The present investigation examined the extracutaneous pigmentation pattern of three species of anuran amphibians, Dendropsophus nanus, Physalaemus cuvieri, and Rhinella schneideri, during the course of their breeding seasons. Pigmentation intensity in the different organs was graded on a 4-category scale, in which category 0 refers to organs without pigment and category 3 refers to intensely pigmented organs, with 2 intermediate stages of progressively stronger pigmentation. Rhinella schneideri showed testicular pigmentation, with intra-specific variation (categories 0 and 1). In P. cuvieri the pigmentation in the lungs varied in time: all the animals showed pigmentation (category 1) at the beginning of the breeding season, and as the season progressed the absence of pigments became the most common pattern. In the liver of the first animals collected, the pigment intensity was high (category 2) with many iridophores present, but in the last specimens collected no iridophores were found. The variation in D. nanus occurred in the kidneys, where animals collected at the beginning of the season did not show pigmentation. Renal veins displayed few melanocytes (category 1); animals collected at the end of the season showed more pigmentation in the kidneys (category 2), whereas in the renal veins the intensity remained the same. The changes observed in the extracutaneous pigment system in some organs, during the reproductive period, may be due to physiological alterations or may represent a species-specific characteristic.

We describe a new species of the hylid frog genus Scinax from the Peruvian Upper Amazonian Lowlands (area of Iquitos, Region Loreto, Peru). The new species belongs to the Scinax ruber clade and differs from all its members by having the dorsal skin slightly to coarsely shagreen, by lacking conspicuous ulnar and tarsal tubercles, and in life by having a distinct light olive-green coloration on dorsum, bright yellow flanks with distinct black spots, black posterior surfaces of thighs, and gold to bronze iris.

A new, miniaturized species of Phyllodactylus Gray from Guerrero, Mexico is described. The species appears to be the smallest American species of leaf-toed gecko. The diploid karyotype consists of a graded series of 36 acrocentric and 2 subtelocentric chromosomes; the telocentric pair is the second largest. The new form is morphologically very similar to P. duellmani, but is electrophoretically quite distinctive having a genetic distance of 0.839. The new population is also meristically quite similar to allopatric P. bordai, but can be distinguished by its small size at which reproductive maturity is attained and by the number of transverse ventrals.

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.

Breeding aggregations are common in anurans during reproduction. In these aggregations, males can space themselves or randomly distribute themselves in the available space, and they can occupy the same position for long periods of time or shift from one position to another frequently. I investigated male spacing patterns and individual site fidelity of Physalaemus fischeri at a moderately flooded shrub plot during 21 consecutive nights at a locality in the central llanos of Venezuela. Male positions and nearest neighbor distances were determined nightly. I found 35 different males at 53 calling positions. Not all males were active simultaneously. Nineteen males occupied the same calling position for more than one night, either consecutively or not. The number of nights of consecutive occupation of a position by the same male was 2.59 ± 1.12 (mean ± sd; max = 5 nights, N = 17 males) and the total number of nights (consecutive and non-consecutive) was 3.00 ± 1.41 (mean plusmn;sd; max = 6 nights, N = 15 males). The modal nearest neighbor distance was 2.5 m and about 58% of the inter-male distances were below 6 m. The Clark and Evans index (R) and the Thompson's test, performed for each observation night, indicated that males distributed themselves regularly in most nights. There was a positive association between R and nearest neighbor distances (Spearman r_s = 0.72, p = 0.04), thus, regular spacing was associated with spatial segregation among males. The results indicate that breeding aggregations of P. fischeri males are structured but dynamic, because males space themselves within the aggregation and show site fidelity, but only during a few nights. Male segregation is suggestive of acoustically mediated spacing, because male-male combat was rare. In addition, spacing and occupation of a stable position over short periods may entail breeding advantages that still remain to be investigated.

In the present study we investigate the changes in the level of serum magnesium and calcium ions, and their possible mode of regulation during progression of hibernation of the anuran, Duttaphrynus melanostictus, the Indian Common toad. Though these ions have a profound effect on the thermoregulatory center in the brain of even poikilothermic vertebrates like the Indian Common toad, not much information is available about the system. We attempt to expose the role of these ions in this system. In this animal, serum magnesium and calcium levels are known to be significantly low during the entry phase as well as during the awakening phase from the hibernation period as compared to the deepest phase. We tried to correlate the role of serum magnesium and calcium ions during different phases of this poikilothermic animal.

Two dipsadid snakes occur on the island of Dominica, Lesser Antilles. In June 2008, we conducted visual encounter surveys to document activity periods of Alsophis sibonius and Liophis juliae at Cabrits National Park. Based on 165 observations of A. sibonius over the course of 71.25 search hours, we determined that daytime activity is bimodal and inversely correlated with temperature. Most snakes were found in moderately disturbed habitats, near trails, and on leaf litter. All nine L. juliae were observed during the morning. More individuals of both species were observed at a greater range of times on rainy days. Our data supported predictions that A. sibonius would exhibit a bimodal activity period and would extend activity when cool/rainy weather moderated periods of midday heat. Neither species appeared to be deterred by human-mediated habitat alterations, effectively exploiting stone ruins and areas near trails.

The tadpole and vocalizations of Phyllomedusa centralis are described based on individuals from the type locality, Chapada dos Guimarães, State of Mato Grosso, Brazil. An opaque abdomen, upper jaw sheath medially higher, and an abundance of oral disc papillae characterize the tadpole of P. centralis. Phyllomedusa centralis, P. ayeaye, P. oreades, and P. megacephala are similar in inhabiting small streams, larvae with medially high upper jaws sheaths, spiracle opening free from body, and a ventral fin about three times deeper than the dorsal fin. The vocal repertoire of P. centralis consists of three different calls (“single call”, “compound call”, and ”response call”). These calls differ from those of other species of the hypochondrialis group by their low dominant frequency, short note duration, and broad frequency range with minimum (fundamental) and maximum frequencies coincident with the dominant frequency.

Several previous studies have established that the introduction of the American bullfrog, Lithobates catesbeianus, produces negative effects on native communities. Herein, the American bullfrog is reported for the first time in the province of Buenos Aires, Argentina in the locality of 9 de Julio. The stomach contents of the collected specimens were examined and the reproduction of the species was also confirmed at the study area. A total of 85.7% (n = 30) of the analyzed stomachs contained prey items, and eleven of these were identified. The prey items belonged mostly to coleopterans (50%) and vertebrates (11%). The pathogen Batrachochytrium dendrobatidis was not found on skin samples examined. The installation of Lithobates catesbeianus breeding facilities contributes to the incidental release of this species. A tightening of rules in the regulation of aquaculture activities and the use of control programs for naturalized populations are necessary to address the increasing dispersion of the species in Argentina and potential ecological problems.

Chironius bicarinatus is a common colubrid snake, widely distributed throughout the Atlantic Forest. Field observations of copulation and combat, combined with data on preserved and captive snakes, as well as on specimens brought to Institute Butantan provided a better characterization of the reproductive cycle of this species. Chironius bicarinatus has a seasonal reproductive cycle with extended vitellogenesis and ovulation, and oviposition occurring at the onset of the rainy season (austral spring). Recruitment of newborns occurred mainly at the end of the rainy season. Clutch size ranged from five to 14 and relative clutch size ranged from 0.55 to 0.62. Copulation was observed four times, always in April (austral autumn) at the onset of vitellogenesis. These records correspond to the activity peak of males in the field. Thus, mating may occur prior to ovulation (in austral spring) indicating a dissociated reproductive pattern. We suggest that combat in November (in austral spring), recorded in a previous study, may be related to the presence of androgens in snakes during the non-mating season.

Aspects of natural history of the vine snake Oxybelis fulgidus from the northern region of Brazil were inferred based on the analysis of 106 preserved specimens (55 males and 51 females), and from a review of records in the published literature. Males mature at smaller size than females. Differences in body length and shape were also found among adult females and males: adult females are larger in mean snout-vent length and have relatively larger heads and shorter tails. Females have an extended seasonal vitellogenic cycle from April to December (mainly throughout the dry season). Oviductal eggs and egg-laying were recorded from September to December, while births occurred from January to April. Fecundity varied from four to twelve eggs or vitellogenic follicles (n = 13), and was positively correlated with female body length. Testicle volume is significantly larger from February to July (mainly in April and May; end of the rainy season), however the deferent ducts diameter do not differ significantly throughout the year. We hypothesized that both males and females may have an associated reproductive pattern, both synchronized in the end of the rainy season. Oxybelis fulgidus feeds on lizards (mainly iguanian) and passerine birds. Apparently, females feed more frequently on birds than males.