Comparison of wildlife and captivity rattlesnakes (Crotalus durissus terrificus) microbiota

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

The thermogenesis of digestion in rattlesnakes

Some snakes have a feeding regime characterized by the infrequent ingestion of relatively large meals, causing impressive increments in post-prandial metabolism. Metabolism remains elevated for many days, while digestion proceeds, resulting in considerable investment of time and energy. Snakes actively adjust thermoregulatory behavior to raise their body temperature during digestion, exhibiting a post-prandial thermophilic response that accelerates digestion at the expense of higher metabolic rates. In the present study, we investigated the possibility that endogenously derived heat, originating as a byproduct of the post-prandial increase in metabolism, could itself contribute to the elevated body temperature during digestion in the South American rattlesnake Crotalus durissus. We assessed heat production, at a constant environmental temperature, by taking infrared (IR) images of snakes during fasting and after being fed meals varying from 10% to 50% of their own body masses. Our results show clearly that digesting rattlesnakes have significantly increased body temperatures, even when precluded from adjusting their thermoregulatory behavior. The feeding-derived thermogenesis caused the surface body temperature of rattlesnakes to increase by 0.9-1.2degreesC, a temperature change that will significantly affect digestive performance. The alterations in body temperature following feeding correlated closely with the temporal profile of changes in post-prandial metabolism. Moreover, the magnitude of the thermogenesis was greater for snakes fed large meals, as was the corresponding metabolic response. Since IR imaging only assesses surface temperatures,, the magnitude of the thermogenesis and the changes in deep core temperature could be even more pronounced than is reported here.

Energetic cost of predation: Aerobic metabolism during prey ingestion by juvenile rattlesnakes, Crotalus durissus

We investigated the cost of prey ingestion in the South American rattlesnake, Crotalus durissus, to see if the capacity to generate energy aerobically could be a constraint on the size of the prey that can be ingested. To accomplish this goal, we measured time and aerobic metabolism (inferred from oxygen consumption) of juvenile C. durissus ingesting prey ranging from 10 to 50% of their own body mass. Time needed for prey ingestion increased with prey size, with prey representing 10 and 20% of snake size being ingested with the same effort. Whole animal rates of oxygen consumption increased linearly with prey size, but at a slower pace for snakes ingesting prey larger than 30% of their body mass. Aerobic factorial power input necessary for prey ingestion increased with prey size, and for snakes ingesting prey representing 50% of their body mass it equaled the aerobic factorial scope for exercise. For the maximum prey size tested, the aerobic derived energy necessary for prey ingestion represented 0.02% of the total energy content of the prey. Within the prey size range we studied, the cost of ingestion did not constitute any constraint on the size of the prey that can be ingested. These constraints are set by morphological (gape size), ecological (predation risk), and, probably, by physiological parameters, as suggested by the tendency of V̇O2 during ingestion to increase at a slower pace at relative larger prey sizes.

Description of three new species of Hepatozoon (Apicomplexa, Hepatozoidae) from Rattlesnakes (Crotalus durissus terrificus) based on molecular, morphometric and morphologic characters

Hepatozoon spp. are commonly found infecting snakes. Since the latter are parasitized by diverse forms and data in the literature show divergence, we studied Hepatozoon spp. diversity on Crotalus durissus terrificus snakes using both molecular and morphological approaches. Naturally infected animals were employed. Blood was collected, blood smears were prepared and an aliquot was stored at -20. °C for DNA extraction. Five specimens of C. durissus terrificus were selected, each of them infected with one gamont type. Morphological and morphometric analyses of the found gamonts led to their grouping into three populations. For molecular characterization, seven oligonucleotide pairs that amplify distinct regions of rDNA gene were tested by adopting the PCR technique. Only the oligonucleotide pairs HepF300/Hep900 and HEMO1/HEMO2 were efficient in amplifying and distinguishing different isolates of Hepatozoon spp. from snakes. The better results were obtained when both oligonucleotide pairs were used in association. Based on the molecular and morphologic differences, three new species were proposed: Hepatozoon cuestensis sp. nov.; Hepatozoon cevapii sp. nov. and Hepatozoon massardii sp. nov. This is the first description of new Hepatozoon species from snakes, based on molecular characterization and morphological data, in South America. © 2013 Elsevier Inc.

Evaporative respiratory cooling augments pit organ thermal detection in rattlesnakes

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

Assessing the influence of mechanical ventilation on blood gases and blood pressure in rattlesnakes

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

Systemic blood flow relations in conscious South American rattlesnakes

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

Venous tone and cardiac function in the South American rattlesnake Crotalus durissus: mean circulatory filling pressure during adrenergic stimulation in anaesthetised and fully recovered animals

The effects of adrenergic stimulation on mean circulatory filling pressure (MCFP), central venous pressure (P-CV) and stroke volume (Vs), as well as the effects of altered MCFP through changes of blood volume were investigated in rattlesnakes (Crotalus durissus). MCFP is an estimate of the upstream pressure driving blood towards the heart and is determined by blood volume and the activity of the smooth muscle cells in the veins (venous tone). MCFP can be determined as the plateau in P-CV during a total occlusion of blood flow from the heart.Vs decreased significantly when MCFP was lowered by reducing blood volume in anaesthetised snakes, whereas increased MCFP through infusion of blood (up to 3 ml kg(-1)) only led to a small rise in Vs. Thus, it seems that end-diastolic volume is not affected by an elevated MCFP in rattlesnakes. To investigate adrenergic regulation on venous tone, adrenaline as well as phenylephrine and isoproterenol (alpha- and beta-adrenergic agonists, respectively) were infused as bolus injections (2 and 10 mu g kg(-1)). Adrenaline and phenylephrine caused large increases in MCFP and P-CV, whereas isoproterenol decreased both parameters. This was also the case in fully recovered snakes. Therefore, adrenaline affects venous tone through both alpha- and beta-adrenergic receptors, but the alpha-adrenergic receptor dominates at the dosages used in the present study. Injection of the nitric oxide donor SNP caused a significant decrease in P-CV and MCFP. Thus, nitric oxide seems to affect venous tone.

Influência da temperatura corporal de cascavéis (Crotalus durissus) submetidas à anestesia com cetamina

O estudo objetivou verificar a influência da temperatura corporal nos parâmetros fisiológicos e nos períodos de indução e recuperação anestésicos de cascavéis (Crotalus durissus) anestesiadas com cetamina. Os animais foram previamente submetidos à hipotermia (HIPO) (<22°C) e normotermia (30°C) (NORMO) e anestesiados com 80mg/kg IM de cetamina. Foram avaliados os períodos de latência e recuperação da anestesia por meio do tônus de cabeça, tônus muscular e reflexo de endireitamento. Mensurou-se a frequência cardíaca (FC), tempo de apnéia e temperatura corporal em 0 min e 5, 10, 15, 30, 60, 90, 120 min e análise dos gases sanguíneos em 0 min, 30 e 60 min. Não houve diferença em relação ao período de latência entre os grupos. A recuperação dos animais em HIPO foi mais prolongada (5,5 horas) que em NORMO (3,5 horas). Obteve-se FC no grupo NORMO superior que no grupo HIPO. O tempo de apnéia manteve o mesmo padrão em ambos os grupos. em relação ao basal, tanto em HIPO quanto em NORMO o tempo de apnéia diminuiu acentuadamente entre 5 e 30 min. Observou-se acidose respiratória no grupo NORMO apenas em 0 min. O SvO2 elevou-se significativamente após 30 min, o mesmo ocorrendo com a PvO2. A PvCO2 diminuiu em ambos os grupos após 30 min. Evidenciou-se que a temperatura corporal influencia intrinsecamente o período de recuperação de cascavéis anestesiadas com cetamina.

Crystallization and preliminary X-ray diffraction analysis of crotoxin B from Crotalus durissus collilineatus venom

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

The ventilatory response to environmental hypercarbia in the South American rattlesnake, Crotalus durissus

To study the effects of environmental hypercarbia on ventilation in snakes, particularly the anomalous hyperpnea that is seen when CO(2) is removed from inspired gas mixtures (post-hypercapnic hyperpnea), gas mixtures of varying concentrations of CO(2) were administered to South American rattlesnakes, Crotalus durissus, breathing through an intact respiratory system or via a tracheal cannula by-passing the upper airways. Exposure to environmental hypercarbia at increasing levels, up to 7% CO(2), produced a progressive decrease in breathing frequency and increase in tidal volume. The net result was that total ventilation increased modestly, up to 5% CO(2) and then declined slightly on 7% CO(2). on return to breathing air there was an immediate but transient increase in breathing frequency and a further increase in tidal volume that produced a marked overshoot in ventilation. The magnitude of this post-hypercapnic hyperpnea was proportional to the level of previously inspired CO(2). Administration of CO(2) to the lungs alone produced effects that were identical to administration to both lungs and upper airways and this effect was removed by vagotomy. Administration of CO(2) to the upper airways alone was without effect. Systemic injection of boluses of CO(2)-rich blood produced an immediate increase in both breathing frequency and tidal volume. These data indicate that the post-hypercapnic hyperpnea resulted from the removal of inhibitory inputs from pulmonary receptors and suggest that while the ventilatory response to environmental hypercarbia in this species is a result of conflicting inputs from different receptor groups, this does not include input from upper airway receptors.

The role of nitric oxide in regulation of the cardiovascular system in reptiles

The roles that nitric oxide (NO) plays in the cardiovascular system of reptiles are reviewed, with particular emphasis on its effects on central vascular blood flows in the systemic and pulmonary circulations. New data is presented that describes the effects on hemodynamic variables in varanid lizards of exogenously administered NO via the nitric oxide donor sodium nitroprusside (SNP) and, preliminary data on the effects of SNP inhibition of nitric oxide synthase (NOS) by L-nitroarginine methyl ester (L-NAME). Furthermore. on hemodynamic variables in the tegu lizard are presented. The findings are compared with previously published data from Our laboratory on three other species of reptiles: pythons (Skovgaard, N., Galli, G., Taylor, E.W., Conlon, J.M., Wang.. T., 2005. Hemodynamic effects of python neuropeptide gamma in the anesthetized python, Python regius. Regul. Pept. 18, 15-26), rattlesnakes (Galli, G., Skovgaard, N., Abe, A.S., Taylor, E.W., Wang, T., 2005. The role of nitric oxide in the regulation of the systemic and the pulmonary vasculature of the rattlesnake, Crotalus durissus terrificus. J. Comp. Physiol. 175B, 201-208) and turtles (Crossley, D.A., Wang, T., Altimiras, J., 2000. Role of nitric oxide in the systemic and pulmonary circulation of anesthetized turtles (Trachemys scripta). J. Exp. Zool. 286, 683-689). These five species of reptiles possess different combinations of division of the heart and structural complexity of the lungs. Comparison of their responses to NO donors and NOS inhibitors may reveal whether the potential contribution of NO to vascular tone correlates with pulmonary complexity and/or with blood pressure. All existing studies oil reptiles have clearly established a potential role for NO in regulating vascular tone in the systemic circulation and NO may be important for maintaining basal systemic vascular tone in varanid lizards, pythons and turtles, through a continuous release of NO. In contrast., the pulmonary circulation is less responsive to NO donors or NOS inhibitors, and it was only in pythons and varanid lizards that the lungs responded to SNP. Both species have a functionally separated heart, so it is possible that NO may exert a larger role in species with low pulmonary blood pressures, irrespective of lung complexity. (C) 2005 Elsevier B.V. All rights reserved.

Diet of the rattlesnake Crotalus durissus in southeastern Brazil (Serpentes, Viperidae)

Gut contents of 633 live rattlesnakes from southeastern Brazil received at the Instituto Butantanitute, SP, Brazil between 1993 and 1995 were studied. The snakes were weighed, measured and sexed. Two hundred and fifty-nine rattlesnakes had stomach and/or intestinal contents. Prey size was estimated by comparison of prey items with specimens from museum collections. Rodents and small marsupials were the main prey eaten by the rattlesnakes, and only 1% of the items were found in the stomach, whereas 41% of the individuals in the sample had feces in the intestine. There was low correlation between size of snake and prey size. No seasonal difference in frequency was found between fed and not fed males, but the occurrence of fed females was significantly lower during summer than winter months (28.9% and 51.8%, respectively). Fed newborn rattlesnakes had the lowest frequency, and also fed on rodents.

Arterial acid-base status during digestion and following vascular infusion of NaHCO3 and HCl in the South American rattlesnake, Crotalus durissus

Digestion is associated with gastric secretion that leads to an alkalinisation of the blood, termed the alkaline tide. Numerous studies on different reptiles and amphibians show that while plasma bicarbonate concentration ([HCO3-](pl)) increases substantially during digestion, arterial pH (pHa) remains virtually unchanged, due to a concurrent rise in arterial PCO2 (PaCO2) caused by a relative hypoventilation. This has led to the suggestion that postprandial amphibians and reptiles regulate pHa rather than PaCO2.Here we characterize blood gases in the South American rattlesnake (Crotalus durissus) during digestion and following systemic infusions of NaHCO3 and HCl in fasting animals to induce a metabolic alkalosis or acidosis in fasting animals. The magnitude of these acid-base disturbances were similar in magnitude to that mediated by digestion and exercise. Plasma [HCOT] increased from 18.4+/-1.5 to 23.7+/-1.0 mmol L-1 during digestion and was accompanied by a respiratory compensation where PaCO2 increased from 13.0+/-0.7 to 19.1+/-1.4 mm Hg at 24 h. As a result, pHa decreased slightly, but were significantly below fasting levels 36 h into digestion. Infusion of NaHCO3 (7 mmol kg(-1)) resulted in a 10 mmol L-1 increase in plasma [HCO3-] within 1 h and was accompanied by a rapid elevation of pHa (from 7.58+/-0.01 to 7.78+/-0.02). PaCO2, however, did not change following HCO3- infusion, which indicates a lack of respiratory compensation. Following infusion of HCl (4 mmol kg(-1)), plasma pHa decreased by 0.07 units and [HCO3-](pl) was reduced by 4.6 mmol L-1 within the first 3 h. PaCO2, however, was not affected and there was no evidence for respiratory compensation.Our data show that digesting rattlesnakes exhibit respiratory compensations to the alkaline tide, whereas artificially induced metabolic acid-base disturbances of same magnitude remain uncompensated. It seems difficult to envision that the central and peripheral chemoreceptors would experience different stimuli during these conditions. One explanation for the different ventilatory responses could be that digestion induces a more relaxed state with low responsiveness to ventilatory stimuli. (C) 2005 Elsevier B.V. All rights reserved.