Luís Felipe Toledo

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 (V̇o2) 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° and 30°C. The maximum V̇o2 values attained during digestion were greater at 30°C than at 25°C. Both maximal V̇o2 values and the duration of the specific dynamic action (SDA) were attained sooner at 30°C than at 25°C. Therefore, the temperature effect on digestion in Boa is characterized by the shortening of the SDA duration at the expense of increased V̇o2. Energy allocated to SDA was not affected by meal size but was greater at 25°C compared to 30°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 V̇o2 and SDA duration increased with meal size at both temperatures.

Colors and Some Morphological Traits as Defensive Mechanisms in Anurans

Anurans may be brightly colored or completely cryptic. Generally, in the former situation, we are dealing with aposematism, and the latter is an example of camouflage. However, these are only simple views of what such colorations really mean and which defensive strategy is implied. For instance, a brightly colored frog may be part of a mimicry ring, which could be either Batesian, Mullerian, or Browerian. These are only examples of the diversity of color-usage systems as defensive strategies. Unfortunately, reports on the use of colors as defensive mechanisms are widespread in the available literature, and the possible functions are rarely mentioned. Therefore, we reviewed the literature and added new data to this subject. Then, we the use of colors (as defensive mechanism) into categories. Mimicry was divided into the subcategories camouflage, homotypy, and nondeceitful homotypy, and these groups were also subcategorized. Dissuasive coloration was divided into behavioral display of colors, polymorphism, and polyphenism. Aposematism was treated apart, but aposematic colorations may be present in other defensive strategies. Finally, we propose functions and forms of evolution for some color systems in post-metamorphic anurans and hope that this review can be the basis for future research, even on other animal groups.

Ventilatory compensation of the alkaline tide during digestion in the snake Boa constrictor

SUMMARY The increased metabolic rate during digestion is associated with changes in arterial acid–base parameters that are caused by gastric acid secretion (the `alkaline tide). Net transfer of HCl to the stomach lumen causes an increase in plasma HCO3– levels, but arterial pH does not change because of a ventilatory compensation that counters the metabolic alkalosis. It seems, therefore, that ventilation is controlled to preserve pH and not PCO2 during the postprandial period. To investigate this possibility, we determined arterial acid–base parameters and the metabolic response to digestion in the snake Boa constrictor, where gastric acid secretion was inhibited pharmacologically by oral administration of omeprazole. The increase in oxygen consumption of omeprazole-treated snakes after ingestion of 30% of their own body mass was quantitatively similar to the response in untreated snakes, although the peak of the metabolic response occurred later (36 h versus 24 h). Untreated control animals exhibited a large increase in arterial plasma HCO3– concentration of approximately 12 mmol l–1, but arterial pH only increased by 0.12 pH units because of a simultaneous increase in arterial PCO2 by about 10 mmHg. Omeprazole virtually abolished the changes in arterial pH and plasma HCO3– concentration during digestion and there was no increase in arterial PCO2. The increased arterial PCO2 during digestion is not caused, therefore, by the increased metabolism during digestion or a lower ventilatory responsiveness to ventilatory stimuli during a presumably relaxed state in digestion. Furthermore, the constant arterial PCO2, in the absence of an alkaline tide, of omeprazole-treated snakes strongly suggests that pH rather than PCO2 normally affects chemoreceptor activity and ventilatory drive.

Taxocenose de anuros de uma mata semidecídua do interior do Estado de São Paulo e comparações com outras taxocenoses do estado, sudeste do Brasil

The present study was conducted in a remnant of semi-deciduous forest, Mata Sao Jose (MSJ), and in its adjacent areas in the municipality of Rio Claro, state of Sao Paulo, Brazil. Information about anuran species richness and their spatial and temporal distribution were collected from August 2002 to July 2003. Most of the 24 registered species called and breed in open areas around the remnant. Only three species, Hypsiboas lundii, H. prasinus, and Proceratophrys boiei, used environments inside the fragment as reproductive sites and only H. prasinus used also environments around the remnant. The majority of the species were found during the rainy season and temporary environments were the most used for reproduction. The species composition of MSJ was compared with 10 other localities with the following vegetation composition: a preserved tropical rain forest, ecotone of tropical rain forest and semi-deciduous altered forest, preserved Cerrado, and disturbed areas (used as agriculture and pasture for cattle). The anuran composition of the MSJ and that from other semi-deciduous forest were more similar to the anuran composition of more perturbed areas and to the anuran composition of Cerrado then to the anuran composition of the rain forest habitats. There was no significant correlation between the distance of the areas and the similarity ratio of them. Proceratophrys boiei and H. lundii appear to be the species more affected by habitat fragmentation in the state of Sao Paulo due to their reproductive ecology and dependence of forested habitats.

Acoustic Repertoire and Calling Behavior of Scinax fuscomarginatus (Anura, Hylidae)

Abstract Vocalizations are important in anuran communication, especially during the breeding season. Calling affects spatial organization of males at breeding sites, promotes attraction of new individuals to the chorus, and attracts mature females for reproduction. We describe four distinct vocalizations (advertisement calls, sporadic calls, and two types of aggressive calls) emitted by adult males of Scinax fuscomarginatus. With the exception of the advertisement call, the remaining descriptions are novel. We also describe calling sites, calling season, and nightly calling activity. Fieldwork was made in a fragment of Cerrado (Estação Ecológica de Itirapina), Municipalities of Itirapina and Brotas, State of São Paulo, southeastern Brazil. At this ecological station, S. fuscomarginatus exhibits a complex acoustic repertoire, social interactions and a prolonged reproductive pattern similar to observations of congeneric species at other localities.

Interaction between breeding habitat and elevation affects prevalence but not infection intensity of Batrachochytrium dendrobatidis in Brazilian anuran assemblages.

Chytridiomycosis, an infectious disease of amphibians, is caused by the fungus Batrachochytrium dendrobatidis (Bd) and has been linked to declining amphibian populations worldwide. The susceptibility of amphibians to chytridiomycosis-induced population declines is potentially influenced by many factors, including environmental characteristics, differences among host species and the growth of the pathogen itself. We investigated the effects of elevation and breeding habitat on Bd prevalence and individual infection intensity (zoospore loads) in 3 anuran assemblages of the Atlantic Coastal Forest of Brazil. Bd infection intensity was strongly influenced by elevation and breeding habitat, but we found no evidence of an interaction between those 2 variables in explaining the number of zoospores sampled from individual frogs. In contrast, Bd infection odds were predicted by elevation and by an interaction between elevation and breeding habitat, such that frogs had a higher probability of Bd infection in lotic habitats at low elevations. Our results indicate that Bd persists across a wide variety of habitats and elevations in the Atlantic Coastal Forest. Prevalence and infection intensity of Bd are highest at high elevations where overall environmental conditions for Bd are most favorable. In addition, at low elevations amphibian host habitat choice is also an important determinant of infection. Our study highlights the need to investigate interacting variables of host ecology and the environment simultaneously.

Defensive Vocalizations of Neotropical Anurans

ABSTRACT. The most common defensive vocalization in anurans is the distress call. However, few descriptions of this type of call are available in the literature, especially for the Neotropics. We therefore described the defensive calls of 31 anuran species and evaluated correlations between anuran size and call physical structure (sound pressure level, dominant frequency, and call duration). Defensive calls are most likely an ancestral character in anurans, as this character is widespread over several genera and families. A positive relationship may exist between the physical characteristics of distress calls and chances of avoiding predation, i.e., only larger (than a certain size) frogs produce defensive vocalizations and the larger the frog, the higher the sound pressure level of its screams. This study strengthens our knowledge about defensive vocalizations in anurans and will hopefully instigate new challenges for future research.

Effects of Season, Temperature, and Body Mass on the Standard Metabolic Rate of Tegu Lizards (Tupinambis merianae)

This study examined how the standard metabolic rate of tegu lizards, a species that undergoes large ontogenetic changes in body weight with associated changes in life‐history traits, is affected by changes in body mass, body temperature, season, and life‐history traits. We measured rates of oxygen consumption (V̇o2) in 90 individuals ranging in body mass from 10.4 g to 3.75 kg at three experimental temperatures (17°, 25°, and 30°C) over the four seasons. We found that standard metabolic rate scaled to the power of 0.84 of body mass at all experimental temperatures in all seasons and that thermal sensitivity of metabolism was relatively low (Q10 ≈ 2.0–2.5) over the range from 17° to 30°C regardless of body size or season. Metabolic rates did vary seasonally, being higher in spring and summer than in autumn and winter at the same temperatures, and this was true regardless of animal size. Finally, in this study, the changes in life‐history traits that occurred ontogenetically were not accompanied by significant changes in metabolic rate.

Seasonal changes in daily metabolic patterns of tegu lizards (Tupinambis merianae) placed in the cold (17 degrees C) and dark.

Oxygen consumption rate was measured continuously in young tegu lizards Tupinambis merianae exposed to 4 d at 25°C followed by 7–10 d at 17°C in constant dark at five different times of the year. Under these conditions, circadian rhythms in the rate of oxygen consumption persisted for anywhere from 1 d to the entire 2 wk in different individuals in all seasons except the winter. We also saw a progressive decline in standard oxygen consumption rate (at highly variable rates in different individuals) to a very low rate that was seasonally independent (ranging from 19.1 ± 6.2 to 27.7 ± 0.2 mL kg−1 h−1 across seasons). Although this degree of reduction appeared to take longer to invoke when starting from higher metabolic rates, tegu lizards reduced their metabolism to the low rates seen in winter dormancy at all times of the year when given sufficient time in the cold and dark. In the spring and summer, tegus reduced their standard metabolic rate (SMR) by 80%–90% over the experimental run, but only roughly 20%–30% of the total fall was due to the reduction in temperature; 70%–80% of the total fall occurred at constant temperature. By autumn, when the starting SMR on the first night at 25°C was already reduced by 59%–81% (early and late autumn, respectively) from peak summer values, virtually all of the fall (63%–83%) in metabolism was due to the reduction in temperature. This suggests that the temperature‐independent reduction of metabolism was already in place by autumn before the tegus had entered winter dormancy.

Seasonal changes in blood oxygen transport and acid–base status in the tegu lizard, Tupinambis merianae

Oxygen-binding properties, blood gases, and acid-base parameters were studied in tegu lizards, Tupinambis merianae, at different seasons and temperatures. Independent of temperature and pH, blood oxygen affinity was higher in dormant lizards than in those active during the summer. Haematocrit (Hct) and hemoglobin content ([Hb]) were greater in active lizards resulting in a higher oxygen-carrying capacity. Nucleoside triphosphate content ([NTP]) was reduced during dormancy, but the ratio between [NTP] and [Hb] remained unchanged. Dormancy was accompanied by an increase in plasma bicarbonate ([HCO-(3)]pl) and an elevation of arterial CO2 partial pressure (PaCO2) and CO2 content in the plasma (CplCO2). These changes in acid-base parameters persist over a broad range of body temperatures. In vivo, arterial O2 partial pressure (PaO2) and O2 content (CaO2) were not affected by season and tended to increase with temperature. Arterial pH (pHa) of dormant animals is reduced compared to active lizards at body temperatures below 15 degrees C, while no significant difference was noticed at higher temperatures.