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It is known that crocodilians are able to locate the source of air-borne sound. However, locating the source of water-borne sound is difficult for physical reasons. I tested the ability of American Alligators (Alligator mississippiensis) to determine the direction toward the source of underwater sound by using their tendency to be attracted to slaps on the water surface. To produce surface slapping sounds with no air-borne component, I slapped the surface of the water inside a submerged diving bell and recorded the direction of alligator movements after the sound. The results show that alligators have a directionally biased response to water-borne sounds, indicating that they are capable of locating the source of a sound signal transmitted through the water. It would be physically difficult for the animal to do so by using the differences in time of sound arrival or in amplitude between left and right sides of the animal's head, so it is likely that alligators use other methods such as a sound pressure gradient system.
In Jamaica, free-living male and female-sized Anolis sagrei are exposed to more natural ultraviolet-B (UVB) from sunlight than male and female-sized Anolis lineatopus. In the laboratory, we tested predictions derived from the hypothesis that Anolis possess a mechanism for behaviorally photo-regulating their exposure to UVB depending on their dietary intake of vitamin D3. Anolis sagrei voluntarily exposed themselves more frequently to visible and UVB light and received higher doses of UVB in an artificial light gradient when fed a low vitamin D3 diet for 6 weeks than when subsequently fed a high dietary vitamin D3 diet for 6 weeks. When we returned the anole's diet to the low vitamin D3 regimen for a third 6-week period, UVB exposure remained lower than in the first 6-week period. This suggests an initial UV photo-regulatory adjustment to high dietary vitamin-D3 but a slow return to greater reliance on UVB-induced endogenous vitamin D3 production. Conversely, while exposing themselves to UVB with similar frequency and doses as A. sagrei over the course of the 18-week experiment, A. lineatopus did not show the same decreased attraction to visible and UVB light in response to increased dietary vitamin D3. The response of A. sagrei in the laboratory to visible light without UVB was similar to their response to visible light with UVB. Therefore, the anoles appeared to be responding primarily to visible light. Anolis lineatopus may be unable to use dietary vitamin D3 to restore low vitamin D status.
Frog calls are often stereotyped and only a few species are known to vary the emission of a single note or call greatly. Calls of Physalaemus spiniger were recorded in the field and analyzed in the laboratory. We recognized and describe five different notes or calls: advertisement, territorial, fighting, release, and amplexus. These notes differ in duration, number of pulses per call, and fundamental frequency (Fh1). There was a great variation in the spectral structure and frequency modulation of the advertisement call, which had up to six harmonic frequencies (H). Of these, one to three were visible and two to three were estimated. The greatest sound intensity was recorded in H3 (1.27 kHz) and H4 (1.68 kHz). The note had an average duration of 237.63 ms and 371.57 pulses/note. The advertisement note (A) may occur in conjunction with the territorial note (T), in this case by changing its physical characteristics. The frequency modulations in the notes were both ascendant and descendant and were located anywhere in the note. We identified at least 22 different ways in which the advertisement call was emitted. The function of this variation and the observed patterns are unclear; however, this species is an excellent model for investigating call parameters as only two other species of frogs are known to possess such extensive vocal repertoires.
The tadpole of Physalaemus evangelistai is described from the highlands of the Serra do Espinhaço Mountain Range, State of Minas Gerais, southeastern Brazil. Additionally, a redescription of the advertisement call and natural history information are provided. We compared the tadpole's morphological features with other species described in the Physalaemus genus, including Physalaemus gracilis group: Physalaemus barrioi, Physalaemus gracilis, Physalaemus jordanensis, and Physalaemus lisei. We found minor differences in oral disc proportions, number of marginal papillae rows, and the orientation of the vent tube opening. Advertisement calls (20 calls from three males) were composed of a single harmonic note. Call mean duration was 0.69 sec; mean duration of interval between calls was 13.94 sec; and mean value of dominant frequency was 3.13 kHz. Physalaemus evangelistai breeds during the first half of the rainy season (October to January), building foam nests in temporary ponds at montane meadows.
O girino de Physalaemus evangelistai é descrito a partir de áreas de altitude na Serra do Espinhaço, estado de Minas Gerais, sudeste do Brasil. Adicionalmente, a redescrição de seu canto de anúncio e dados de história natural são apresentados. Comparamos as características morfológicas dos girinos com os descritos para as espécies do gênero, incluindo aquelas do grupo de Physalaemus gracilis: Physalaemus barrioi, Physalaemus gracilis, Physalaemus jordanensis e Physalaemus lisei. Encontramos pequenas diferenças na proporção do disco oral, número de fileiras de papilas marginais e na abertura e orientação do tubo cloacal. Vocalizações de anúncio (20 vocalizações de três machos) são compostas por uma única nota harmônica. A duração média do canto é de 0.69 segundos, a duração média do intervalo entre cantos é de 13.94 segundos e o valor médio da frequência dominante é de 3.13 kHz. Physalaemus evangelistai reproduz-se durante a primeira metade da estação chuvosa (entre outubro e janeiro), construindo ninhos de espuma em poças temporárias em campos de altitude.
Stable isotopes are commonly used to examine various aspects of animal ecology. The use of stable isotopes generally proceeds under the implicit assumption that resource use is the only factor driving variation in stable isotope levels; however, a wealth of studies demonstrate that a range of common ecological factors can affect the behavior of stable isotopes in animal tissues and potentially confound inferences. For example, studies of some invertebrates and endothermic vertebrates show that animals fasted for ecologically realistic time periods have higher nitrogen (δ15N) or lower carbon (δ13C). We examined whether realistic fasting would influence the stable isotope composition of one of the most metabolically efficient ectothermic vertebrates, the Eastern Red-backed Salamander, Plethodon cinereus. We fasted salamanders for 7, 14, 21, 28, or 35-day intervals and examined whether δ15N or δ13C levels of tissues changed between fasted and fed animals. We investigated whether body condition (body mass to length and C:N [an index of lipid levels]) declined in fasted animals and whether there was a relationship between C:N and δ15N or δ13C. Body mass to length index and C:N, δ13C, and δ15N of tail and liver tissues did not differ between fasted and fed animals between 7 and 35 days. Because of their extreme metabolic efficiency, vertebrate ectotherms such as lungless salamanders (Plethodontidae) may not show the effects of fasting on stable isotopes observed in endothermic vertebrates and some invertebrates. This difference should lead to simpler interpretation of stable isotope results from field studies of these animals.
Acoustic signals are the main communication vehicle for most anuran species, and males typically use advertisement calls to attract females and to interact with other males in a chorus. The role of the environment in the evolution of the advertisement call is still largely unknown, and the recognition of different selective pressures may improve our understanding of anuran communication system. The aim of this study was to investigate the effect of micro-habitat at calling sites on advertisement call structure and propagation in a population of the treefrog Hypsiboas crepitans. Males of this species typically call from elevated sites in vegetation or from sites where their body is partially submerged in water. Our analysis of call parameters of males calling from these sites showed that both dominant frequency and pulse rate were significantly lower when males called partially submerged in water compared to males calling from elevated sites in vegetation. Both pulse rate and dominant frequency have been shown to be important in species recognition among anurans, and they play a role in sexual selection and sound propagation. Our analysis of the effect of calling site (elevated or partially submerged) on signal propagation showed that the efficiency of transmission did not differ between sites.
The Yosemite Toad (Anaxyrus (formerly Bufo) canorus) is a high-elevation species endemic to the central Sierra Nevada mountain range in California whose populations are in decline. There is limited information on their terrestrial movement and habitat use, which impairs our understanding of the ecology and habitat needs of this sensitive species. I present radio-tracking data collected from 35 adult toads in the Sierra National Forest during daylight hours in the late spring and summer of 2007–2009. Movements, microsite cover type, and terrestrial habitat are analyzed and interpreted with regard to life-history characteristics of A. canorus. Adult toads moved a mean distance of 270 m from aquatic breeding sites, and the maximum distance recorded was 1.26 km. Females moved significantly longer distances than did males and had a larger home range. Distance traveled was related to ordinal day as well as the interaction between day and sex. Adult A. canorus used terrestrial environments extensively and were found in the mixed-conifer forest in dry habitat. Burrows were the most commonly used cover type, but other protective cover such as logs, rocks, and tree stumps were also used. The locations occupied by adult toads in the terrestrial environment were structurally different than other surrounding areas; occupied sites had less canopy cover and fewer woody species than did unoccupied sites. The results of this study have implications for identifying population processes such as metapopulation dynamics, as well as for management purposes such as identifying sensitive habitat and establishing protective areas for A. canorus in the terrestrial environment.
The defensive secretions of anurans contain a large array of chemical compounds that are synthesized in the granular glands and released onto the skin. We used histological and peptidomic analyses to investigate the skin glands and their products in Litoria aurea, Litoria ewingii, and Litoria raniformis, which were introduced to New Zealand from Australia approximately 150 yr ago. The skin glands were induced to release their product by either norepinephrine or electric stimulation. Granular glands in all three species are distributed evenly in both dorsal and ventral skin and share morphological features common in other anurans, such as a contractile myoepithelium that surrounds the syncytial secretory unit. However, differences are observed in the granular ultrastructure between L. ewingii and the more closely related L. aurea and L. raniformis. The latter have larger glands with granules that are opaque and contain homogeneously spaced, diaphanous vesicles, whereas the substructure of the granules in L. ewingii is homogeneous and consists of miniscule vesicles that are either electron opaque or diaphanous. Comparatively large mucous glands in the small-bodied L. ewingii may be attributed to increased mucous requirements due to differences in microhabitat use. Nanospray mass spectrometric analyses confirmed the presence of several unidentified peptides, as well as 11 peptides described previously. Both exposure to norepinephrine and mild electric stimulation of the skin triggered the bulk discharge of gland contents. We discuss potential functional specializations of gland structure and peptide content as mechanisms for predator or pathogen defense.
The genus Aparasphenodon is poorly known. Of the four species, the larvae of only one have been described, and the advertisement calls of all taxa remain unknown. Here, we describe the tadpole, adult coloration, and advertisement calls of Aparasphenodon arapapa. We also provide data that extend its known distribution 170 km to the south, from the type locality in Ituberá to Una, Bahia, Brazil. In addition, we report larval morphology related to bromeligenous habitat specialization of tadpole and metamorph oophagy for the first time in the genus. The advertisement call is composed of one multipulsed note with mean duration of 150 ms. Whether the observed oophagy is obligatory or opportunistic remains unclear, suggesting that further studies are warranted. Our observations provide insight into the behavioral and morphological diversity in the genus Aparasphenodon, and may guide future studies of this unique group of anurans.
The importance of plethodontid salamanders in forested ecosystems has been recognized for decades, and studies aimed at quantifying salamander biomass and determining habitat requirements have become more common. However, there is a lack of knowledge on the use and contribution of vertical structures (e.g., wet rock faces) to total salamander biomass within a forested ecosystem. The purpose of our study was to characterize the population density, biomass, and habitat use of a wet rock face by a stream-salamander assemblage. We estimated the population density to be 14.69 salamanders m−2 and the total biomass estimate to be 27.16 g m−2, which is more than two times greater than any salamander biomass reported previously in the eastern United States. We also found significant habitat partitioning of the vertical gradient by the three species of salamanders in the assemblage. The stable microclimate and increased protection from other predators (e.g., mammals, snakes, and ground-foraging birds) provided by wet rock faces likely leads to the increased amount of biomass we found in this study. Although the salamanders are likely protected from most noncaudate predators, the spatial structuring in the assemblage still follows an intraguild predation gradient found in horizontal habitats.
Some prey species vary the intensity of antipredator responses according to the perceived level of threat associated with different concentrations of chemical cues related to predation. Here, we examine whether Red-Backed Salamanders (Plethodon cinereus) respond to different concentrations of damage-released cues from the tails of conspecifics in a threat-sensitive manner. We exposed salamanders either to a control or to damage-released cues from conspecifics at one of three different concentrations. We found that salamanders exposed to damage-released cues significantly decreased their activity compared to salamanders exposed to a control. However, the intensity of the responses was not related to the concentration of the cue, suggesting that individuals of P. cinereus do not respond in a threat-sensitive fashion at the concentrations tested.
The Cerro Azul Formation of Argentina has yielded one of the highest diversities of squamate reptiles for the upper Miocene of South America including tupinambine teiids (Tupinambis sp.), “colubrids,” and viperids. Here, we describe new remains of Tupinambis sp. and “Colubridae” from this Formation as well as the first records of teiine teiids and boid snakes. The teiine represents the oldest record of this subfamily in South America. The squamate assemblage of the Cerro Azul Formation is consistent with the mammalian fauna in supporting the interpretation of a Chacoan-type palaeoenvironment for the upper Miocene of Central Argentina.
We describe the external morphology, buccal cavity, chondrocranium, hyobranchial skeleton, and musculature of the tadpole of Rhinella achavali (Achaval's Toad), along with its karyotype. Tadpoles were found in a small, permanent stream and were showing schooling behavior. The characterization of the proposed species groups within Rhinella cannot be currently improved using external larval morphology, as it seems to be much conserved within this genus. Buccal cavity morphology confirms the distinctiveness of the Rhinella veraguensis (Veragua Toad) group with respect to other known Rhinella. Musculoskeletal character states are similar among bufonids, although within this family the basal genus Melanophryniscus shows some distinctive states. The karyotype is composed of 22 bi-armed chromosomes, with secondary constrictions in pair 7, as found in the other species in the Rhinella marina (Marine Toad) group.
We report on the reproductive biology of Rhacophorus vampyrus (Rhacophoridae, Anura) from the Lang Bian Plateau in southern Vietnam. Unlike most other members of the genus Rhacophorus, R. vampyrus is a phytotelm breeder and reproduces in water-filled tree hollows. The species shows a unique tadpole mouthpart morphology not reported for any other anurans: presence of a specific serrated horny arch on the upper jaw and two large, fang-like horny teeth on the lower jaw. This, together with the presence of a large extensible stomach and relatively short digestive tract length, indicates an adaptation toward macrophagous feeding. We observed two clutch types in R. vampyrus: fertilized eggs included in a typical foam nest and unfertilized eggs, apparently having a trophic function, enveloped by dense mucous. The digestive tracts of all tadpoles examined contained up to 40 trophic eggs and showed no remains of any other food. Keratinous mouthparts undergo considerable remodeling during tadpole development presuming the change of feeding mode in ontogeny. We speculate that these findings indicate that the tadpole of R. vampyrus is an obligatorily and highly specialized oophagous type with unique mouthpart structures. The advanced form of parental care, including the maternal provisioning of unfertilized eggs, is reported for the first time for the genus Rhacophorus and is the second documented record for the Rhacophoridae.
Careful examination of morphological characters, color patterns, and advertisement calls strongly supports the placement of Dendropsophus allenorum (Duellman and Trueb, 1989) (Cuzco Reserve Frog) into the synonymy of Dendropsophus timbeba (Martins and Cardoso, 1987) (Cardoso's Treefrog).
Um exame cuidadoso dos caracteres morfológicos, dos padrões de coloração e dos cantos de anúncio suportam fortemente que Dendropsophus allenorum (Duellman e Trueb, 1989) deva ser considerado um sinônimo júnior de Dendropsophus timbeba (Martins e Cardoso, 1987).