention, we investigated the electromyographic activity associated with gular pumping in savannah monitor lizards (Varanus exanthematicus). Electrodes were implanted in hyobranchial muscles, and their activity patterns were recorded synchronously with hyoid kinematics, respiratory airflow, and gular pressure. Movement of the highly mobile hyoid apparatus effects large-volume airflows in and out of the gular cavity. The sternohyoideus and branchiohyoideus depress, retract, and abduct the hyoid, thus expanding the gular cavity. The omohyoideus, constrictor colli, intermandibularis, and mandibulohyoideus elevate, protract, and adduct the hyoid, thus compressing the gular cavity. Closure of the choanae by the sublingual plicae precedes gular compression, allowing positive pressure to be generated in the gular cavity to force air into the lungs. The gular pump of monitor lizards is found to exhibit a neuromotor pattern similar to the buccal pump of extant amphibians, and both mechanisms involve homologous muscles. This suggests that the gular pump may have been retained from the ancestral buccal pump. This hypothesis remains to be tested by a broad comparative analysis of gular pumping among the amniotes

The importance of the crocodilian hepatic piston pump to ventilation during altered respiratory demand

Crocodilians ventilate through a combination of the intercostal muscles, the abdominal muscles and the diaphragmaticus muscle. Previous studies report that the caudal-cranial movement of the liver during the ventilatory cycle by the diaphragmaticus muscle, termed the hepatic piston pump, is solely responsible for ventilation in floating caimans. However, the importance of the hepatic-piston pump to ventilation in crocodilians under altered conditions of ventilatory demand is unknown. The hepatic-piston pump made only a limited contribution to ventilation while crocodiles rested at 30OC, following a decrease in temperature (20OC, reduced ventilatory demand), and during hypercapnia (5% CO2, increased ventilatory drive). The diaphragmatic muscle was important for facilitating ventilation during exercise (increased ventilatory demand) as loss of the hepatic piston pump, following inactivation of the diaphragmaticus muscle, compromised exercise induced increases in tidal volume and minute ventilation. A relative hyperventilation was induced by exercise (both with and without a functional hepatic piston pump) and, as a result, the alterations in ventilation following inactivation of the diaphragmaticus muscle did not significantly alter arterial oxygenation

Exhaustive Exercise Training Enhances Aerobic Capacity in American Alligator (\u3ci\u3eAlligator Mississippiensis\u3c/i\u3e)

The oxygen transport system in mammals is extensively remodelled in response to repeated bouts of activity, but many reptiles appear to be ‘metabolically inflexible’ in response to exercise training. A recent report showed that estuarine crocodiles (Crocodylus porosus) increase their maximum metabolic rate in response to exhaustive treadmill training, and in the present study, we confirm this response in another crocodilian, American alligator (Alligator mississippiensis). We further specify the nature of the crocodilian training response by analysing effects of training on aerobic [citrate synthase (CS)] and anaerobic [lactate dehydrogenase (LDH)] enzyme activities in selected skeletal muscles, ventricular and skeletal muscle masses and haematocrit. Compared to sedentary control animals, alligators regularly trained for 15 months on a treadmill (run group) or in a flume (swim group) exhibited peak oxygen consumption rates higher by 27 and 16%, respectively. Run and swim exercise training significantly increased ventricular mass (~11%) and haematocrit (~11%), but not the mass of skeletal muscles. However, exercise training did not alter CS or LDH activities of skeletal muscles. Similar to mammals, alligators respond to exercise training by increasing convective oxygen transport mechanisms, specifically heart size (potentially greater stroke volume) and haematocrit (increased oxygen carrying-capacity of the blood). Unlike mammals, but similar to squamate reptiles, alligators do not also increase citrate synthase activity of the skeletal muscles in response to exercise

Isokinetic Muscle Strength and Fatigue Evaluation Following a Combined Aerobic and Resistance Training Program on a Gravity Independent Flywheel Device

Exposure to microgravity imposes changes on the musculoskeletal and cardiovascular systems leading to decreases in aerobic capacity, muscular strength, and muscular fatigue (1). Anti-gravity muscles, those that play a postural role in a standard gravity environment such as the soleus and quadriceps, are most affected by microgravity (2) with nearly all musculature affected with extended spaceflight (3). The multi-mode exercise device (M-MED) is a gravity independent device that provides both high force resistance type and low force aerobic type modes of exercise. Consequently, the M-MED has the ability to enhance both skeletal muscle function through resistance training exercises as well as cardiovascular function with aerobic training

Exhaustive exercise training enhances aerobic capacity in American alligator (Alligator mississippiensis)

The oxygen transport system in mammals is extensively remodelled in response to repeated bouts of activity, but many reptiles appear to be ‘metabolically inflexible’ in response to exercise training. A recent report showed that estuarine crocodiles (Crocodylus porosus) increase their maximum metabolic rate in response to exhaustive treadmill training, and in the present study, we confirm this response in another crocodilian, American alligator (Alligator mississippiensis). We further specify the nature of the crocodilian training response by analysing effects of training on aerobic [citrate synthase (CS)] and anaerobic [lactate dehydrogenase (LDH)] enzyme activities in selected skeletal muscles, ventricular and skeletal muscle masses and haematocrit. Compared to sedentary control animals, alligators regularly trained for 15 months on a treadmill (run group) or in a flume (swim group) exhibited peak oxygen consumption rates higher by 27 and 16%, respectively. Run and swim exercise training significantly increased ventricular mass (~11%) and haematocrit (~11%), but not the mass of skeletal muscles. However, exercise training did not alter CS or LDH activities of skeletal muscles. Similar to mammals, alligators respond to exercise training by increasing convective oxygen transport mechanisms, specifically heart size (potentially greater stroke volume) and haematocrit (increased oxygen carrying-capacity of the blood). Unlike mammals, but similar to squamate reptiles, alligators do not also increase citrate synthase activity of the skeletal muscles in response to exercise

Function of intracoelomic septa in lung ventilation of amniotes: Lessons from lizards

Aspiration breathing is the dominant mechanism of lung inflation among extant amniotes. However, aspiration has two fundamental problems associated with it: paradoxical visceral translation and partial lung collapse. These can constrain the inspiratory tidal volume, reduce the effective lung ventilation, and ultimately curtail the aerobic capacity of an animal. Separation of the pleural and peritoneal cavities by an intracoelomic septum can restrict the cranial shift of abdominal viscera and provide structural support to the caudal lung surface. A muscular septum, such as the diaphragm of mammals or the diaphragmaticus of crocodilians, can exert active control over visceral translation and the degree of lung inflation. To a lesser degree, a nonmuscular septum can also function as a passive barrier when stretched taut by rib rotation. Studies of the posthepatic septum in teiid lizards and the postpulmonary septum in varanid lizards underscore the importance of nonmuscular septa in aspiration. These septa provide plausible functional models that help us infer the evolution of mammalian and avian lung ventilatory systems, respectively.Wilfried Klein, Tomasz Owerkowic

Exercise training enhances aerobic capacity in juvenile estuarine crocodiles (Crocodylus porosus)

Copyright © 2008 Elsevier Inc. All rights reserved.Tomasz Owerkowicz and Russell V. Baudinettehttp://www.elsevier.com/wps/find/journaldescription.cws_home/525464/description#descriptio

Surgical Removal of Right-to-Left Cardiac Shunt in the American Alligator (\u3ci\u3eAlligator Mississippiensis\u3c/i\u3e) Causes Ventricular Enlargement But Does Not Alter Apnoea or Metabolism During Diving

Crocodilians have complete anatomical separation between the ventricles, similar to birds and mammals, but retain the dual aortic arch system found in all non-avian reptiles. This cardiac anatomy allows surgical modification that prevents right-to-left (R–L) cardiac shunt. A R–L shunt is a bypass of the pulmonary circulation and recirculation of oxygen-poor blood back to the systemic circulation and has often been observed during the frequent apnoeic periods of non-avian reptiles, particularly during diving in aquatic species. We eliminated R–L shunt in American alligators (Alligator mississippiensis) by surgically occluding the left aorta (LAo; arising from right ventricle) upstream and downstream of the foramen of Panizza (FoP), and we tested the hypotheses that this removal of R–L shunt would cause afterload-induced cardiac remodelling and adversely affect diving performance. Occlusion of the LAo both upstream and downstream of the FoP for ~21 months caused a doubling of RV pressure and significant ventricular enlargement (average ~65%) compared with age-matched, sham-operated animals. In a separate group of recovered, surgically altered alligators allowed to dive freely in a dive chamber at 23°C, occlusion of the LAo did not alter oxygen consumption or voluntary apnoeic periods relative to sham animals. While surgical removal of R–L shunt causes considerable changes in cardiac morphology similar to aortic banding in mammals, its removal does not affect the respiratory pattern or metabolism of alligators. It appears probable that the low metabolic rate of reptiles, rather than pulmonary circulatory bypass, allows for normal aerobic dives

Atmospheric oxygen level affects growth trajectory, cardiopulmonary allometry and metabolic rate in the American alligator (Alligator mississippiensis)

Recent palaeoatmospheric models suggest large-scale fluctuations in ambient oxygen level over the past 550 million years. To better understand how global hypoxia and hyperoxia might have affected the growth and physiology of contemporary vertebrates, we incubated eggs and raised hatchlings of the American alligator. Crocodilians are one of few vertebrate taxa that survived these global changes with distinctly conservative morphology. We maintained animals at 30°C under chronic hypoxia (12% O2), normoxia (21% O2) or hyperoxia (30% O2). At hatching, hypoxic animals were significantly smaller than their normoxic and hyperoxic siblings. Over the course of 3 months, post-hatching growth was fastest under hyperoxia and slowest under hypoxia. Hypoxia, but not hyperoxia, caused distinct scaling of major visceral organs–reduction of liver mass, enlargement of the heart and accelerated growth of lungs. When absorptive and post-absorptive metabolic rates were measured in juvenile alligators, the increase in oxygen consumption rate due to digestion/absorption of food was greatest in hyperoxic alligators and smallest in hypoxic ones. Hyperoxic alligators exhibited the lowest breathing rate and highest oxygen consumption per breath. We suggest that, despite compensatory cardiopulmonary remodelling, growth of hypoxic alligators is constrained by low atmospheric oxygen supply, which may limit their food utilisation capacity. Conversely, the combination of elevated metabolism and low cost of breathing in hyperoxic alligators allows for a greater proportion of metabolised energy to be available for growth. This suggests that growth and metabolic patterns of extinct vertebrates would have been significantly affected by changes in the atmospheric oxygen level