Grass Frog Research Articles

Translocation of the threatened Growling Grass FrogLitoria raniformis: a case study

Translocation is occasionally suggested as a last resort strategy for dealing with ‘unavoidable’ loss of Growling Grass Frog Litoria raniformis habitat in urbanising landscapes. However, examples of attempts to translocate an entire population of L. raniformis are rare and their success (or lack of success) is poorly documented in the literature. In this study, we detail the translocation of a population of L. raniformis from a farm dam being destroyed for residential development to a purpose-built wetland 480 m away.The population was translocated between November 2010 and May 2011. We used mark-recapture to estimate the number of frogs in the population prior to translocation. Visual counts of L. raniformis at the dam indicated a maximum of 39 adult frogs to be present while 355 frogs were marked over the course of a single season (November 2010 to March 2011).Translocation of 156 frogs and unassisted colonisation by 32 frogs resulted in an estimated 70% of adults marked at the dam moving to the wetland...

Новый способ регистрации механической работы изолированного нефиксированного сердца лягушки

The purpose of article was a presentation of the new method for mechanical work registration of an isolated non-fixed frog heart, based on dynamic determining of its bio-impedance with possibility of simultaneous ECG registration. During experiments the bio-impedance of a grass frog heart (Rana temporaria) placed in Ringer solution for coldblooded animals have been determined continually by using of the computer reographic apparatus “Reospectrum” (“Neurosoft”, Russia). For proving of the method sensitivity was performed stimulation of a heart by adrenalin in all experiments (n=10). The results were illustrated by both impedance-cardiogram (ICG) and electrocardiogram fragments recorded synchronously. It have been established that in 4 min after hormone application the heart rate rises in 50-70%. The highest rate usually was observed in 6-8 min after stimulation by adrenalin. After 8 min the heart rate became 2.5 times faster than initial parameter. “Amplitude” of contractions changes in phase too. The largest positive inotropic effect of adrenalin was observed in 4-5 min – the amplitude of ICG waves increase in 126.6% in comparison with initial point. After amplitude peak the significant decrease of waves was registered in 14-16 min after the application in comparison with initial parameter. The main technical achievement of the method for mechanical work registration of isolated heart is possibility to obtain required data characterized contractile activity of different arias of frog heart muscle easily and simply without risk of myocardium injure.

Correlation of neural responses in the cochlear nucleus with low-frequency noise amplitude modulation of a tonal signal

The responses of single neurons of the cochlear nucleus of a grass frog to long tonal signals amplitude-modulated by repeat intervals of low-frequency noise have been studied. The carrier frequency always corresponded to the characteristic frequency of the studied cell (a range of 0.2 kHz–2 kHz); the modulated signal was noise in the ranges 0–15 Hz, 0–50 Hz, or 0–150 Hz. We obtained the correlation functions of the cyclic histogram reflecting the change in probability of a neuron pulse discharge (spike) during the modulation period with the shape of the signal envelope in the same period. The form of the obtained correlation functions usually does not change qualitatively with a change in carrier level or modulation depth; however, this could essentially depend of the frequency component of the modulating function. In the majority of cases, comparison of the cyclic histogram of the reaction with only the current amplitude value does not adequately reveal the signal’s time features that determine the reaction of a neuron. The response is also determined by the other sound features, primarily by the rate of the change in amplitude. The studied neurons differed among themselves, both in preference toward a certain range of modulated frequencies and in the features of the envelope that caused the cell’s response.

EVALUATION OF CARDIOTONIC ACTION OF ETHANOL EXTRACT OF LAGENARIA SICERARIA PULP ON FROG’S HEART

The aim of this study is to the Herbal remedies are used worldwide for various diseases. They are safer and less expensive with lesser side effects than synthetic drugs. Lagenaria siceraria , the vegetable gou rd, belonging to the family Cucurbitaceae is used as diuretic, cardio - tonic, cardio - protective and nutritive agent and traditionally in the treatment of jaundice, diabetes, ulcer, piles, colitis, insanity, hypertens ion, congestive cardiac failure and skin diseases. The present study was carried out to evaluate the cardiotonic effect of ethanol extract of pulp of Lagenaria siceraria (EE L S P ) in Amphibians such as the grass frog Rana pipiensin . After toxicity evaluation in albino rats two doses of the ethanol extract of Lagenaria siceraria pulp extracted with 90 % methanol using a Soxhelts apparatus was selected for the experiment. One grass Rana pipiensin frogs were taken and double pitching was done. Frog heart in situ was setup following standard procedures. Frog’s ringer, Acetyl choline , Adrenalin and ¼ th Ca followed by two doses of EE L S P was given one after the one and the graphing was recorded. The extract at 400 mg and 80 0 mg produced significant cardiotonic action. Thus the study elucidates that ethanol extract of Lagenaria siceraria pulp possess cardiotonic action at the doses of 400 and 800 mg .

Wetland characteristics influence disease risk for a threatened amphibian.

Identifying determinants of the probability and intensity of infections is important for understanding the epidemiology of wildlife diseases, and for managing their impact on threatened species. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis, has decimated populations of some amphibians. However, recent studies have identified important environmental constraints on the disease, related to the pathogen's physiological tolerances. In this study, we identified several intrinsic and extrinsic determinants of the probability and intensity of chytrid infections for the threatened growling grass frog (Litoria raniformis) in southeastern Australia, and used mark-recapture to estimate the effect of chytrid infections on the probability of survival of these frogs. Water temperature and salinity had negative effects on both the probability and intensity of chytrid infections. We coupled models of the infection process with a model of the effect of chytrid infections on the probability of survival to assess variation in the impact of chytridiomycosis between wetlands with differing temperature and salinity profiles. Our results suggest that warm, saline wetlands may be refuges from chytridiomycosis for L. raniformis, and should be priorities for protection. Our results also suggest that management actions that increase water temperature (e.g., reducing canopy shading) and salinity (e.g., complementing inflows with groundwater) could be trialed to reduce the impacts of chytridiomycosis on this species. This and other recent studies highlight the value of research on environmental risk factors for chytridiomycosis.

Dependence of Variability of Neuronal Responses in the Frog Torus Semicircularis on the Parameters of Acoustic Stimuli

Responses of neurons of various sensory nuclei to presentation of specific stimuli can be characterized not only by the mean number of action potentials (APs) in such reactions and the pattern of AP time distribution, but also by the level of repeatability of the reaction. We studied impulse responses of neurons localized in the auditory center of the midbrain of the grass frog under the action of tone segments of a characteristic frequency, with an unmodulated or modulated amplitude. The repeatability of reactions was evaluated according to the ratio between the variation of the number of APs to presentations of the signal and the mean number of APs in the response (Fano factor). Neurons differed noticeably from each other in this characteristic. In the studied sampling, we observed no close correlation between the Fano factor and the mean number of APs in the response, although in some cells such correlation may appear rather significant. In the case of the action of low-intensity signals, an increase in the intensity resulted, on average, in the improvement of repeatability of the reaction; with higher levels of the signal, this trend, however, was not maintained. Complication of the signal using amplitude modulation usually caused a decrease in the variability, although in some cells the pattern of such dependence was opposite. We found a trend toward a rise in the Fano factor with increase in the duration of the time interval of observation. We focus our attention on the correlation between stochastic reactions of separate cells of sensory systems and variability of responses of the entire organism at fixed sensory stimulations.

Spectrochemical and histochemical analyses of tissues of grass frog and gray toad tadpoles developing under simulation of pollution by plumbum and ferrum

Visual, spectrochemical, and histochemical analyses of tadpoles of two tailless amphibian species (Rana temporaria L. and Bufo bufo L) developed under simulation of water pollution by plumbum and ferruginous alloys demonstrated an alimentary way of the delivery of these metal ions in the organism. Accumulation of these metal ions occurs in intestine and liver tissues and increases with the development.

A Bayesian model of metapopulation viability, with application to an endangered amphibian

AbstractAimPopulation viability analysis (PVA) is used to quantify the risks faced by species under alternative management regimes. BayesianPVAs allow uncertainty in the parameters of the underlying population model to be easily propagated through to the predictions. We developed a Bayesian stochastic patch occupancy model (SPOM) and used this model to assess the viability of a metapopulation of the growling grass frog (Litoria raniformis) under different urbanization scenarios.LocationMelbourne, Victoria, Australia.MethodsWe fitted a Bayesian model that accounted for imperfect detection to a multiseason occupancy dataset forL. raniformiscollected across northern Melbourne. The probability of extinction was modelled as a function of effective wetland area, aquatic vegetation cover and connectivity, using logistic regression. The probability of colonization was modelled as a function of connectivity alone. We then simulated the dynamics of a metapopulation ofL. raniformissubject to differing levels of urbanization and compensatory wetland creation. Uncertainty was propagated by conducting simulations for 5000 estimates of the parameters of the models for extinction and colonization.ResultsThere was considerable uncertainty in both the probability of quasi‐extinction and the minimum number of occupied wetlands under most urbanization scenarios. Uncertainty around the change in quasi‐extinction risk and minimum metapopulation size increased with increasing habitat loss. For our focal metapopulation, the analysis revealed that significant investment in new wetlands may be required to offset the impacts of urbanization.Main conclusionsBayesian approaches toPVAallow parametric uncertainty to be propagated and considered in management decisions. They also provide means of identifying parameters that represent critical uncertainties, and, through the use of informative priors, can easily assimilate new data to reduce parametric uncertainty. These advantages, and the ready availability of software to run Bayesian analyses, will ensure that Bayesian approaches are used increasingly forPVAs.

A Stockpile of Ova in the Grass Frog Rana temporaria is Established Once for the Life Span. Do Ovaries in Amphibians and in Mammals Follow the Same Evolutionary Strategy?

Most anuran amphibians produce high numbers of eggs during several consecutive breeding seasons. The question is still open whether oocytes are formed anew as a result of oogonial proliferation after each spawning or the definitive pool of oocytes is established during the juvenile period and is sufficient for the whole reproductive life span of a female. Our quantitative studies show that primary oogonia in adult female frogs can proliferate, but they fail to differentiate further and do not enter meiosis, and thereby there is no supplementation of new generations of oocytes after each spawning. Ovaries of one-year-old grass frogs contain (median) 53,447 diplotene oocytes, in two-years-old frogs this number decreased to 33,583 and eventually reached 25,679 in virgin mature females. More than 50% decrease in the total oocyte number was accompanied by massive degeneration (atresia) of oocytes. The final number of oocytes in a female forms a stock for 11-12 breeding seasons and exceeds the number of eggs produced during the potential reproductive life span of this species. The phylogenetic context of oocyte recruitment modes in the major clades of vertebrates is discussed in respect to their ability to replenish the stock (a renewable stock in ovaries named "open" vs. a non-renewable stock in ovaries named "closed").

Characteristics of refugia used by the threatened Australian growling grass frog (Litoria raniformis) during a prolonged drought

Context Because they are dependent on water, drought can have a deleterious impact on aquatic-breeding amphibians. One such species, the threatened growling grass frog (Litoria raniformis) occurs in south-eastern Australia, a region that has recently emerged from a decade-long, severe drought. Aims We aimed to identify features of drought refugia that facilitate persistence of L. raniformis, so as to provide guidance to natural-resource managers attempting to conserve populations of this species during drought. Methods We conducted repeat surveys for L. raniformis at 90 water bodies at the end of the ‘millennium drought’. We recorded the following six environmental variables for each water body: origin (natural or not), type (lotic or lentic), proportion of aquatic vegetation cover, conductivity of water, riparian tree-canopy cover and distance to the nearest woodland. We used occupancy models to relate the presence of L. raniformis to these variables, while accounting for uncertain detection. Key results Water-body type (natural or artificial, lentic or lotic) had minimal influence on the probability of occupancy by L. raniformis. We found a strong negative relationship between occupancy and conductivity of water (a surrogate for salinity), and a positive relationship between occupancy and the proportion of aquatic vegetation. We found a negative relationship between detection and the extent of aquatic vegetation, and a mildly negative effect of canopy cover on occupancy. Conclusions Habitat characteristics are more important indicators of the quality of drought refugia for L. raniformis than is the type of water body per se. Consequently, we identified aquatic vegetation and salinity as important targets for management when planning the retention, creation or restoration of habitat to facilitate persistence of L. raniformis during drought. Implications Our results highlighted aquatic vegetation and water-quality parameters that are likely to facilitate the persistence of L. raniformis during drought. Assessing the effectiveness of our recommendations in an experimental framework would ensure that conservation management of this frog can be refined over time.

Adaptation of differential sensitivity of auditory system neurons to amplitude modulation after abrupt change of signal level

Impulse activity of neurons of brainstem auditory nuclei (medulla dorsal nucleus and midbrain torus semicircularis) of the grass frog (Rana temporaria) was recorded under action of long amplitude-modulated tonal signals. After adaptation of neuronal response to acting stimulus (30–60 s after its onset), we performed a sharp change (by 20–40 dB) of the mean signal level with preservation of unchanged frequency and depth of modulation. We also recorded a change of density impulsation and of degree of its synchronization with the modulation period as well as the phase of maximum reaction at the modulation period and phase of the response every 2 or 4 s. In the adapted state, the sharp change of the mean level had been provided, while maintaining frequency and depth unchanged. During the adaptation to long signals with small modulation indexes the firing rate continuously decreased, but synchronization with envelope usually increased considerably. A sharp rise in the mean level resulted in an increase of firing rate, which could be accompanied either by a continuation of synchronization growth (the effect is more typical of the dorsal nucleus) or by a sharp fall in synchrony with its subsequent slow recovery (the effect is more typical of the torus semicircularis). Nature of the changes following the change of the intensity of the reaction could depend on the signal parameters (initial level, magnitude of the jump, frequency and depth of modulation). The connection between the observed physiological data and the psychophysics of differential intensity coding is discussed.

Structure and fragmentation of growling grass frog metapopulations

Metapopulations occur in fragmented landscapes, and consist of demographically-independent populations connected by dispersal. Nevertheless, anthropogenic habitat fragmentation may be fatal to metapopulations, as it disrupts dispersal and gene flow, and undermines the balance between population extinction and colonization. Understanding the extent to which particular land-use practices disrupt dispersal and gene flow is therefore crucial for conserving metapopulations. We examined the structure and fragmentation of metapopulations of the endangered growling grass frog (Litoria raniformis) in an urbanizing landscape in southern Australia. Population clustering analyses revealed three distinct genetic units, corresponding to the three wetland clusters sampled. Isolation-by-distance was apparent between populations, and genetic distance was significantly correlated with the presence of urban barriers between populations. Our study provides evidence that urbanization fragments metapopulations of L. raniformis. Managers of L. raniformis in urbanizing landscapes should seek to mitigate effects of urbanization on dispersal and gene flow.

Heavy metal pollution negatively correlates with anuran species richness and distribution in south‐eastern Australia

AbstractHeavy metal pollution has likely played an important role in global biodiversity decline, but there remains a paucity of information concerning the effects of metals on amphibian diversity. This study assessed anuran species richness and distribution in relation to sediment metal content and water chemistry in wetlands located along the Merri Creek corridor in Victoria, south‐eastern Australia. Anurans were present in 60% (21/35) of study sites, with a total of six species detected: the eastern common froglet (Crinia signifera), the eastern sign‐bearing froglet (Crinia parinsignifera), the southern brown tree frog (Litoria ewingii), the growling grass frog (Litoria raniformis), the eastern banjo frog (Limnodynastes dumerilii) and the spotted marsh frog (Limnodynastes tasmaniensis). Mean species richness was 1.77 ± 0.32 per site, and species richness ranged from zero to six species per site. Across sites, species richness correlated negatively with sediment concentrations of six heavy metals: copper, nickel, lead, zinc, cadmium and mercury. Species richness also correlated negatively with wetland water electrical conductivity (a proxy for salinity) and concentrations of orthophosphate. Distributions of the three most commonly observed frog species (C. signifera, L. tasmaniensis and L. ewingii) were significantly negatively associated with the total level of metal contamination at individual sites. The study is the first to provide evidence for an association between metal contamination and anuran species richness and distribution in the southern hemisphere, adding to a small but growing body of evidence that heavy metal pollution has contributed to global amphibian decline.

Urbanization interferes with the use of amphibians as indicators of ecological integrity of wetlands.

Summary 1. Wetlands are ecologically and economically important ecosystems but are threatened globally by many forms of human disturbance. Understanding the responses of wetland species to human disturbance is essential for effective wetland management and conservation. 2. We undertook a study to determine (i) whether anurans can be used effectively to assess the ecological integrity of wetlands affected by groundwater withdrawal and, if so, (ii) what effect increasing urbanization might have on the utility of anurans as wetland indicators. We monitored the intensity of anuran calls at 42 wetlands in south‐western Florida throughout 2001–2002 and 2005–2009. 3. We first validated the use of anurans to assess wetland integrity using a small group of wetlands by comparing anuran calling and subsequent tadpole development with an established index employing vegetation composition and structure. We then verified that the results could be expanded to a variety of sites throughout the region. Finally, we focused on urbanized wetlands to determine whether urbanization could interfere with the use of anurans to assess wetland integrity. 4. We used PRESENCE to estimate occupancy and detection probabilities and to examine the relationship between occupancy and five covariates expected to influence individual species occurrence. We used FRAGSTATS to calculate the mean proximity index for urbanized wetlands, which assesses the size and distribution of land use types within a specified area. 5. Our results showed that the group of species including oak toad Anaxyrus quercicus, southern cricket frog Acris gryllus, pinewoods treefrog Hyla femoralis, barking treefrog Hyla gratiosa, and little grass frog Pseudacris ocularis is a reliable indicator of wetland integrity. However, this same group of species, which is sensitive to wetland health, is selectively excluded from urbanized wetlands. 6. Synthesis and applications. Although anurans are effective indicators of wetland health and complement vegetation surveys, the usefulness of this group for monitoring the ecological integrity of wetlands can be substantially reduced, or eliminated, as a consequence of urbanization. We urge for careful consideration of confounding factors in any studies examining the utility of indicator species.

A new cryptic species of the genus Eleutherodactylus (Amphibia: Anura: Eleutherodactylidae) from Cuba

The widely distributed grass frog of Cuba, Eleutherodactylus varleyi, is shown here to comprise two species. One, E. var-leyi, occurs in western and central Cuba while the other, E. feichtingeri n. sp., occurs in central and eastern Cuba. The twospecies are sympatric in central Cuba, and syntopic in the vicinity of Sierra de Cubitas, Camagüey Province. A molecularphylogeny of mitochondrial DNA sequences from 18 localities confirms the existence of two well-supported major cladescorresponding to each of these species, and the sympatry of the species. Tympanum size and advertisement call are themost useful diagnostic characters, although the two species are shown to have karyotypic differences as well. Possible character displacement in morphology and vocalization, in the area of sympatry, is discussed.

Classical metapopulation theory as a useful paradigm for the conservation of an endangered amphibian

Classical metapopulation theory (CMT) has proven an attractive paradigm for ecologists concerned with the conservation of aquatic-breeding amphibians, given its apparent fit with the population dynamics of these animals, and the opportunities the concept provides to assess alternate management options. Nevertheless, several authors have cautioned against uncritical application of this paradigm. We assessed the application of CMT to the conservation of the endangered growling grass frog (Litoria raniformis) in the urbanising landscapes of Melbourne, Victoria, Australia. Support for five predictions developed from the basic tenets of CMT was assessed using a multi-year occupancy and mark–recapture data-set. There was congruence between all five predictions and data. Wetland occupancy was strongly influenced by the proximity of neighbouring populations (‘connectivity’), but the estimated rate of dispersal between wetlands was low. Wetland occupancy was also temporally dynamic, with only a weak effect of connectivity on the probability of extinction, but a strong positive influence of connectivity on the probability of colonisation. Our work confirms that CMT provides a useful model of the dynamics of L. raniformis in urbanising landscapes, and justifies the application of the paradigm to conservation planning for this species. We argue that CMT may prove relevant to numerous aquatic-breeding amphibians, and encourage assessment of the application of CMT to the conservation of these animals.

Cellular and Network Contributions to Vestibular Signal Processing: Impact of Ion Conductances, Synaptic Inhibition, and Noise

Head motion-related sensory signals are transformed by second-order vestibular neurons (2°VNs) into appropriate commands for retinal image stabilization during body motion. In frogs, these 2°VNs form two distinct subpopulations that have either tonic or highly phasic intrinsic properties, essentially compatible with low-pass and bandpass filter characteristics, respectively. In the present study, physiological data on cellular properties of 2°VNs of the grass frog (Rana temporaria) have been used to construct conductance-based spiking cellular models that were fine-tuned by fitting to recorded spike-frequency data. The results of this approach suggest that low-threshold, voltage-dependent potassium channels in phasic and spike-dependent potassium channels in tonic 2°VNs are important contributors to the differential, yet complementary response characteristics of the two vestibular subtypes. Extension of the cellular model with conductance-based synapses allowed simulation of afferent excitation and evaluation of the emerging properties of local feedforward inhibitory circuits. This approach revealed the relative contributions of intrinsic and synaptic factors on afferent signal processing in phasic 2°VNs. Additional extension of the single-cell model to a population model allowed testing under more natural conditions including asynchronous afferent labyrinthine input and synaptic noise. This latter approach indicated that the feedforward inhibition from the local inhibitory network acts as a high-pass filter, which reinforces the impact of the intrinsic membrane properties of phasic 2°VNs on peak response amplitude and timing. Thus, the combination of cellular and network properties enables phasic 2°VNs to work as a noise-resistant detector, suitable for central processing of short-duration vestibular signals.

Microsatellite loci for the endangered growling grass frog (Litoria raniformis), with cross amplification in other Australian frog species

The growling grass frog, Litoria raniformis, was once abundant in south-eastern Australia but has suffered severe declines over the past 20 years. Here we describe nine polymorphic microsatellite loci for L. raniformis. Genetic variation was assessed in 59 individuals from Somerton, Victoria in south-eastern Australia. The number of alleles per locus ranged from three to 16. Cross amplification was assessed in ten other Australian hylid frogs. These microsatellite markers will be used to investigate impacts of urbanization on dispersal and gene flow in L. raniformis.

Frog oocyte in vitro maturation test as a method to investigate Ni2+ toxicity

Frog oocyte in vitro maturation test as a method to investigate Ni2+ toxicity The ability of gonadotropic hormone (GTH) of sturgeon fish Acipenser göldenstödti Br. to initiate a specific stimulatory effect on grass frog Rana temporaria L. oocytes, producing its in vitro maturation, was employed as a method to investigate the effect of nickel ion concentration on test oocytes in a highly sensitive test system, "Oocyte-GTH". Oocytes of four frogs with different hormone sensitivity were used in the investigation. It was shown that Ni2+ at a concentration of 0.1 mg/L produced a considerable stimulatory effect only in test frog oocytes with low hormonal sensitivity and maturation activity, while a Ni2+ concentration over 0.25 mg/L caused a significant decrease and produced even total blocking of the hormonal sensitivity and maturation ability of all oocytes, regardless of their initial hormonal sensitivity. The frog oocyte maturation test was shown to be a useful method to assess toxic effect of Ni2+ on water frog reproduction.

Apparent Competition by Grass Frogs (Rana temporaria) and Common Toads (Bufo bufo) for Breeding Sites

Apparent Competition by Grass Frogs (Rana temporaria) and Common Toads (Bufo bufo) for Breeding Sites