Distribution Of Tadpoles Research Articles

The agricultural transformation of Brazil’s Cerrado is influencing the diversity and distribution of tadpoles via lentification

The agricultural transformation of Brazil’s Cerrado is influencing the diversity and distribution of tadpoles via lentification

Selection of substrate type, substrate color, and vegetation by tadpoles of Dryophytes plicatus

The characteristics of microhabitats in streams can drive the distribution of tadpoles. We experimentally examined microhabitat selection of tadpoles of Dryophytes plicatus. We used a series of choice experiments to test if tadpoles had preferences for particular substrate types, substrate colors, and vegetation. Tadpoles of D. plicatus had a strong preference for mud substrates over sand, gravel, and rock substrates and preferred darker substrates over lighter substrates. Dryophytes plicatus tadpoles used the non-vegetated side of an aquarium more than the vegetated side. Our experimental results matched previous field observations in the case of the preference for mud substrates but differed from the field observations for substrate color and vegetation, suggesting that basic underlying preferences may be modified by various factors in nature or by learning or conditioning.

Spatial scale affects the importance of deterministic and stochastic factors in the structuring of tadpole assemblages in Brazilian Cerrado

Many factors influence the structure of natural assemblages. Species interaction and environmental factors may generate deterministic patterns, whereas dispersal and ecological drift may generate stochastic patterns. We used pond systems to understand how deterministic and stochastic factors interact and influence tadpole assemblages at different spatial scales. We used variation partitioning and a co-occurrence analysis to evaluate how local environment heterogeneity, species interaction, and spatial variables affected species composition at local and regional scales in Brazilian savanna. Both deterministic and stochastic processes were important to explain tadpole distribution at regional scale, but with a greater contribution of stochastic factors. At local scales, environmental and niche traits were more important to explain tadpole distribution into the habitats. We demonstrate that in Brazilian Cerrado, species composition can be explained by the "MacArthur paradox", in which niche processes are important at local scales, whereas dispersal constraints and population processes lead to stochastic patterns in species distribution at large spatial scales.

Atrazine contaminated sites and bullfrog tadpoles: evasive trends and biochemical consequences.

Atrazine (ATZ) is one of the most used active principles in agricultural systems. This pesticide has the ability to easily accumulate in terrestrial and aquatic environments, causing impacts with chronic adverse effects. Avoidance tests are tests that seek to assess the concentration from which a given organism escapes, that is, migrates to another habitat. They are being used as a modality of innovative and minimally invasive ecotoxicological tests. Our objective was to evaluate the sensitivity and possible toxic effects of ATZ in bullfrog tadpoles (Lithobates catesbeianus), through avoidance tests and oxidative stress analyses. We performed the behavioral avoidance test lasting 12 h, with observations every 60 min in a linear multi-compartment system with seven compartments. Each compartment corresponded to a concentration: negative control, 1, 2, 20, 200, 2000, 20,000 µg L-1. After the selection of habitat, organisms were forcedly maintained in the chosen concentrations for 48 h and then, metabolic effects were measured assessing the blood plasma amino acid profile and liver protein degradation. We also determined the effective concentrations of ATZ tested at 0 h and 48 h. The results showed that there was an effect of the treatment on the distribution of tadpoles, but not on the hours or on the combined effect (interaction). The biochemical analyses also showed a concentration-dependent relationship which caused significant toxic effects even in a short period of time. In conclusion, these frogs were able to avoid places with high concentrations of ATZ in the first hours of exposure, which suggests that in the natural environment these animals can migrate or avoid areas contaminated by this herbicide; however, depending on the selected concentration, serious biochemical consequences can occur.

Dichlorvos and Paraquat induced avoidance responses in tadpoles (Amietophrynus regularis reuss, 1833) and their contribution to population decline.

Pesticides notwithstanding their benefits in agriculture pose threats to non-target fauna such as amphibians. This study examined the avoidance responses of tadpoles of the African common toad, Amietophrynus regularis, exposed to Dichlorvos and Paraquat under a non-forced multi-compartmented exposure system (NFS) and estimated the Population Immediate Decline (PID) by integrating avoidance and lethal responses. The NFS was designed to allow the free movement of tadpoles across six compartments in order to elucidate the ability of aquatic organisms to detect and potentially avoid contaminated environments at will. The tadpoles (n=3 per compartment/concentration; 18 per system) were exposed to gradients of Dichlorvos (0, 0.3, 0.5, 0.7, 1.0 and 2.0 mg/L) and Paraquat (0, 1.0, 5.0, 10.0, 15.0, and 20.0 mg/L) in quadruplicates with their distribution recorded every 20 mins for 3 h. 48 h acute toxicity tests under forced exposure system (FS) was performed using the same range of concentrations. Acute toxicity (48 h) response in the FS tests was dose dependent with LC50 values of 0.79 mg/L and 6.46 mg/L recorded for Dichlorvos and Paraquat, respectively. The mean percentage distribution of tadpoles recorded for Dichlorvos and Paraquat was about 11% and 0% in the highest concentrations (2.0 and 20.0 mg/L) to 58% and 69% in compartments with no contaminants (control), respectively. PID was primarily driven by avoidance responses rather than mortality. These findings are of conservation interest as it elucidates the potential of both pesticides to impair local distribution of amphibians and cause biodiversity loss.

Environmental, spatial and biotic factors affect the tadpole distribution in Brazilian savannas

AbstractMultiple factors contribute to explaining the composition and structure of communities, and the niche is still the most used theory to describe how organisms interact with such factors to generate biological communities’ patterns. Both biotic and abiotic aspects of the environment along with the geographic space interact in complex ways with the behavior and physiological tolerance of organisms to structure a community. In this study, we tested the potential effects of the environment, space and competition and assess how the may determine the distribution of tadpoles in aquatic habitats located at Emas National Park. To this end, we sampled 23 aquatic habitats, described their environmental characteristics, recorded their geographic location, and carried out a survey of the tadpoles found. Later, we evaluated the effect of environmental and spatial variables on the distribution of species, through a Partial Redundancy analysis, using matrices of environmental descriptors and geographic location. We found that both environmental and spatial factors drive the distribution and the species composition of the studied assemblages. Also, when we analyzed the pattern of co‐occurrence, we observed that the number of co‐occurrence pairs of species in the Emas National Park is less frequent than expected by chance, suggesting that besides the effect of abiotic components (environmental and spatial factors), competition is a co‐structuring factor in the assemblages of tadpoles.Abstract in portuguese is available with online material.

Influence of microhabitat on the distribution of tadpoles of three endemic Nyctibatrachus species (Nyctibatrachidae) from the Western Ghats, India

AbstractAmphibians show a high amount of species richness and endemism. Such diversity can be attributed to their microenvironment as amphibians display fine‐scale heterogeneity depending on the microhabitats they inhabit. Tadpoles are considered as good indicators for understanding microhabitat–species association as they reflect the breeding sites and signify species survival potential. In this study, we assessed the microhabitat factors influencing the distribution of tadpoles of three endemic frogs of the genus Nyctibatrachus namely N. jog, N. kempholeyensis, and N. kumbara from central Western Ghats, India. Forty‐three streams were sampled from three river basins, and stream characteristics were analyzed using generalized linear models. The results indicate that the tadpoles show specific microhabitat preferences and spatial niche partitioning. Among microhabitat variables, the slope significantly influenced the distribution of tadpoles of N. jog and N. kempholeyensis. The tadpoles of N. jog preferred steep slopes, while N. kempholeyensis tadpoles were found in gradual slopes with low water depth. For N. kumbara tadpoles, water temperature significantly influenced their distribution in the streams. Such spatial heterogeneity promotes the coexistence of these species supporting the niche theory. The study advances the understanding of how amphibian diversity from the Western Ghats is shaped at the microhabitat scale. The perennial streams that the Nyctibatrachus tadpoles inhabit are at risk due to anthropogenic activities. The findings of this study provide important baseline data that could be useful for the conservation of the endemic anurans in the Western Ghats, India.

Reproductive phenology of the American Bullfrog in subtropical Brazil: photoperiod as a main determinant of seasonal activity.

The North American bullfrog Lithobates catesbeianus continues to invade ecosystems worldwide, potentially causing population declines and even extinctions. Within its native distribution, bullfrogs show prolonged reproductive seasons and high fertility. However, data on breeding biology of bullfrogs ex-situ in invaded localities mainly comes from anecdotal reports. Understanding how invasive species are adjusting their life histories to new colonized environments is important for conservation purposes. Here we describe temporal and spatial abundance, calling activity, spawning and tadpole distribution of bullfrogs in southern Brazil. Eighteen samplings occurred during one year. The abundance of individuals was positively related to longer photoperiods and higher temperatures. Reproductive activity was also positively associated with longer photoperiods. Calling sites, spawning and tadpoles were associated with microhabitats presenting hydrophytes, which may provide shelter and thermal stability to bullfrogs. The reproductive seasonal activity of bullfrogs can be highly variable across its growing geographical range, but in subtropical Brazil it is associated with photoperiod, a highly predictable abiotic determinant. In our study area, bullfrogs presented a breeding season twice as long as that observed in some native localities. We suggest that management strategies directed to bullfrog populations must consider the habitat structures and seasonal regimes determined by each invaded environment.

Effects of Salinity and Density on Tadpoles of Two Anurans from the Río Salado, Puebla, Mexico

Abstract Numerous studies have explored environmental factors that drive the distributions of anuran larvae. However, the causal links between physical or chemical factors and tadpole distributions often remain untested. The Rio Salado is an intermittent, naturally saline river in Puebla, Mexico, that is increasingly being impacted by removal of water for commercial salt production. Using tadpoles of Exerodonta xera (Hylidae; Puebla Treefrog) and Incilius occidentalis (Bufonidae; Pine Toad), we experimentally examined the hypothesis that the distribution of tadpoles along the Rio Salado results from the effects of salinity on tadpole survivorship, growth, and metamorphosis. We also examined the effect of tadpole density and the interaction of tadpole density and salinity, because pool size likely affects tadpole density. Increased salinity did not affect survivorship in I. occidentalis but reduced survivorship in E. xera by approximately 20% at both 0.4 parts per thousand (ppt) (0.4 g L−1) and 0.8 ppt (0....

Temporal distribution and age structure of tadpoles of Hypsiboas faber and H. leptolineatus in ponds: how do they coexist?

According to the theory of limiting similarity, two closely similar species that compete for resources can coexist when the ratio of the sizes of their trophic apparatus is approximately 1.3. In this study, we investigated how two similar tadpole forms coexist. We described the temporal distribution of the tadpoles of Hypsiboas faber and H. leptolineatus in ponds during the course of one year, detailing the respective age structures (Gosner stages and size). We also estimated total length ratios. The larger-sized species, H. faber, entered the ponds earlier in the year, which might give it some advantage in resource exploitation and favour the maintenance of the size difference between the species. The size difference may lead to a difference in microhabitat utilization and/or modify resource preferences, thus allowing the two species to coexist.

Population dynamics of tadpoles of Crossodactylus gaudichaudii (Anura: Hylodidae) in the Atlantic Rainforest of Ilha Grande, southeastern Brazil

We studied the temporal distribution of tadpoles of Crossodactylus gaudichaudii, and their relationship with rainfall, in a Brazilian Atlantic Rainforest area. There is no previous information about the population dynamics of tadpoles from this species. We sampled 60 m along streams between May 2002 and April 2005. Tadpoles in initial stages of development (up to stage 25) were present in all months of the year and represented 80.4% of those sampled. This indicates a continuous recruitment of new individuals in the aquatic environment. Tadpoles in final stages of development (stages 42–46) represented only 5% of those sampled, which may be the result of higher mortality in the early development stages. Body length of tadpoles varied among developmental stages and between seasons. Tadpole density was higher in the rainy season than in the dry season, and was significantly related to rainfall in the area.

Spatial and temporal distribution of tadpole assemblages (Amphibia, Anura) in a seasonal dry tropical forest of southeastern Brazil

We determined spatial and temporal distribution of tadpoles in 11 breeding habitats from Morro do Diabo State Park (MDSP), southeastern Brazil. Breeding habitats occupancy by tadpoles was tested to be different from a null model of random placement of species. We also tested whether tadpole occupancy in a given breeding habitat is organized according to different ecomorphological guilds, and we analyzed spatial partitioning of tadpoles among breeding habitats through similarity analysis. For temporal analysis we analyzed temporal partitioning of tadpole monthly occurrence also using similarity analysis, and assessed what climatic variable better predicts tadpole temporal occurrence in the MDSP, through regression analysis. Among tadpoles from 19 anuran species, distribution was different from a null model, but co-occurrence patterns among the breeding habitats did not differ among different guilds. However, breeding habitats with similar hydroperiods had similar species composition, which may be related to the reproduction patterns of species. Among the three climatic variables analyzed (rainfall, temperature, and photoperiod), temporal occurrence of monthly tadpole richness and abundance was correlated with temperature and rainfall. Most species were found only during the rainy season months, and overlap occurred within three groups of species. Thus, temporal distribution does not seem to be an important mechanism in species segregation at the MDSP, where the dry season is pronounced. In this case, spatial partitioning tends to be more important for species coexistence.

Distribution of tadpoles of Ollotis occidentalis (Amphibia: Anura: Bufonidae) along the Río Salado, Puebla, México

We examined monthly variation in the characteristics of river sections along the Rio Salado (Puebla, Mexico) and how these factors were associated with the dis- tribution of the tadpoles of the toad Ollotis occidentalis . Tadpoles were observed in the river in March 2007, and from November 2007 through February 2008 and were only found in the main river channel. Sections of the Rio Salado with tadpoles were deeper, wider, and longer than sections without tadpoles. Dissolved oxygen levels were higher and salinity was lower in river sections with tadpoles compared to the sections without tadpoles. There was no difference in temperature between sections with and without tadpoles. Tadpoles were found in river sections that contained more vegeta- tion than river section without tadpoles. Our results suggest that the distribution of tadpoles of O. occidentalis is related to the permanence of water, the chemical nature of the water, and the presence of vegetation.

Distribution of tadpoles of large wrinkled frog Nyctibatrachus major in central Western Ghats: influence of habitat variables

The relationship between habitat variables and the distribution and abundance of adults and tadpoles of Nyctibatrachus major (large wrinkled frog) in 35 forest streams in central Western Ghats is detailed in this paper. Tadpoles were not equally distributed among these streams. Adult frogs and tadpoles were absent from 19 streams. In the remaining 16 streams, adults were found throughout the study period but the density of tadpoles varied considerably. Analysis of habitat variables at streams showed significant relationship with canopy cover over the streams, presence of leaf litter and high relative humidity on the occurrence of tadpoles. Reduction in canopy cover increases light level and air and water temperature of the streams discouraging the occurrence of adult frogs and tadpoles. However, canopy cover in the study area is frequently altered by agriculture related human activities including removal of trees for fuel and timber, pruning of green leaves and twigs for making manure and conversion of forest into commercial plantations. The results suggest that disturbances to forest canopy near streams could have deleterious effects on the occurrence and distribution of tadpoles.

Época reproductiva y distribución geográfica del sapo Incilius aucoinae (Bufonidae) en Golfito, Costa Rica

Reproductive period and geographic distribution of the toad Incilius aucoinae in Golfito, Costa Rica. The biology of neotropical amphibians is not well known. Some toad species of the Bufonidae family are common, thus allowing the study of their populations. We studied a population in rio Canaza, Golfito, Costa Rica, in a sector 360 m upstream of Barrio Urena, divided in 36 sectors of 10 m. The study was carried out for five years, but taking samples of adults in January 1995, 1997, 1998 (except March), and 1999. We also studied tadpoles during four days in 1997. In total, 443 males and 7 females were marked, with 315 males recaptured and no females. Females are bigger (91.1 mm) than males (61.3 mm). Most recaptured individuals occurred in the same or adjacent sectors, with a maximum movement of 28 sectors. One individual was recaptured repeatedly in all the samples. This indicates that they survived at least five reproductive cycles. The reproductive cycle takes place during the dry season, between December and April. We found more individuals during the reproductive cycle of 1997 and less during 1995. Sector 6 had the most number of males and sector number 4 had the least. Sectors with semi-open vegetation had more males compared to sectors with more forest cover. February is the month with the highest abundance of males. There are intermediate values in December and January, and fewer individuals in March and April. In every month, except February, the abundance of individuals was greater where there were beaches. Tadpoles were found both during the day and night in the 31 river sectors, but it was less likely to find tadpoles in the river section during the night. During the day all tadpoles were found scattered around the river, at night they congregated near river margins. The reproductive cycle of this toad occurs during the dry season and females are present only in the reproductive season, resulting in an almost only male sex ratio (only seven females were found). Males can reproduce at least in 5 reproductive cycles, and -unexpectedly- day and night distribution of tadpoles varies. Rev. Biol. Trop. 57 (Suppl. 1): 301-311. Epub 2009 November 30.

Redescription of the tadpole of Leptodactylus rhodomystax (Anura: Leptodactylidae) with natural history notes

The tadpole of Leptodactylus rhodomystax is described based on individuals in several stages of development. We compare them with other tadpoles of the Leptodactylus pentadactylus group and three other sympatric species with similar morphology and color patterns. We also provide comments on spawning sites, clutch size, and the distribution of tadpoles in ponds located in a 64 km 2 study area. The tadpole of L. rhodomystax differs from all species of the L. pentadactylus group (except L. flavopictus) in total length and in having uniform black color. It differs in relation to the LTRF (2(2)/3) of all species except L. lithonaetes and L. rhodonotus. Leptodactylus rhodomystax is generally only found in the western watershed of our study area. Foam nests were deposited between shrubs, roots, and fallen tree trunks near temporary ponds. Tadpoles were free-swimming, benthic, and found in the leaf litter of ponds between January and May. The tadpoles are intraand inter-specific predators of anuran eggs and tadpoles.

DISTRIBUTION OF TADPOLES WITHIN AND AMONG BRAZILIAN STREAMS: THE INFLUENCE OF PREDATORS, HABITAT SIZE AND HETEROGENEITY

We studied the composition and richness of local tadpole assemblages in several streams at a forest site in southeastern Brazil. We initially focused on species distributions within streams, comparing the relative availability of microhabitats with the relative use of each microhabitat type by tadpoles of different species, in order to assess the existence of preference patterns. Then we assessed the role of features assumed to influence species distributions among streams, which may influence breeding site selection by adult frogs and, consequently, tadpole distribution. These features were stream size, tadpole predator abundance, structure of marginal vegetation, and microhabitat availability for tadpoles. We looked for gradients of species richness along gradients of the variables noticed to influence tadpole assemblage composition. Tadpoles of all species showed selectivity in microhabitat use. Species distribution among streams was influenced mostly by number of potential tadpole predators present, stream volume, arboreal vegetation cover at stream margins, and tadpole microhabitat diversity, though only the first two variables accounted for gradients in species richness. Even though smaller streams tend to shelter more anuran species than larger ones at sites in southeastern Brazil, we recommend the conservation of streams of a range of sizes and structural features, since anuran assemblages associated with streams vary in species composition along gradients in these characteristics.

THERMAL TOLERANCE AND THERMOREGULATION BY TAIWANESE RHACOPHORID TADPOLES (BUERGERIA JAPONICA) LIVING IN GEOTHERMAL HOT SPRINGS AND STREAMS

We measured the critical thermal maxima (CTMax) of tadpoles of Buergeria japonica inhabiting streams and geothermal hot springs. The CTMax of all B. japonica tadpoles was over 41 C, indicating that the tadpoles are heat-tolerant. At Rushan, we monitored the temporal and spatial distribution of tadpoles over a 24-h period in a 220 cm × 70 cm plot that is fed by a geothermal hot spring. The thermal profiles of the plot varied seasonally, but the highest water temperature selected by tadpoles remained similar (ca. 37 C). In the winter, the thermal range of the plot was lower (29.5–40.6 C), and tadpoles could be found in the majority of the plot. In contrast, during the spring and summer the temperature ranges of the plot were higher (33.1–43.8 C and 33.0–42.4 C, respectively), and tadpoles could be found only in the cooler sections of the plot, especially around 1000 h with direct solar radiation. These results suggest that extreme heat tolerance and behavioral thermoregulation (i.e., heat avoidance behavior) are the main means by which B. japonica tadpoles cope with the high temperatures in geothermal hot springs.

Mechanism of food detection in the tadpoles of the bronze frog Rana temporalis

Mechanism of food detection in Rana temporalis tadpoles was studied using a rectangular choice tank with end compartments (stimulus zones) providing exclusively visual and/or chemical food cues. Boiled spinach served as the food. The test tadpoles were starved for 24 h before use. They were released from the center of the choice tank (n=24) after 5 min of acclimation to test for end bias and food-detecting mechanism. The number of tadpoles in the two stimulus zones was recorded at 5-min intervals from 10 to 30 min. In the end-bias tests (without food cues) tadpole distribution was comparable at all times in the two compartments of the choice tank, exhibiting no end bias. In tests with the visual food cues provided in one of the stimulus zones, the tadpole distribution was also random. On the other hand, in experiments involving chemical cues emanating from food the tadpoles preferentially associated with the food source in significantly greater numbers compared to the zone lacking food or providing only a visual cue. The experiments with individual test tadpoles also revealed that they detect food based on chemical cues and ruled out “copycat” behavior. These findings on R. temporalis tadpoles reveal that chemical senses predominate over the visual senses in detection of food and foraging.

Risk of predation affects aggregation size: a study with tadpoles of Phrynomantis microps (Anura: Microhylidae)

Tadpoles of the microhylid frog Phrynomantis microps form swarms near the water surface of savannah ponds during the day. Observations of tadpole distribution at night showed that these aggregations disappear and that tadpoles instead swim in a random distribution near the water surface. The clarity of pond water had significant effects on the distribution of tadpoles during the day. The size of aggregations, and the densities of tadpoles within them, both increased with increasing water clarity. Since tadpoles of this species are known to aggregate in response to visually hunting aquatic predators, these results suggest that tadpoles respond to high water clarity as an indicator of increased predation risk. This supports the hypothesis that, under conditions of increasing predation risk, animals should form larger and more dense groups up to a critical group size. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.