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Anuran larvae (tadpoles) can alter their behavior and morphology in response to predators with which they have coevolved. Furthermore, tadpoles of a few species are capable of learning, which can elicit or reinforce predator-avoidance behaviors. However, it remains unclear how widespread this capacity for learning is among anurans and whether it is biased in favor of evolutionarily familiar predators. Here, we test whether prior experiences will modify the behavioral response of Lowland Leopard Frog Lithobates (Rana) yavapaiensis tadpoles to Green Sunfish Lepomis cyanellus, a recently introduced predator. We exposed focal tadpoles for 10 days to the chemical and visual cues of one of three conditioning treatments: a cricket-fed Green Sunfish, a tadpole-fed Green Sunfish, or a control tank without predator. Subsequently, we measured the swimming activity of focal tadpoles in response to a neutral cue (water) and the chemical cues of Green Sunfish. No difference between conditioning treatments was observed in response to the water cue. In contrast, tadpoles that had previously experienced either of the sunfish conditioning treatments displayed significantly higher swimming activity than control tadpoles for 2–4 min after exposure to the sunfish chemical cues. Our results indicate that the behavior of tadpoles can be altered by prior experiences, even in the absence of alarm cues. In addition to providing another example of learning in tadpoles, our results suggest that tadpoles may have a broad learning template that can be applied to organisms with which they have recently come into contact.
We describe a new species of Pristimantis in the subgenus Hypodictyon ridens Species Series from the type locality in Parque Nacional General de División Omar Torrijos Herrera on the Cordillera Central in central Panama. This species is similar to Pristimantis caryophyllaceus but can be differentiated from that form by snout–vent length (female Pristimantis educatoris ∼ 27% larger than P. caryophyllaceus), round, globular, and projecting subarticular tubercles on all digits (not projecting in P. caryophyllaceus); finger disk covers even, round, disk pads ovoid, toe disk covers expanded and palmate, and toe pads even and broadened (finger and toe disk covers and pads rounded in P. caryophyllaceus); outer metatarsal tubercle large, elongate, and projecting (obscure and small in P. caryophyllaceus). We also report and describe female parental care of eggs.
Phosphate pollution is a widespread problem resulting from agricultural runoff and urban wastewater. Phosphates are known to cause eutrophication and algal blooms, but little is known about phosphate toxicity, particularly among amphibians. To investigate possible phosphate toxicity, Hyla chrysoscelis tadpoles were exposed to concentrations ranging from 0–200 mg/L PO4-P for 15 days. Phosphate was found to have no effect on the survival, growth, or developmental stability of the tadpoles, indicating that phosphate may not be toxic to this species at levels associated with anthropogenic inputs. Phosphate was found to increase the pH of the test water, which, in conjunction with other stressors, may have negative effects within aquatic communities. However, phosphate could also affect anuran tadpoles positively by increasing algal food resources. Because phosphate is a ubiquitous pollutant, further testing using more complex experimental designs is warranted.
Reproductive biology of males in the Guam population of the Brown Treesnake, Boiga irregularis, was investigated through monthly examinations of the urogenital system organs and plasma testosterone levels. All males examined during the 12 consecutive months of the study were spermatogenic and had sperm in the ductus epididymis and ductus deferens. No evidence of testicular recrudescence or regression was observed. Testis mass did not vary among months. Epithelial height of the kidney sexual segment was the only feature examined that varied significantly among months, with lowest heights observed in May through July. Despite this variation, the sexual segment in all males was hypertrophied and contained secretory granules. Plasma testosterone levels did not vary significantly among months, were relatively low compared to those of most other snake species, and were extremely variable among individuals. There were individuals with near-zero levels in most months. Overall, the reproductive biology of males on Guam is aseasonal. In light of this finding, the claim of seasonality in the putative source population is reassessed. Testosterone levels were independent of coelomic fat body mass, which was extremely variable among males and, in many cases, quite low. Observations on morphological features suggest that individual reproductive capacity increases disproportionately with increasing body size. The possibility of facultative aseasonal/seasonal reproduction in the species is discussed. The observed capacity for continuous spermatogenesis and its relative independence from body condition may facilitate the invasive capabilities of this ecologically damaging species.
There is a great need for proactive approaches to avoid amphibian declines. We investigated the possibility that antioxidant stress markers might serve as a proactive measure of physiological stress in anuran tadpoles. Commercially purchased American Bullfrog tadpoles (Lithobates catesbeianus, Gosner stage 36–37) were subjected to 0- (control), 0.1-, 0.5-, 1.0-, and 2.0-mg/L paraquat for 24 h. Liver and muscle (tail clip) tissues were removed and analyzed for catalase, superoxide dismutase (SOD), general peroxidase, and glutathione reductase (GR) activities. In the controls, there was no significant difference in GR activity in tissues collected from the liver and the tail; however, peroxidase, SOD, and catalase activities ranged from two- to 20-fold higher in the liver than in the muscle tissue. Treatment with paraquat resulted in significant increases in SOD, general peroxidase, and GR activities in the liver tissue, whereas the high constitutively expressed catalase activity remained unchanged. GR activity also increased significantly in the muscle tissue when the tadpoles were treated with 2-mg/L paraquat, but the activities of the other three antioxidant enzymes did not vary significantly from the control values in this tissue regardless of the paraquat treatment. After 24 h of paraquat treatment, all tadpoles at all treatment levels were alive and appeared to be vigorous, suggesting that the bullfrog is very tolerant to paraquat toxicity. It is proposed that this tolerance is caused by the stress-induced increases of antioxidant enzyme activity such as SOD, general peroxidases, and GR, as well as, the high constitutive activity of catalase. These findings suggest that, with refinement and further studies, antioxidant markers may be important indicators of sublethal environmental stress in amphibians.
A new species of Stefania (Anura: Cryptobatrachidae) from northern Amazonas, Brazil, is described. Three specimens were collected in the Parque Nacional do Pico da Neblina, municipality of São Gabriel da Cachoeira, Amazonas State, northern Brazil, at 110–850 m elevation in dense closed canopy forest and in dense closed canopy montane forest. The new species is characterized by head length slightly greater than width, canthus rostralis concave, toes more than 50% webbed, dorsal skin smooth or shagreened. This is the first record of a species of Stefania endemic to Brazil.
The thermal quality of diurnal refuges is important to the performance and survival of nocturnal reptiles. We studied refuge use on both slopes of an east–west-oriented hill by the thigmothermic gecko Homonota darwini, the southernmost-distributed nocturnal lizard in the world, in the vicinity of Bariloche, Rio Negro, in the Patagonia of Argentina. Because of the harsh climatic conditions in Patagonia, suitable refuges are limited, and retreat-site use is important for these geckos. Homonota darwini used refuges significantly more frequently on the warmer western slope in our study site. Geckos on the western slope used those refuges with higher temperatures regardless of size and thickness of rocks that acted as retreats. We tested whether refuge temperature affected locomotor performance of these lizards. Performance experiments showed that maximum sprint speed was affected by the temperature of the refuges. Refuges at 22.5°C allowed lizards to achieve their fastest sprint performance. Unexpectedly, sprint performance of lizards that used refuges with temperatures >32°C was the lowest among all tested refuge temperatures (18°, 22.5°, 27.5°, and 33°C). Our data illustrate the importance of the thermal quality of refuges for reptiles living in extreme environments.
The herpetofauna of the Tuscan Islands (Central Italy) is well known and represents an ideal subject to understand the role of current and historical factors responsible for biogeographical patterns in a complex archipelago. Multidimensional Scaling, cluster analyses, species-area relationships, Mantel tests and co-occurrence statistics were used to investigate the influence of current geography and Pleistocene connections with the mainland on the structure of insular communities. Although reptile colonization likely occurred via land bridges for islands that were connected to the mainland in the Pleistocene, a long time relaxation (species extinction by island habitat loss after disconnection and new colonization by over sea dispersal or human-assisted introductions) equilibrated the faunas according to island area. Biogeographical similarities among islands increased for islands located farther from Corsica and Tuscany, thus suggesting that, for remote islands, interisland faunal exchanges occurred more frequently than mainland-island colonization. Also, a possible influence of Pleistocene geography emerged more clearly when populations suspected to be introduced by man were removed. Co-occurrence analyses indicated a nonrandom distribution influenced by island area and distance, suggesting that the time elapsed since post-Pleistocene disconnection may have reshaped biogeographical similarities by an increase in competition resulting from reduction in island areas and introduction of certain species. From a conservation viewpoint, the land-bridge distribution of organisms with poor mobility should be carefully considered in conservation biogeography, because depletion of island populations cannot be balanced by new immigrations from the mainland, whereas introduction of nonnative species may have a negative impact on the original fauna.
Many declines of amphibian populations have been associated with chytridiomycosis, a disease caused by the aquatic fungus Batrachochytrium dendrobatidis (Bd). Despite the relatively high prevalence of chytridiomycosis in stream amphibians globally, most surveys in North America have focused primarily on wetland-associated species, which are frequently infected. To better understand the distribution and prevalence of Bd in headwater amphibian communities, we sampled 452 tailed frogs (Ascaphus truei and Ascaphus montanus) and 304 stream salamanders (seven species in the Dicamptodontidae and Plethodontidae) for Bd in 38, first- to third-order streams in five montane areas across the United States. We tested for presence of Bd by using PCR on skin swabs from salamanders and metamorphosed tailed frogs or the oral disc of frog larvae. We detected Bd on only seven individuals (0.93%) in four streams. Based on our study and results from five other studies that have sampled headwater- or seep-associated amphibians in the United States, Bd has been detected on only 3% of 1,322 individuals from 21 species. These results differ strongly from surveys in Central America and Australia, where Bd is more prevalent on stream-breeding species, as well as results from wetland-associated anurans in the same regions of the United States that we sampled. Differences in the prevalence of Bd between stream- and wetland-associated amphibians in the United States may be related to species-specific variation in susceptibility to chytridiomycosis or habitat differences.
Color is used in social signaling by many species. Male Eastern Fence Lizards, Sceloporus undulatus, possess sex-specific dorsal and ventral coloration, including vivid blue badges on their throat and abdomen, which they behaviorally display to conspecifics. The presence of abdominal badges serves as a signal of an individual's sex, but the significance of badge and integument coloration for signaling fitness traits is unknown. We tested for associations between coloration (color of the dorsal surface, chest, and abdominal and throat badges, as well as relative badge size) and a range of fitness-relevant morphological traits (body size and condition, tail and hind-limb length, and head size) in male Eastern Fence Lizards from two sites. Larger males have darker colored abdominal badges and relatively larger abdominal and throat badges. Males with longer tails and wider heads have darker dorsal coloration, and there is a correlation between head length and the color of the black abdominal badges, but this is not consistent between sites. Adults also have darker chest and dorsal coloration than do juveniles. These relationships suggest that S. undulatus color may signal competitive ability to male opponents. However, if this were the case, we would expect body condition and limb length, morphological measures that are tightly correlated with these fitness traits, to also correlate with coloration. This was not evident from our data. Therefore, despite significant variation in coloration of male S. undulatus, it is unlikely to reflect fitness associated with the traits measured in this study.
The Green Anole, Anolis carolinensis, has been widely studied in terms of its behavioral ecology. However, few studies have simultaneously compared the relative strengths of predation and male competition across temporal and spatial scales in Green Anoles, or other reptile species. We took an indirect experimental approach to compare these forces in Green Anoles by using attacks on clay models as a proxy for the relative intensity of predation and male competition. We measured the proportion of attacks on clay models in two divergent Green Anole populations with distinct habitats (discrete and continuous vegetation) across three seasons (fall, winter, and spring) and found strong evidence for spatial and temporal variation in the relative intensity of each component of selection. The frequency of bites from male Green Anoles was generally higher at an urban locality, whereas the frequency of bites from nonlizards was higher at a natural swamp locality. We also detected temporal variation in the intensity of these processes at both locations, with the intensity of male competition and predation changing in a concomitant fashion, the most intense periods occurring during the fall and spring months and the least intense during the winter months. Our results imply that mortality within some seasonal reptile species is composed of periods of relative calm punctuated by brief but intense “one-two punch” periods of selection.
We provide descriptions for two new species belonging to the Liolaemus montanus group from northern Argentina. The new species are similar to Liolaemus nigriceps and Liolaemus multicolor. However, the new species differ from these taxa, and all other members of the montanus group, in a number of characteristics. The first new species differs from L. nigriceps in the following ways: smaller body size, dorsum of head grey, and variegated throat, and most males exhibit supernumerary precloacal pores. The second new species differs from all other members of the montanus series in having frontonasal scales forming a convex protruding area. It differs from L. multicolor in that males never show blue scales, in the lack of projecting scales on the anterior margin of the auditory meatus, in having an immaculate throat, and in the lack of supernumerary precloacal pores. The first new species occurs throughout the high elevation (3,500–4,300 m) of the puna region situated at the western edge of the southwest Salar de Arizaro (Salta Province, Argentina), an ancient hypersaline dehydrated lake. The second new species is known only from a restricted area on the hypersaline margins of the same ancient lakebed, where plant cover is quite scarce with small grassy plants, and the ground surface is salty. The discovery of these new taxa supports the hypothesis that large saline depressions, such as Salar de Arizaro, are natural vicariant barriers that favored speciation in this genus.
Proveemos de la descripción de dos nuevas especies pertenecientes al grupo de Liolaemus montanus del norte de Argentina. Las nuevas especies son similares a Liolaemus nigriceps y Liolaemus multicolor, las cuales también viven en la región de la puna. De todos modos, las nuevas especies difieren de aquellos taxa, y de otros miembros del grupo montanus en varios caracteres. La primera nueva especie difiere de L. nigriceps de la siguiente forma: tamaño más pequeño, menor número de escamas alrededor del cuerpo, dorso de la cabeza gris, garganta variegada, y la mayoría de los machos exhiben poros precloacales supernumerarios. La segunda nueva especie difiere de todos los miembros de la serie montanus por contar con las escamas frotonasales formando un área convexa prominente. Difiere de L. multicolor en que los machos nunca presentan escamas azules, la ausencia de escamas proyectadas sobre el margen del meato auditivo, en contar una garganta inmaculada, y por carecer de poros precloacales supernumerarios. La primera nueva especie se encuentra en grandes elevaciones (3,500–4,300 m) de la región de la puna al oeste del Salar de Arizaro (provincia de Salta, Argentina), un antiguo lago hipersalino desecado. La segunda nueva especie es conocida solamente para un área restringida en los márgenes hipersalinos de ese mismo salar, donde la cobertura de las plantas es muy escasa con pequeñas plantas y donde el suelo es salino. El descubrimiento de estas nuevas especies soporta la hipótesis de que las grandes depresiones salinas, tal como el Salar de Arizaro, son barreras vicariantes naturales que habrían favorecido la especiación en este género.
Red Imported Fire Ant colonies were allowed access in the laboratory to eggs of eight reptilian and one avian species. The ants were allowed to forage on the eggs for approximately one week each after which the eggs were removed from the foraging arenas. Evaluations of the impact of fire ant foraging on the eggs were made daily, and final evaluations were made upon removal from the arenas. Red Imported Fire Ants were not able to penetrate healthy Bobwhite Quail eggs, the only avian species used in this trial. The foraging ants were able to penetrate the eggs of Diamondback Terrapins, Yellowbelly Sliders, Eastern Painted Turtles, and Loggerhead Sea Turtles but were not able to penetrate the eggs of Florida Softshell Turtles or Musk Turtles. The ants were able to enter the eggs of Burmese Pythons and Yellow Rat Snakes. Results from this study suggest Red Imported Fire Ants may have a more prominent role in the decline of native reptilian species than was previously thought. Further studies, especially in the field, are necessary to determine the true impact.
We evaluated the effect of a potentially stressful urban aquatic environment on growth and development of Fowler's Toad (Bufo fowleri) larvae. We reared larvae to metamorphosis in water from urban and forested streams in a laboratory setting. We found no evidence of oral disc anomalies associated with urban environments, but we did find that tadpoles in these environments were smaller at 26 days of age (but not at metamorphosis) and metamorphosed faster than tadpoles reared in water from forested streams. The observed results were partially consistent with the predictions of H. M. Wilbur and J. P. Collins, who suggested in 1973 that stressful aquatic environments should result in an earlier date of metamorphosis for larvae attempting to escape that environment. We suggest further work to pinpoint factor(s) responsible for the results we observed, and we relate our findings to previous findings of declines in amphibian species richness in the study area.
We surveyed whiptail lizard populations for seven summers (2000–2006) in riparian forests along the Rio Grande in central New Mexico. We captured 5,382 individuals from three parthenogenic species (Aspidoscelis exsanguis, Aspidoscelis neomexicana, and Aspidoscelis uniparens) including 129 hatchlings (young-of-the-year) that were later recaptured as adults. Growth data were fit to a logistic growth model and compared using a likelihood ratio test. Comparisons of growth rates showed that A. exsanguis grew faster than both A. neomexicana and A. uniparens and attained a larger snout–vent length (SVL). Comparisons of capture rates showed that species had similar activity patterns during the summer. Captures of adults peaked in mid-June and decreased in August. Hatchlings became active at the end of July and captures peaked in September. Some individuals were captured several seasons indicating that lizards lived for at least 3–4 yr. Our study shows both similarities and differences in life-history characteristics for three closely related and coexisting whiptail species.
Iguana is a large-bodied clade of extant iguanid including the species Iguana delicatissima and Iguana iguana. Historically, these two species have been diagnosed based primarily on a single external morphological character: presence or absence of the subtympanic plate. We further diagnose both species based on the shapes of skull bones and provide illustrations of the Iguana delicatissima skull.
We used capture-recapture techniques and skeletochronological analysis to investigate body size, population size, and age structure of a population of Palmate Newts (Lissotriton helveticus) living in two adjacent lakes at 2,300 m in Andorra (Eastern Pyrenees). Females were larger (minimum–maximum, 31.0–47.0 mm vs. 32.0–42.0 mm) and heavier (0.8–2.1 g vs. 0.5–1.8 g) than males. The total adult population of the two lakes is estimated at 338–245 individuals. Both sexes mature in three years; males live for nine years and females up to eight years. Interpopulational differences in demographic traits between this population and low-altitude populations of L. helveticus do not include the predicted pattern of delayed sexual maturity and larger longevity that would be expected to exist in higher altitude populations.
Geographic variation in body size may reflect adaptations to local environments, and sexual size dimorphism (SSD) arises from ultimate and proximate factors acting differently on males and females in those environments. The Painted Turtle (Chrysemys picta) is a wide-ranging North American freshwater turtle species with known female-biased SSD. We hypothesized that, in more seasonal environments, the disparity between adult female and male body size would be more pronounced (i.e., the sexual dimorphism index [SDI, female body size/male body size] would be higher) than in more moderate environments because selective pressures on females to maximize reproductive output would result in relatively larger body sizes (fecundity advantage hypothesis) in extreme environments. We predicted that the SDI would be higher in populations at northern latitudes and middle longitudes than in southern and coastal populations. We conducted linear and nonlinear regression analyses using data from the literature and museum records, extrapolated data, and unpublished data on adult male and female carapace and plastron lengths from 65 locations. In contrast to our prediction, SDI decreased with increasing latitude. With respect to longitude, the trend supported our prediction in that the SDI was slightly higher for interior populations and lower for coastal populations; however, the relationship was not significant. Future research should examine sex differences in carapace height and body volume which may more directly reflect selective pressures on female fecundity than straight-line shell lengths.
Although many reptiles, including tortoises, may be equipped morphologically to discriminate colors, there is very little experimental evidence that reptiles distinguish among hues and levels of saturation and brightness. Visual abilities or color (hue) discrimination have not been investigated for most tortoise species. In a behavioral experiment to test what visual cues are important, juvenile Leopard Tortoises (Stigmochelys pardalis) approached the colors red, light green, and olive most often, raising important questions regarding plant color and selection by Leopard Tortoises.