The unequal influences of the left and right vagi on the control of the heart and pulmonary artery in the rattlesnake, Crotalus durissus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Physiological importance of the coronary arterial blood supply to the rattlesnake heart

The reptilian heart consists of a thick inner spongy myocardium that derives its oxygen and nutrient supply directly from the blood within the ventricular cavity, which is surrounded by a thin outer compact layer supplied by coronary arteries. The functional importance of these coronary arteries remains unknown. In the present study we investigate the effects of permanent coronary artery occlusion in the South American rattlesnake (Crotalus durissus) on the ability to maintain heart rate and blood pressure at rest and during short term activity. We used colored silicone rubber (Microfil) to identify the coronary artery distribution and interarterial anastomoses. The coronary circulation was occluded and the snakes were then kept for 4 days at 30 degrees C. Microfil injections verified that virtually all coronary arteries had successfully been occluded, but also made visible an extensive coronary supply to the outer compact layer in untreated snakes. Electrocardiogram (ECG), blood pressure (P(sys)) and heart rate (f(H)) were measured at rest and during enforced activity at day 1 and 4. Four days after occlusion of the coronary circulation, the snakes could still maintain a P(sys) and f(H) of 5.2 +/- 0.2 kPa and 58.2 +/- 2.2 beats min(-1), respectively, during activity and the ECG was not affected. This was not different from sham-operated snakes. Thus, while the outer compact layer of the rattlesnake heart clearly has an extensive coronary supply, rattlesnakes sustain a high blood pressure and heart rate during activity without coronary artery blood supply.

Microhabitat use by species of the genera Bothrops and Crotalus (Viperidae) in semi-extensive captivity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Hypoxic pulmonary vasoconstriction in reptiles: a comparative study of four species with different lung structures and pulmonary blood pressures

Low O-2 levels in the lungs of birds and mammals cause constriction of the pulmonary vasculature that elevates resistance to pulmonary blood flow and increases pulmonary blood pressure. This hypoxic pulmonary vasoconstriction (HPV) diverts pulmonary blood flow from poorly ventilated and hypoxic areas of the lung to more well-ventilated parts and is considered important for the local matching of ventilation to blood perfusion. In the present study, the effects of acute hypoxia on pulmonary and systemic blood flows and pressures were measured in four species of anesthetized reptiles with diverse lung structures and heart morphologies: varanid lizards (Varanus exanthematicus), caimans (Caiman latirostris), rattlesnakes (Crotalus durissus), and tegu lizards (Tupinambis merianae). As previously shown in turtles, hypoxia causes a reversible constriction of the pulmonary vasculature in varanids and caimans, decreasing pulmonary vascular conductance by 37 and 31%, respectively. These three species possess complex multicameral lungs, and it is likely that HPV would aid to secure ventilation-perfusion homogeneity. There was no HPV in rattlesnakes, which have structurally simple lungs where local ventilation-perfusion inhomogeneities are less likely to occur. However, tegu lizards, which also have simple unicameral lungs, did exhibit HPV, decreasing pulmonary vascular conductance by 32%, albeit at a lower threshold than varanids and caimans (6.2 kPa oxygen in inspired air vs. 8.2 and 13.9 kPa, respectively). Although these observations suggest that HPV is more pronounced in species with complex lungs and functionally divided hearts, it is also clear that other components are involved.

Reproductive biology of the neotropical rattlesnake Crotalus durissus from northeastern Brazil: a test of phylogenetic conservatism of reproductive patterns

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Caracaterização ultrassonográfica, morfofisiológica do sistema reprodutor de machos e fêmeas de Crotalus durissus terrificus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influência do controle vagal na resistência vascular pulmonar e desvio intracardíaco em Crotalus durissus (Squamata: Viperidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Loss of the Ability to Control Right-to-Left Shunt Does Not Influence the Metabolic Responses to Temperature Change or Long-Term Fasting in the South American Rattlesnake Crotalus durissus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Does the rattle of Crotalus durissus terrificus reveal its dietary history?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influência da temperatura e do termoperíodo sobre a taxa metabólica de repouso em cascavéis, Crotalus durissus (Serpentes: Viperidae)

Snakes are ectothermic animals and, therefore, their physiological functions are strongly affected by temperature. For instance, the resting metabolic rate (RMR) of this animals increase with the rise in body temperature. However, metabolic determinations in ectothermic organisms, including snakes, are generally made by submitting the animals to constant temperature regimes. This experimental procedure, although widely used, accepted and certainly suitable in several cases, submit the animals to a very different situation from that experienced by them in nature. In fact, ectothermics are known by presenting extensive variations in their body temperatures trough the day and/or seasons. If this disagreement between the thermal biology of the animals and the experimental conditions, for instance over the circadian cycle, affects the determinations of metabolic rates of ectotherm animals, remains quite uncertain. Thus, this study aimed to test the effects of different thermal regimes (fluctuating vs constant) in different temperature ranges over the TMR of rattlesnakes (Crotalus durissus). Therefore, the TMR of rattlesnakes was measured by the oxygen consumption rates ( V O2) in the constant temperatures of 15°C, 20°C, 25°C, 30°C and 35°C. For fluctuating regimes, snakes were measured in thermoperiods of 12/12 hours, as follows: 15°C and 25°C; 20°C and 30°C; 25°C and 35°C. Our results show that the RMR of C. durissus rises as the temperature increases, regardless of the thermal regime. The obtained RMR in the constant regimes of 20°C and 25°C was not different from that measured in the correspondent fluctuating regimes (i.e., 15 - 25°C e 20 - 30°C). However, at constant 30°C, the RMR was significantly higher than that obtained in the 30°C fluctuating regime (25 - 35ºC). This indicates that the potential effects in submitting of snakes to different thermal regimes of its thermal biology become more important with...