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PubMedDate not supplied

Experimental study of induced inflammation in the Brazilian Boa (Boa constrictor constrictor).

The objective of this work was to identify the cellular types present in inflammatory processes in the Brazilian snake, Boa constrictor constrictor. Blood smears were first made from three normal snakes and stained by several methods to identify the cell types present, thus facilitating the identification of cells in inflammatory processes induced in 16 further snakes by the subcutaneous implantation of cotton suture threads and circular coverslips. Implanted threads induced migration of heterophils and monocytes after 4 h, more intense monocyte migration after 24 h, an intense granulocytic migration inside and around the thread after 48 h, heterophilic granulocytes, macrophages and giant cells after 7 days, and giant cells with a typical granuloma response and persistence of heterophilic cells after 15, 69 and 117 days. The cell population attached to the implanted coverslips after 4 h was composed of heterophils, thrombocytes, erythrocytes and macrophages; after 24 and 48 h heterophils predominated, and after 7 days heterophils, macrophages and giant cells predominated.

Animals↗
PubMed2001

Responses of python gastrointestinal regulatory peptides to feeding.

In the Burmese python (Python molurus), the rapid up-regulation of gastrointestinal (GI) function and morphology after feeding, and subsequent down-regulation on completing digestion, are expected to be mediated by GI hormones and neuropeptides. Hence, we examined postfeeding changes in plasma and tissue concentrations of 11 GI hormones and neuropeptides in the python. Circulating levels of cholecystokinin (CCK), glucose-dependent insulinotropic peptide (GIP), glucagon, and neurotensin increase by respective factors of 25-, 6-, 6-, and 3.3-fold within 24 h after feeding. In digesting pythons, the regulatory peptides neurotensin, somatostatin, motilin, and vasoactive intestinal peptide occur largely in the stomach, GIP and glucagon in the pancreas, and CCK and substance P in the small intestine. Tissue concentrations of CCK, GIP, and neurotensin decline with feeding. Tissue distributions and molecular forms (as determined by gel-permeation chromatography) of many python GI peptides are similar or identical to those of their mammalian counterparts. The postfeeding release of GI peptides from tissues, and their concurrent rise in plasma concentrations, suggests that they play a role in regulating python-digestive responses. These large postfeeding responses, and similarities of peptide structure with mammals, make pythons an attractive model for studying GI peptides.

Animals↗
PubMedDate not supplied

Evolution of regulatory responses to feeding in snakes.

Do animal species that normally consume large meals at long intervals evolve to down-regulate their metabolic physiology while fasting and to up-regulate it steeply on feeding? To test this hypothesis, we compared postfeeding regulatory responses in eight snake species: four frequent feeders on small meals and four infrequent feeders on large meals. For each species, we measured factorial changes in metabolic rate, in activities and capacities of five small intestinal brush border nutrient transporters, and in masses of eight organs that function in nutrient processing after consumption of a rodent meal equivalent to 25% of the snake's body mass. It turned out that, compared with frequent feeders, infrequent feeders digest that meal more slowly; have lower metabolic rates, organ masses, and nutrient uptake rates and capacities while fasting; have higher energy expenditure during digestion; and have higher postfeeding factorial increases in metabolic rate, organ masses, and nutrient uptake rates and capacities. These conclusions, which conform to the hypothesis mentioned above, remain after phylogeny has been taken into account. The small organ masses and low nutrient transporter activities during fasting contribute to the low fasting metabolism of infrequent feeders. Quantitative calculations of partial energy budgets suggest that energy savings drive the evolution of low mass and activities of organs during fasting and of large postfeeding regulatory responses in infrequent feeders. We propose further tests of this hypothesis among other snake species and among other ectotherms.

Animals↗
PubMedDate not supplied

The effects of fasting duration on the metabolic response to feeding in Python molurus: an evaluation of the energetic costs associated with gastrointestinal growth and upregulation.

The oxygen uptake of Python molurus increases enormously following feeding, and the elevated metabolism coincides with rapid growth of the gastrointestinal organs. There are opposing views regarding the energetic costs of the gastrointestinal hypertrophy, and this study concerns the metabolic response to feeding after fasting periods of different duration. Since mass and function of the gastrointestinal organs remain elevated for several days after feeding, the metabolic increment following a second meal given soon after the first can reveal whether the metabolic costs relate to the upregulation of gastrointestinal organs or merely the metabolic cost of processing a meal. Eight juvenile pythons were kept on a regular feeding regime for 6 mo after hatching. At the beginning of the metabolic measurements, they were fed mice (20% of body mass), and the metabolic response to similarly sized meals was determined following 3, 5, 7, 14, 21, 30, and 60 d of fasting. Our data show that the metabolic response following feeding was large, ranging from 21% to 35% of ingested energy (mean=27%), but the metabolic response seems independent of fasting duration. Hence, the extraordinarily large cost of digestion in P. molurus does not appear to correlate with increased function and growth of gastrointestinal organs but must be associated with other physiological processes.

Animals↗
PubMedDate not supplied

Temperature and meal size effects on the postprandial metabolism and energetics in a boid snake.

We investigated the combined effect of meal size and temperature on the aerobic metabolism and energetics of digestion in Boa constrictor amarali. Oxygen uptake rates (Vd2;o2) and the duration of the digestion were determined in snakes fed with meals equaling to 5%, 10%, 20%, and 40% of the snake's body mass at 25 degrees and 30 degrees C. The maximum Vd2;o2 values attained during digestion were greater at 30 degrees C than at 25 degrees C. Both maximal Vd2;o2 values and the duration of the specific dynamic action (SDA) were attained sooner at 30 degrees C than at 25 degrees C. Therefore, the temperature effect on digestion in Boa is characterized by the shortening of the SDA duration at the expense of increased Vd2;o2. Energy allocated to SDA was not affected by meal size but was greater at 25 degrees C compared to 30 degrees C. This indicates that a postprandial thermophilic response can be advantageous not only by decreasing the duration of digestion but also by improving digestive efficiency. Maximal Vd2;o2 and SDA duration increased with meal size at both temperatures.

Adaptation, Physiological↗
PubMed2005

The effect of meal composition on specific dynamic action in burmese pythons (Python molurus).

We quantified the specific dynamic action (SDA) resulting from the ingestion of various meal types in Burmese pythons (Python molurus) at 30 degrees C. Each snake was fed a series of experimental meals consisting of amino acid mixtures, simple proteins, simple or complex carbohydrates, or lipids as well as meals of whole animal tissue (chicken breast, beef suet, and mouse). Rates of oxygen consumption were measured for approximately 4 d after feeding, and the increment above standard metabolic rate was determined and compared to energy content of the meals. While food type (protein, carbohydrate, and lipid) had a general influence, SDA was highly dependent on meal composition (i.e., amino acid composition and carbohydrate structure). For chicken breast and simple carbohydrates, the SDA coefficient was approximately one-third the energetic content of the meal. Lard, suet, cellulose, and starch were not digested and did not produce measurable SDA. We conclude that the cost of de novo protein synthesis is an important component of SDA after ingestion of protein meals because (1) simple proteins, such as gelatin and collagen, did not stimulate levels of SDA attained after consumption of complete protein, (2) incomplete mixtures of amino acids failed to elicit the SDA of a complete mixture, and (3) the inhibition of de novo protein synthesis with the drug cycloheximide caused a more than 70% decrease in SDA. Stomach distension and mechanical digestion of intact prey did not cause measurable SDA.

Amino Acids↗
PubMed2006

Using direct calorimetry to test the accuracy of indirect calorimetry in an ectotherm.

We previously demonstrated that the relationship between respiratory gas exchange and metabolic heat production is unexpectedly variable and that conventional approaches to estimating energy expenditure by indirect calorimetry can incorporate large errors. Prior studies, however, comparing direct and indirect calorimetry of animals focused only on endothermic organisms. Given that endothermy and ectothermy represent a fundamental dichotomy of animal energetics, in this analysis we explore how these contrasting physiologies correlate with the relationship between heat production and respiratory gas exchange. Simultaneous indirect and direct calorimetry in an ectotherm, the ball python (Python regius Shaw), revealed that the relationships between gas exchange and heat production were within 1% of those expected when analyses using indirect calorimetry were based on the assumption that the fasting animal catabolized only protein. This accuracy of indirect calorimetry contrasts sharply with our previous conclusions for three species of birds and mammals.

Animals↗
PubMedDate not supplied

Determinants of the postfeeding metabolic response of Burmese pythons, Python molurus.

The relatively large meal sizes consumed by sit-and-wait-foraging snake species make them favorable for investigating specific dynamic action, the rise in metabolic rate associated with digestion. Hence, we measured O2 consumption rates (VO2) before and up to 20 d after Burmese pythons (Python molurus) either had only constricted and killed rodent meals or had also been allowed to consume meals ranging in size from 5% to 111% of their body mass. Postprandial VO2 peaked within 2 d at a value that increased with meal size, up to 44 times standard metabolic rate for the largest meals. In addition to being the largest known magnitude of postprandial metabolic response, this also exceeds the factorial increase in VO2 during peak physical activity for all studied animals except perhaps racehorses. Specific dynamic action, calculated from the extra VO2 above standard metabolic rate over the duration of digestion, increased with meal size and equaled 32% of ingested meal energy. The allometric exponent for body mass was 0.68 for standard metabolic rate, 0.90 for peak postprandial VO2, and 1.01 for specific dynamic action. Specific dynamic action is higher, and standard metabolic rate is lower, in sit-and-wait-foraging snake species than in actively foraging snake species. This suggests that sit-and-wait-foraging snakes, which consume large meals at long and unpredictable intervals, reduce standard metabolic rate by allowing the energetically expensive small intestine and other associated organs to atrophy between meals but thereby incur a large specific dynamic action while rebuilding those organs upon feeding.

Animals↗
PubMedDate not supplied

The thermal biology of digestion in rubber boas (Charina bottae): physiology, behavior, and environmental constraints.

Coadaptation predicts a match between the thermal physiology and thermoregulatory behavior of reptiles. We tested this prediction by studying the digestive biology of rubber boas (Charina bottae). We measured the thermal dependence of gastric digestive rate and passage rate in rubber boas from 10 degrees C to 35 degrees C. We examined the effect of digestion on their thermal preference by measuring the temperatures of C. bottae in a thermal gradient before and after feeding. While the passage rates calculated from the body temperatures of digesting snakes were higher than the passage rates calculated from the body temperatures of nondigesting snakes, there was no difference in calculated digestive rates. These results indicate that the thermoregulatory behavior of C. bottae may be more tightly correlated with factors affecting passage rate than with digestive rate alone. Results of simulating the constraints of the thermal environment on the digestive biology of C. bottae showed that digestion would take more than twice as long in the spring as in the summer. In addition, during the summer, snakes thermoregulating as digesting snakes would pass food 12% faster than those thermoregulating as nondigesting snakes. These results demonstrate how interpretation of laboratory studies can be improved when combined with measurements of appropriate environmental conditions.

Animals↗
PubMedDate not supplied

Tolerance of snakes to hypergravity.

Sensitivity of carotid blood flow to increased gravitational force acting in the head-to-tail direction(+Gz) was studied in diverse species of snakes hypothesized to show adaptive variation of response. Tolerance to increased gravity was measured red as the maximum graded acceleration force at which carotid blood flow ceased and was shown to vary according to gravitational adaptation of species defined by their ecology and behavior. Multiple regression analysis showed that gravitational habitat, but not body length, had a significant effect on Gz tolerance. At the extremes, carotid blood flow decreased in response to increasing G force and approached zero near +1 Gz in aquatic and ground-dwelling species, whereas in climbing species carotid flow was maintained at forces in excess of +2 Gz. Tolerant (arboreal) species were able to withstand hypergravic forces of +2 to +3 Gz for periods up to 1 h without cessation of carotid blood flow or loss of body movement and tongue flicking. Data suggest that the relatively tight skin characteristic of tolerant species provides a natural antigravity suit and is of prime importance in counteracting Gz stress on blood circulation.

Acceleration↗
PubMed2004

Pythons metabolize prey to fuel the response to feeding.

We investigated the energy source fuelling the post-feeding metabolic upregulation (specific dynamic action, SDA) in pythons (Python regius). Our goal was to distinguish between two alternatives: (i) snakes fuel SDA by metabolizing energy depots from their tissues; or (ii) snakes fuel SDA by metabolizing their prey. To characterize the postprandial response of pythons we used transcutaneous ultrasonography to measure organ-size changes and respirometry to record oxygen consumption. To discriminate unequivocally between the two hypotheses, we enriched mice (= prey) with the stable isotope of carbon (13C). For two weeks after feeding we quantified the CO2 exhaled by pythons and determined its isotopic 13C/12C signature. Ultrasonography and respirometry showed typical postprandial responses in pythons. After feeding, the isotope ratio of the exhaled breath changed rapidly to values that characterized enriched mouse tissue, followed by a very slow change towards less enriched values over a period of two weeks after feeding. We conclude that pythons metabolize their prey to fuel SDA. The slowly declining delta13C values indicate that less enriched tissues (bone, cartilage and collagen) from the mouse become available after several days of digestion.

Analysis of Variance↗
PubMed2004

A parvovirus isolated from royal python (Python regius) is a member of the genus Dependovirus.

Parvoviruses were isolated from Python regius and Boa constrictor snakes and propagated in viper heart (VH-2) and iguana heart (IgH-2) cells. The full-length genome of a snake parvovirus was cloned and both strands were sequenced. The organization of the 4432-nt-long genome was found to be typical of parvoviruses. This genome was flanked by inverted terminal repeats (ITRs) of 154 nt, containing 122 nt terminal hairpins and contained two large open reading frames, encoding the non-structural and structural proteins. Genes of this new parvovirus were most similar to those from waterfowl parvoviruses and from adeno-associated viruses (AAVs), albeit to a relatively low degree and with some organizational differences. The structure of its ITRs also closely resembled those of AAVs. Based on these data, we propose to classify this virus, the first serpentine parvovirus to be identified, as serpentine adeno-associated virus (SAAV) in the genus Dependovirus.

Amino Acid Sequence↗
PubMed2005

Paternal alleles enhance female reproductive success in tropical pythons.

The conventional view that female reproductive success is unlikely to benefit from multiple mating has come under strong challenge in recent years. In the present study, we demonstrate that the time wild-caught reproductive female water pythons (Liasis fuscus) spent in the laboratory prior to oviposition affected both hatching success and the number of male microsatellite alleles detected in the broods. A negative correlation between time in captivity and number of male alleles observed in the broods suggests that reduced hatching success was most likely not caused by environmental factors such as non-optimal temperatures, but rather by restricted mating opportunities. Maternal nutritional status and mean hatchling mass did not affect brood viability. However, our results revealed a positive correlation between number of male microsatellite alleles observed in the broods and hatching success, suggesting that increased paternal genetic variability enhanced female reproductive success. As microsatellite loci are unlikely to be direct targets of selection, we suggest that variability at these loci may cosegregate with other polymorphic genes directly linked to fitness.

Alleles↗
PubMed2006

MHC class I variation associates with parasite resistance and longevity in tropical pythons.

Using restriction fragment length polymorphism (RFLP) we identified 26 unique major histocompatibility complex (MHC) genotypes in 104 water pythons. We observed a significant independent association between reduced blood parasite load (Hepatozoon sp.) and python body length/age, presence of a specific RFLP fragment (C-fragment) and the overall number of fragments. The parasite has a negative impact on several python life-history traits such as growth, nutritional status and longevity. Thus, the C-fragment could be considered a 'good gene' (a fitness-enhancing genetic element). However, while the number of fragments affected parasite load, the association between level of parasitaemia and fragment number was not linear, and, hence, minimum parasite infection level was achieved at an intermediate number of fragments. Intermediate MHC fragment numbers were also observed among the largest/oldest pythons, suggesting that both a specific fragment and intermediate levels of MHC polymorphism enhanced python longevity. Thus, our results suggest python MHC is subject to both frequency-dependent and balancing selection.

Animals↗
PubMed2005

An ecological risk assessment of nonnative boas and pythons as potentially invasive species in the United States.

The growing international trade in live wildlife has the potential to result in continuing establishment of nonnative animal populations in the United States. Snakes may pose particularly high risks as potentially invasive species, as exemplified by the decimation of Guam's vertebrate fauna by the accidentally introduced brown tree snake. Herein, ecological and commercial predictors of the likelihood of establishment of invasive populations were used to model risk associated with legal commercial imports of 23 species of boas, pythons, and relatives into the United States during the period 1989-2000. Data on ecological variables were collected from multiple sources, while data on commercial variables were collated from import records maintained by the U.S. Fish and Wildlife Service. Results of the risk-assessment models indicate that species including boa constrictors (Boa constrictor), ball pythons (Python regius), and reticulated pythons (P. reticulatus) may pose particularly high risks as potentially invasive species. Recommendations for reducing risk of establishment of invasive populations of snakes and/or pathogens include temporary quarantine of imports to increase detection rates of nonnative pathogens, increasing research attention to reptile pathogens, reducing the risk that nonnative snakes will reach certain areas with high numbers of federally listed species (such as the Florida Keys), and attempting to better educate individuals purchasing reptiles.

Animals↗