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Pool frog

The pool frog (Pelophylax lessonae) is a of in the family Ranidae, native to from and in the south to and in the north, where it inhabits stagnant or slow-flowing freshwater bodies such as ponds, lakes, marshes, and ditches typically surrounded by dense emergent vegetation. Adults measure 6–10 cm in snout-vent length, with males generally smaller than females, and exhibit a greenish-brown dorsum often marked with darker spots or ridges, while the venter is white with yellowish thighs. This species is notable for its role in a hybridogenetic reproductive complex with the (P. kl. esculentus), where P. lessonae transmits its genome clonally through hybrid offspring, maintaining distinct populations despite hybridization. Breeding occurs in and summer, with males producing loud, rattling calls from submerged positions to attract females, who lay clutches of 1,000–15,000 eggs in rafts attached to . Larvae develop in water over 1–3 months before metamorphosing, and adults are opportunistic predators feeding on like and small vertebrates, while hibernating in mud or leaf litter during winter. Although classified as Least Concern globally due to its wide distribution and stable populations in core ranges, the pool frog faces threats from habitat loss, fragmentation, and competition in peripheral areas, leading to local declines. In Britain, the northern clade of the pool frog became extinct by the mid-1990s due to drainage of wetlands and disease, but genetic studies confirmed its native status, prompting successful reintroductions since 2005 using Swedish stock to sites like Thompson Common in Norfolk, where populations have established and bred. These efforts, supported by habitat restoration, highlight conservation strategies for recovering marginal populations, though ongoing monitoring addresses risks from hybrids and environmental changes.

Taxonomy and Systematics

Etymology and Classification

The common name "pool frog" reflects the species' affinity for stagnant pools, , and other standing water bodies with dense vegetation. The scientific binomial Pelophylax lessonae was originally described as Rana lessonae by Italian herpetologist Lorenzo Camerano in 1882, based on specimens from . The genus name Pelophylax, established by Leopold Fitzinger in 1843, combines the Greek pēlos (mud) and phylax (sentinel or guard), evoking the frog's role in muddy ecosystems. In modern taxonomy, P. lessonae is classified within the family Ranidae (true frogs), reflecting shared morphological traits such as webbed toes, vomerine teeth, and a horizontal pupil. The full hierarchical classification is as follows:
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Amphibia
  • Order: Anura
  • Family: Ranidae
  • Genus: Pelophylax
  • Species: Pelophylax lessonae
This placement in Pelophylax resulted from phylogenetic revisions in the late 20th and early 21st centuries, which separated European water frogs from the broader Rana genus based on genetic, acoustic, and osteological evidence distinguishing them from Eurasian brown frogs.

Hybrid Complex Involvement

The pool frog (Pelophylax lessonae) serves as one parental species in the European water frog hybrid complex, alongside the marsh frog (P. ridibundus) and their hybrid, the edible frog (P. esculentus). This complex features hybridogenesis, a clonal reproductive mode in P. esculentus (genotype RL, where R denotes P. ridibundus and L denotes P. lessonae haplotypes), which transmits only the R genome to gametes while discarding the L genome during meiosis, necessitating mating with P. lessonae to regenerate the hybrid genotype. In typical mixed populations (L-E systems), P. lessonae persists through sexual reproduction, providing the essential L genome to sustain P. esculentus populations, though the hybrid often dominates numerically due to its reproductive efficiency. Hybridogenesis imposes fitness dependencies: P. esculentus survival and reproduction rely on co-occurrence with P. lessonae, as self-sustaining all-hybrid populations are unstable without occasional R genome input from P. ridibundus. Studies indicate higher adult survival rates in P. lessonae compared to P. esculentus in sympatric populations, with recapture probabilities elevated in males of both forms, suggesting ecological pressures favor the parental species under certain conditions. Mate choice further structures these systems; P. esculentus females preferentially select P. lessonae males over conspecifics, enhancing hybrid production but potentially diluting P. lessonae genetic integrity through asymmetric hybridization. Genomic analyses reveal recurrent hybridization origins, with P. esculentus arising multiple times from P. lessonae × P. ridibundus crosses, leading to diverse levels (diploid and triploid) and population structures across . Deleterious mutations accumulate in the clonally transmitted R genome of P. esculentus, contributing to hybrid load and long-term without P. lessonae replenishment, as evidenced by comparative fitness metrics in experimental and wild populations. Despite this, P. lessonae maintains viability in hybrid zones, with electrophoretic and karyotypic distinctions (e.g., C-band patterns) confirming its distinct parental role amid ongoing .

Physical Characteristics

Morphology and Variation

The pool frog (Pelophylax lessonae) has a chunky body form with a moderately sharp , webbed hind toes, and a large inner metatarsal ; when the shins are positioned perpendicular to the body axis, the heels fail to meet. Adult snout-vent length typically ranges from 4 to 8 cm, with females attaining larger sizes than males, up to approximately 8 cm. Dorsal coloration varies among green, yellowish-green, olive-green, or greyish-green hues, marked by dark spots differing in number, size, and distribution. A light middorsal line and lines along the dorsolateral folds are consistently present, with no temporal spot evident. The ventral surface is white or yellowish-white, generally unspotted, though flanks may appear more yellowish during the breeding season in both sexes. Geographic variation in external morphology includes differences in dorsal pigmentation; northern populations, such as those in and reintroduced stock, are predominantly brown with dark brown or black blotches, contrasting with the greener tones prevalent in central and southern specimens. Spot patterns and overall coloration show intraspecific variability, influenced by local environmental factors and , though the species maintains diagnostic traits distinguishing it from congeners like the .

Sexual Dimorphism

Adult female Pelophylax lessonae typically reach a snout-vent length of up to 7 cm, while males rarely exceed 6.5 cm, exhibiting female-biased size dimorphism common in many ranid frogs. Males possess paired white vocal sacs located behind the mouth angles, which inflate during calling in the breeding season to amplify advertisement calls. Additionally, breeding males develop dark gray nuptial pads on the thumbs (first finger) and display greater forelimb robustness, adaptations facilitating amplexus during mating. Females lack these structures. In northern European populations, sexual color dimorphism is pronounced, with males often dorsally and females nearly , contrasting with the more uniform to olive- dorsal coloration with dark spots observed across the ' range. During , flanks of both sexes become more yellowish, while the belly remains white or yellowish-white and typically spotless. No significant occurs in iliac bone length except slight differences favoring larger female dimensions, aligning with overall body size variation.

Distribution and Habitat

Geographic Range

The pool frog (Pelophylax lessonae, syn. Rana lessonae) is native to , with its range spanning from the westernmost localities in (e.g., and regions) and to the northwestern coast, , and (from Byelgorod to Provinces). The southern margin includes parts of the former , , and . Its distribution covers a broad swath of central and , including countries such as , , , , , , , , , , , , , , , , , , , , , , , , , , , , , and . Northern limits reach southern (near ), southern (along the ), , and northwestern (from Leningrad to Bashkiria regions). The species' extent of occurrence reflects adaptation to varied lowland habitats, though patchy distributions occur in northern metapopulations, such as isolated populations first documented in the 1940s. Outside its native range, P. lessonae has been introduced to and the ; in , native populations presumed extinct by the mid-1990s have undergone successful reintroductions from and stock since 2005. The IUCN assesses the species as Least Concern globally, citing its wide European distribution, though regional declines from habitat loss and hybridization affect some areas.

Habitat Requirements

The pool frog (Pelophylax lessonae) primarily inhabits stagnant or slow-flowing freshwater bodies such as , swamps, ditches, and large puddles, which are typically covered with dense herbaceous providing and breeding substrates. These sites must be permanent or semi-permanent to support larval development, with shallow, oligotrophic waters free of to minimize egg and mortality. requires water temperatures exceeding 16°C, typically from mid-May to mid-June in northern populations, to initiate spawning in sunny, warm-exposed areas. Terrestrially, pool frogs favor damp, densely vegetated landscapes including mosaics of early successional stages, shrublands, grasslands, and moist forest edges, where they forage and disperse. Adults and juveniles preferentially select wetter microhabitats with high topographic wetness, such as areas near or in low-relief terrain, avoiding dry coniferous forests like Scots stands that increase risk. occurs on land in at depths of 5–20 cm, typically within 250 m of breeding ponds, often in shaded, moist Norway spruce-dominated habitats rather than dense or open-canopy clearcuts. Habitat connectivity is essential, with movements—often nocturnal and rain-facilitated—following moist corridors like for dispersal up to several hundred meters, supporting dynamics in fragmented landscapes. efforts emphasize maintaining or creating multiple (at least six per site) adjacent to managed terrestrial habitats, with vegetation thinning to enhance and warmth while preserving gradients.

Status in Britain

The pool frog (Pelophylax lessonae) was historically native to eastern England, occurring in fenland and breckland habitats, but populations declined due to habitat drainage and agricultural intensification, leading to extinction in the wild by the early 20th century. Last confirmed records date to Norfolk in the 1920s, with the species presumed extinct in the wild by 1995. Initial debates questioned its native status versus classification as an introduced alien, but historical records, subfossil evidence, and genetic analyses confirmed it as indigenous to Britain. Reintroduction efforts began in 2005 under a developed by and the Amphibian and Reptile Conservation Trust, sourcing northern clade frogs from —genetically closest to historical lineages—to restore populations in , the species' last stronghold. Between 2005 and 2008, over 800 individuals were translocated to a prepared site in , establishing a self-sustaining breeding population by 2010. A second site at Thompson Common received head-started metamorphs from 2015 onward to enhance viability, with both populations now reproducing successfully without adverse impacts on native amphibians. The species is one of four amphibians protected under the UK's , with ongoing monitoring for disease risks like . As of 2017, the estimated population across the two sites totaled approximately 60 adults, though short-term trends (2007–2018) show increases. Under the Habitats Directive, the UK's remains unfavourable-bad due to limited distribution and numbers below favourable reference levels (target: 10,000 individuals), despite favourable habitat conditions and an improving overall trend. Populations continue to thrive as of 2022, with no natural spread beyond release sites reported.

Ecology and Behavior

Diet and Foraging

The pool frog (Pelophylax lessonae) is carnivorous across post-metamorphic life stages, with adults primarily consuming terrestrial , particularly . Studies in mixed populations indicate that comprise approximately 88% of the , with (e.g., , wasps) accounting for 28% and Coleoptera (beetles) for 18% of prey items by frequency. Aquatic , such as water striders () and diving beetles (), form less than a quarter of the , reflecting a preference for terrestrial despite semi-aquatic habitats. Juveniles target large quantities of flies and fly larvae, occasionally supplemented by other small arthropods. Tadpoles are herbivorous-detritivorous, feeding mainly on algae including Cyanophyta and , alongside tiny and decaying in pond substrates. This diet supports rapid growth in shallow, vegetated waters, with involving scraping and filtering from surfaces. employs an opportunistic sit-and-wait strategy, typical of ranid frogs, where individuals perch on vegetation or ground and strike at moving prey to trigger feeding responses. Adults and juveniles may climb low vegetation up to 0.5 meters to ambush aerial or arboreal , extending access beyond immediate edges. Feeding persists through the breeding season, though intensity is lower than in larger congeners like P. ridibunda due to P. lessonae's smaller body size and energy allocation to reproduction. Rare predation on conspecifics or juvenile grass snakes (Natrix natrix) occurs, but vertebrates are incidental in the diet.

Activity Patterns and Movement

The pool frog (Pelophylax lessonae) exhibits seasonal activity primarily , emerging from in or May when water temperatures exceed 10°C, with peak breeding activity in May and , and entering by late September or early October. occurs in terrestrial burrows or under vegetation near breeding sites, with both P. lessonae and its hybrid associate P. esculenta showing similar timing in natural habitats. Diel activity includes both diurnal and nocturnal phases, influenced by ; individuals prefer warmer conditions and shift toward activity as temperatures decline, often basking in shallow or on banks during daylight to thermoregulate. Foraging and general locomotion occur mainly during the day, though calling and some movements may extend into night, particularly during . Movement patterns involve both local foraging displacements and longer-distance dispersal, with adults and juveniles showing target-oriented behavior toward neighboring ponds or marshes rather than random wandering. Dispersal occurs year-round without seasonal restriction, though rates decline with increasing inter-pond distances; adults typically move 100–500 m between sites, while chains of small ponds enable migrations up to 8 km. Juveniles direct movements to adjacent P. lessonae localities, and males appear to disperse farther than females in some populations. Group migrations distinguish from individual dispersal, facilitating metapopulation connectivity in fragmented landscapes.

Predators and Parasites

The tadpoles of the pool frog (Pelophylax lessonae, syn. Rana lessonae) exhibit predator-induced morphological in response to predators such as ( spp.), which detect prey visually and via burst swimming, leading to deeper-bodied tadpoles with reduced tail depth for improved escape performance. In contrast, exposure to invertebrate predators like larvae prompts shallower bodies and longer tails suited to slow, sustained swimming against gape-limited predators. such as and newts also prey on tadpoles, eliciting anti-predator behaviors including reduced activity and shifts in both P. lessonae and its associate P. esculentus. These responses vary by predator complement, with predation disproportionately affecting P. lessonae tadpoles over hybrids in mixed populations. Adult pool frogs face predation from wetland predators including birds (e.g., herons), snakes, and mammals, though quantitative data specific to P. lessonae remain sparse; survival studies indicate higher annual recapture rates in males than females, potentially reflecting sex-specific predation risks. Non-lethal predator cues, such as those from caged fish, induce life-history shifts like accelerated growth and metamorphosis under time constraints, enhancing escape from seasonal predation windows. Parasites of P. lessonae include nematodes such as Icosiella neglecta, a filarial worm transmitted by mosquitoes and prevalent in Palearctic ranid frogs, often infecting and subcutaneous tissues. Other helminths, predominantly geohelminths from soil-transmitted genera (e.g., Rhabdias, Cosmocerca), form diverse communities in habitats, with prevalence varying by site and host density. Mesomycetozoean parasites like Amphibiocystidium ranae (formerly grouped under Dermocystidium ranae) cause dermal infections and have been linked to epizootics in populations, correlating with mass mortalities and contributing to declines alongside factors. In hybridogenic systems with P. esculenta, P. lessonae hosts experience lower lung nematode intensities than hybrids, potentially due to genetic factors like heterozygosity, though overall parasite burdens can influence hybrid fitness as "genetic parasites." Zoosporic parasites and paramphistomes add to the diversity, with genetic analyses revealing unexpected variability in frog-infecting trematodes.

Reproduction

Breeding Biology

Pool frogs (Pelophylax lessonae) exhibit seasonal breeding primarily in to early summer, with activity peaking from May to June in temperate regions such as , triggered by warming air and water temperatures above approximately 15–18°C. Males establish territories in shallow, vegetated margins and loud, repetitive advertisement calls at night to attract females, often developing a yellowish-green coloration during this period. Mating occurs via axillary , where males grasp females, stimulating oviposition; females deposit eggs in spherical or irregular clumps attached to submerged or debris in warm, still waters. These spawn masses are smaller than those of the (Rana temporaria), typically measuring 5–10 cm in diameter with eggs of reduced size (around 1–1.5 mm), and containing several hundred to approximately 1,000 eggs per clump depending on female condition. Clutch sizes vary, with field observations from reintroduction efforts recording averages of about 120 eggs per clump across multiple females. Eggs hatch within 4–5 days into tadpoles under optimal temperatures (18–25°C), which initially appear minute but undergo rapid growth, developing external gills and feeding on algae and detritus. Tadpole development spans 6–10 weeks, culminating in metamorphosis to froglets between late July and September in northern populations; late-hatching individuals may overwinter as tadpoles, emerging the following spring, and attain larger body sizes than common frog tadpoles. Breeding success depends on water quality, temperature stability, and absence of predators, with males exhibiting prominent whitish vocal sacs during chorusing.

Hybridogenesis Mechanism

In the hybridogenetic water frog complex, Pelophylax kl. esculentus (previously Rana esculenta), the diploid hybrid between the pool frog (P. lessonae, genotype LL) and the marsh frog (P. ridibunda, genotype RR; genotype LR), reproduces via hybridogenesis, a form of hemiclonal . During in the hybrid, the P. lessonae (L) is selectively eliminated prior to , preventing recombination between the two divergent parental . The retained P. ridibunda (R) then undergoes premeiotic endomitosis ( duplication), followed by standard meiotic division, resulting in haploid gametes that clonally transmit the unrecombined R . This process perpetuates the hybrid lineage in mixed L-E populations, where P. kl. esculentus coexists with P. lessonae. Hybrids preferentially mate with P. lessonae, providing L gametes that fertilize the clonal R gametes from hybrids, restoring the LR diploid in and ensuring hybrid persistence without producing viable LL or RR progeny from hybrid-hybrid matings. In such systems, P. lessonae acts as a sexual host, its incorporated only to reconstruct hybrids, while the R propagates clonally across generations, sometimes preserving extinct lineages. Intrapopulation variation occurs rarely, with some hybrids eliminating either , but L elimination predominates in L-E . Pure P. lessonae populations reproduce bisexually via standard , producing recombinant LL gametes, but hybridogenesis indirectly impacts their dynamics by imposing a parasitic load, as hybrids outcompete or displace P. lessonae in some regions through higher or . This maintains genetic uniformity in the transmitted R component while relying on P. lessonae for viability, differing from full clonality by incorporating host genetic input each generation.

Conservation

Population Trends and Status

The pool frog (Pelophylax lessonae) holds a global conservation status of Least Concern according to the IUCN Red List, reflecting a population that is widespread across central and northern Europe with no evidence of broad-scale decline. However, regional trends vary, with local extinctions and reductions attributed to habitat loss, pollution, and competitive displacement by hybrids in mixed water frog populations. In , studies indicate significant declines in the proportion of pure P. lessonae within hybridogenic systems over the last half-century. For example, in Polish landscapes, historical frequencies of P. lessonae exceeding 68% in rural sites and 89% in areas have plummeted to under 2% and 3%, respectively, likely due to asymmetric hybridization favoring the hybrid (P. kl. esculentus). Similar patterns of replacement by hybrids have been documented in other mixed populations, contributing to fragmentation. In , the pool frog became extinct in the wild during the mid-1990s, but post-reintroduction assessments under the EU report an improving population trend as of 2019, with stable range and habitat conditions supporting persistence at Norfolk reintroduction sites using northern European () stock. Monitoring confirms breeding success and recruitment at these locations, marking a reversal of historical loss without negative impacts on co-occurring species.

Primary Threats

The primary threats to Pelophylax lessonae populations across its range include and , primarily driven by of wetlands, for , and the disappearance of small oligotrophic ponds for . Agricultural intensification has further exacerbated this by altering hydrological regimes and reducing suitable shallow pool habitats, leading to local extinctions in fragmented landscapes. Disease poses a significant risk, particularly from pathogens such as (chytrid fungus) and ranavirus, which have been identified as high-threat factors in disease risk assessments for reintroductions and wild populations. These diseases can cause mass mortality events in amphibians, with pool frogs acting as potential hosts that facilitate spread to co-occurring species. Hybridization and competitive displacement by hybrid water frogs (Pelophylax esculentus) represent another key threat, as P. lessonae has declined sharply in mixed populations—from 89.1% to 2.7% in urban areas and 68% to 1.8% in rural areas in some regions—due to the hybridogenetic favoring hybrid persistence over pure lessonae genotypes. This process, combined with , limits and increases vulnerability in isolated metapopulations. and competition contribute additionally but are secondary to these core pressures in documented declines.

Management and Reintroduction Efforts

Management efforts for the pool frog (Pelophylax lessonae) emphasize habitat restoration and maintenance to support breeding in shallow, vegetated ponds, often involving to prevent to dense and the creation of temporary water bodies mimicking natural pingos. In , where the species is red-listed and populations number around 120 localities, practices have been adjusted based on movement studies showing frogs travel up to 500 meters from ponds, recommending buffer zones around breeding sites to minimize habitat disruption during logging. Reintroduction programs have focused on the United Kingdom, where the native northern clade population extinct by the 1990s, with a strategy outlined in 2005 by English Nature (now Natural England) selecting source stock from Sweden due to genetic similarity confirmed via mitochondrial DNA analysis. Initial releases began in 2005 at military training areas in Norfolk and Suffolk, followed by civilian sites; over 590 Swedish-sourced adults and head-started tadpoles were introduced through 2021 as part of the Pingo Project at Thompson Common, involving excavation of six new pingos and restoration of eight existing ones alongside grassland enhancement. Head-starting trials, rearing tadpoles in captivity before release, have improved survival rates, with protocols including disease screening for ranavirus and Batrachochytrium dendrobatidis to mitigate risks. Post-release via call surveys, traps, and genetic verification has documented success and population establishment at reintroduction sites by 2021, though ongoing efforts target additional populations to ensure viability. In , reintroductions are rarer, but habitat connectivity projects under EU LIFE initiatives in have indirectly benefited pool frogs by restoring networks in cultural landscapes.

References

  1. [1]
    Pelophylax lessonae - AmphibiaWeb
    The species lives in Europe. The westernmost localities are in France (Garonne, Grenoble etc.) and Southern Italy.Missing: Rana | Show results with:Rana
  2. [2]
    Population structure, mate choice, and genome transmission in ...
    Jul 26, 2023 · An analysis of genome transmission to gametes revealed that females P. lessonae transmitted Lx, while P. esculentus transmitted the Rx and/or Lx ...
  3. [3]
    Hibernation behavior of Rana lessonae and R. esculenta in their ...
    We studied the hibernation behavior of the water frog Rana lessonae and its hybridogenetic associate R. esculenta in their natural habitat during three ...Missing: taxonomy | Show results with:taxonomy
  4. [4]
    Pool frog - Rana lessonae - Camerano, 1882 - EUNIS
    The species is viable and maintaining itself on a long-term basis, its natural range is not reduced, and it has a sufficient large habitat.
  5. [5]
    Historic reintroduction reverses extinction of England's rarest frog
    Jul 28, 2021 · The northern pool frog, England's rarest amphibian, has been successfully reintroduced to Thompson Common, in Norfolk – reversing its disappearance from there ...
  6. [6]
    Northern Pool Frog Recovery - Amphibian and Reptile Conservation
    Sep 28, 2022 · The northern pool frog became extinct from England in the 1990s, but since then (from 2005-2008) it has been reintroduced using closely related frogs from ...Missing: Britain | Show results with:Britain
  7. [7]
    [PDF] UK conservation status assessment for S6981 - Pool frog ... - JNCC
    Overall trend in Conservation Status is based on the combination of the short- term trends for Range – stable, Population – improving, and Habitat for the.Missing: biology | Show results with:biology
  8. [8]
    Pelophylax lessonae (Camerano, 1882)
    Polon., 39: 160, as an unavailable name published as a synonym of Rana esculenta. The name actually reported by Linnaeus is non-binomial, Rana viridis aquatica ...Missing: etymology | Show results with:etymology
  9. [9]
    Pelophylax - an overview | ScienceDirect Topics
    Pelophylax composed of pēlos Greek, mud and phulax Greek, sentinel; saharicus Latinized from the Arabic for desert (sahrā'), of the desert, Saharan; riodeoroi ...Missing: origin | Show results with:origin
  10. [10]
    Pelophylax lessonae (Pool frog) | Taxonomy - UniProt
    Mnemonic name. PELLE · Taxon ID. 45623 · Scientific name. Pelophylax lessonae · Parent. Pelophylax · Common name. Pool frog · Synonyms. Rana lessonae · Other names.Missing: classification | Show results with:classification
  11. [11]
    Pelophylax lessonae - NCBI - NLM
    Pool frog (Pelophylax lessonae) is a species in the family Ranidae (riparian frogs).
  12. [12]
    Population genomics of an exceptional hybridogenetic system of ...
    Aug 5, 2019 · A microsatellite-based method for genotyping diploid and triploid water frogs of the Rana esculenta hybrid complex. Mol Ecol Notes. 2005;5 ...
  13. [13]
    HYBRID POPULATIONS OF <i>RANA ESCULENTA</i> WATER ...
    Rana esculenta, the common edible frog of Europe, arose and recurrently arises by hybridization between R. lessonae. (genotype LL) and R. ridibunda (genotype RR) ...<|separator|>
  14. [14]
    Survival in adults of the water frog Rana lessonae and its ...
    Survival rates were consistently higher in R. lessonae than in R. esculenta. Recapture probability was higher in males than in females. In both species, ...
  15. [15]
    Male vocalization and female choice in the hybridogenetic Rana ...
    Hibernating behavior of Rana lessonae and R. esculenta in their natural habitat in Switzerland. Oecologia, 123 (2000), pp. 41-47. View in Scopus Google ...
  16. [16]
    mate choice in mixed populations of sexual and hybridogenetic ...
    Mate choice and fitness in a hybrid frog: Rana esculenta females prefer Rana lessonae males over their own. ... Rana lessonae/Rana esculenta complex. Anim ...
  17. [17]
    The role of deleterious mutations in the stability of hybridogenetic ...
    May 16, 2014 · In this paper we consider the two species Pelophylax ridibundus and Pelophylax lessonae, and their hybrids Pelophylax esculentus. P. lessonae ...
  18. [18]
    Reproduction and hybrid load in all-hybrid populations of Rana ...
    All-hybrid populations of the water frog, Rana esculenta, are exceptional in consisting of independently and to some extent sexually reproducing interspecific ...
  19. [19]
    Hybridogenesis in Rana esculenta: C‐band karyotypes of Rana ...
    C-banding patterns have been studied in R. ridibunda, R. lessonae and R. esculenta from Austrian waterfrog populations of R. lessonae+R. esculenta, ...
  20. [20]
    Electrophoretic Phenotypes of Rana ridibunda, Rana lessonae, and ...
    The data indicate a large degree of genetic difference between the two parental species, supporting prior observations on serum albumin, morphology, and ecology ...
  21. [21]
    Pelophylax lessonae | Overview | Finnish Biodiversity Info Facility
    Description. The pool frog is smaller and shorter than the lake frog and the edible frog. Adult individuals reach a length of 4-7 cm, rarely 8 cm (SVL).
  22. [22]
    [PDF] The ecology and evolution of the northern pool frog (Pelophylax ...
    Sep 27, 2024 · Summary: Pool frogs (Pelophylax lessonae) in northern Europe provide an intriguing opportunity to study a species complex in a conservation ...
  23. [23]
    Northern pool frog - Amphibian and Reptile Conservation
    Jul 2, 2016 · The pool frog has full protection under UK law, including The Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species ...
  24. [24]
    Pool Frog (Amphibians of Serbia - guide) · iNaturalist
    It is usually olive-brown above, with dark-brown blotches, and a prominent yellow line running down the centre of the back. Pool frogs from central and southern ...Missing: color | Show results with:color
  25. [25]
    https://brill.com/view/journals/amre/13/3/article-p235_4.xml
  26. [26]
    Pelophylax lessonae - Lessona's Frog - HerpetoSavona
    Fact sheet on Lessona's Frog (Pelophylax lessonae) ... Description. Lessona's Frog ( Pelophylax lessonae Pelophylax lessonae ) ... Sexual dimorphism is also seen in ...
  27. [27]
    [PDF] Pool frog (Pelophylax lessonae) CAMERANO 1882 (Anura, Ranidae ...
    The frogs show the external characteristics of the northern clade of the species, which suggests that they are of different origin than the allochthonous edible ...
  28. [28]
    Variation in the ilium of central European water frogs Pelophylax ...
    Jan 8, 2015 · A total of 454 ilia of modern green frogs from the former German Democratic Republic have been studied: 168 for P. lessonae (86 of males and 82 ...Missing: color | Show results with:color
  29. [29]
    [PDF] OBSERVATIONS ON THE POOL FROG, RANA LESSONAE ...
    Jul 16, 2020 · The occurrence of R. lessonae in Southern Norway near Arendal (Aust Agder country) has recently been documented (Dolman, 1996).<|separator|>
  30. [30]
    [PDF] (RANA LESSONAE) POPULATIONS
    The isolated Swedish metapopulation of pool frogs (Rana lessonae) was not discovered until the I 940s and is classified as "vulnerable" in conservation ...Missing: color | Show results with:color
  31. [31]
    [PDF] Global Re introduction_Cover_2018 Cover_1
    The pool frog (Pelophylax lessonae) is found through much of central and northern continental Europe. Its global IUCN Red List category is Least Concern.Missing: distribution | Show results with:distribution
  32. [32]
    (PDF) Movement and habitat use of the pool frog (Pelophylax ...
    Tree frog prefers a mosaic of habitats in landscapes including habitats of early successional stages and is also associated with shrublands and grasslands, and ...
  33. [33]
    [PDF] Pool Frog Species Action Plan - Amphibian Ark
    This document outlines the actions required to conserve the pool frog (Pelophylax (Rana) lessonae) in Britain and provides a framework for all conservation ...
  34. [34]
    Bringing back the pool frog to Britain | ZSL
    The pool frog is currently extinct in Britain.​​ Historically, the pool frog was present in Britain, but following loss and damage to their Fenland and Breckland ...Missing: Rana | Show results with:Rana
  35. [35]
    Neglected native or undesirable alien? Resolution of a conservation ...
    A recent UK conservation dilemma has centred on the status of the pool frog Rana lessonae. This species has been the subject of documented introductions ...
  36. [36]
    Reintroduction Strategy for the Pool Frog Rana lessonae in England
    A recent UK conservation dilemma has centred on the status of the pool frog Rana lessonae. This species has been the subject of documented introductions ...
  37. [37]
    Lost And Found: The Recovery Of England's Forgotten Frog - Forbes
    Sep 25, 2022 · Currently, the pool frog is one of only four amphibian species recognized by the UK government as protected under its Biodiversity Action Plan ( ...
  38. [38]
    Northern pool frogs return to the UK | Amphibians - The Guardian
    Apr 6, 2022 · Loud-croaking striped frogs, which had been extinct in Britain, are thriving after being reintroduced.
  39. [39]
    (PDF) Food habits of a Pool frog Pelophylax lessonae - ResearchGate
    Aug 7, 2025 · The results of our study reveal that there are no significant differences in the feeding habits of the two green frogs, Pelophylax lessonae and ...
  40. [40]
    Pool frog guide: species facts, how to identify, and when they were ...
    Are northern pool frogs endangered? Northern pool frogs occur as small populations, and have a very restricted distribution within the five northern European ...
  41. [41]
    Environmental DNA (eDNA) detects the pool frog (Pelophylax ... - NIH
    Apr 3, 2018 · The activity of P. lessonae during the spawning period is highly dependent on the water temperature. Reproduction does not start before the ...
  42. [42]
    Hibernation behavior of Rana lessonae and R. esculenta in ... - ZORA
    Jan 1, 2000 · We studied the hibernation behavior of the water frog Rana lessonae and its hybridogenetic associate R. esculenta in their natural habitat ...<|separator|>
  43. [43]
    Thermal Influences on the Habitat Preference and the Diurnal ...
    Three species with different habitat preferences during their summer ... Rana lessonae CAMERANO and Rana ridibunda PALLAS. The activity, the location ...
  44. [44]
    Pool Frog - Froglife
    Pool Frog (Pelophylax lessonae) · Identification, Adult females up to 9 cm in length. Males significantly smaller. · Distribution, Native to the UK. Very rare in ...
  45. [45]
    Spatial movement patterns in frogs: Target-oriented dispersal in the ...
    Abstract. The spatial movement pattern of pool frogs (Rana lessonae Camerano) was studied at two breeding ponds surrounded by drift fences at 60˚n in Sweden.
  46. [46]
    Spatial movement patterns in frogs: Differences between three Rana ...
    The temporal immigration and emigration patterns of the pool frog (. Rana lessonae), the moor frog (R. arvalis ) and the common frog (R. tem- poraria) at pond 1 ...
  47. [47]
    Dispersal rates and distances in adult water frogs, Rana lessonae, R ...
    Aug 8, 2025 · Dispersal occurred throughout the year and was not restricted to specific periods. The dispersal rate decreased with increasing pond-to-pond ...
  48. [48]
    Target-oriented dispersal in the pool frog, Rana lessonae1
    Deviations between captures of pool frogs (Rana lessonae) during days with group movements (migration) and individual move- ments (dispersal), respectively ...
  49. [49]
    Predator‐specific changes in the morphology and swimming ...
    May 24, 2005 · In this study, we examined the morphological responses of larval European Green Frogs (Rana lessonae) to both predatory sunfish (Lepomis ...
  50. [50]
    Effects of visual, chemical and tactile cues of fish on the behavioural ...
    The anti-predator behaviour of two closely related species of tadpoles, Rana lessonae ... Newts and trout are potential tadpole predators, but they find ...
  51. [51]
    Effects of predation risk and hunger on the behaviour of two species ...
    We examined the behavioural responses of two closely-related species of tadpoles, Rana lessonae and R. esculenta, to simulated predation by fish and hunger.Missing: diet | Show results with:diet
  52. [52]
    Predator complement determines the relative success of tadpoles of ...
    ... predation,. Rana ... lessonae relatively more vulnerable to fish predators and would increase the relative ... population of Rana lessonae and Rana esculenta.
  53. [53]
    PREDATOR‐INDUCED LIFE‐HISTORY PLASTICITY UNDER TIME ...
    Sep 1, 2002 · I investigated how time constraints affect the growth strategies of pool frogs (Rana lessonae) in the presence and absence of caged (ie, nonlethal) predators.
  54. [54]
    Blood parasites of water frogs (Pelophylax esculentus complex) from ...
    Icosiella neglecta is among the parasites that are common and widespread in Palearctic frogs of the family Ranidae including several taxa of water frogs.
  55. [55]
    (PDF) Parasitic nematodes of Pool Frog (Pelophylax lessonae) in ...
    Aug 9, 2025 · Conclusions. Nematodes of pool frog, excluding I. neglecta, belong to the group of soil-transmitted helminthes (geohelminth) and parasitize in ...
  56. [56]
    Ecological Analysis and Biodiversity of the Helminth ... - MDPI
    This work presents an ecological analysis of the community and biodiversity of helminths of the Pool Frog Pelophylax lessonae (Camerano, 1882) from floodplain ...
  57. [57]
    [PDF] Parasitic nematodes of Pool Frog (Pelophylax lessonae) in the ...
    Aug 29, 2019 · Is a widely specific parasite of amphibians. Definitive hosts: different species of amphibians of the genera Pelophylax, Rana, Bufo, Pelobates, ...
  58. [58]
    (PDF) Parasitism by Dermocystidium ranae in a population of Rana ...
    Aug 5, 2025 · ... predators, chemical pollu-. tion and climate change (Halliday 2001 ... Rana lessonae and their hybridogenetic associ-. ate Rana esculenta ...
  59. [59]
    https://www.researchgate.net/publication/258832003_Impacts_of_mesomycetozoean_parasites_on_amphibian_and_freshwater_fish_populations
  60. [60]
    (PDF) Heterozygosity and parasite intensity: Lung parasites in the ...
    ... Rana lessonae-esculenta complex in eastern France. In these mixed populations, hybrid frogs (R. esculenta) outnumbered parental ones (R. lessonae). Despite ...<|control11|><|separator|>
  61. [61]
    (PDF) zoosporic parasites of amphibians - ResearchGate
    Jan 21, 2016 · ... Rana lessonae, have. been attributed, at least in part, to an outbreak of the mesomycetozoean parasite. Amphibiocystidium ranae (Di Rosa et ...
  62. [62]
    novel molecular data reveal unexpected genetic diversity among ...
    The distribution and diversity of paramphistome parasites of frogs were investigated to some degree in the past; however, little is known about their genetic ...
  63. [63]
    Traditional monitoring - Bio-protocol
    The activity of P. lessonae during the spawning period is highly dependent on the water temperature. Reproduction does not start before the water has reached a ...Missing: breeding | Show results with:breeding
  64. [64]
    Rana lessonae Camerano 1862
    Dec 20, 1995 · Rana lessonae from Switzerland. Photograph copyright 1995, Hansjürg Hotz. About this page. Peter Beerli. e-mail: beerli@scs.fsu.edu ...
  65. [65]
    Frog - Pool - Let's Go Wild
    Oct 28, 2017 · Breeding coincides with the onset of warm nights in May/June. The spawn 'rafts' are typically smaller than those of the common frog, and ...
  66. [66]
    Pool Frog -Rana lessonae - Herpetofauna
    Very occasionally some green can be seen around the head. Distinguishable from other water frogs by relatively small size.Missing: variation | Show results with:variation
  67. [67]
    [PDF] A head-starting trial for the reintroduction of the pool frog Pelophylax ...
    The specific habitat requirements of the northern pool ... Genetic variation in relation to demography of peripheral pool frog populations (Rana lessonae).
  68. [68]
    An extinct vertebrate preserved by its living hybridogenetic descendant
    Oct 6, 2017 · Hybridogenesis is a special mode of hybrid reproduction where one parental genome is eliminated and the other is transmitted clonally.
  69. [69]
    Hybridogenesis in the Water Frogs from Western Russian Territory
    Feb 8, 2021 · Hybridogenesis in an interspecific hybrid frog is a coupling mechanism in the gametogenic cell line that eliminates the genome of one parental species.
  70. [70]
    Decline of Pelophylax lessonae in mixed populations of water frogs ...
    P. lessonae's frequency decreased from 89.1% to 2.7% in urban and 68% to 1.8% in rural areas, with habitat loss and fragmentation as key factors.
  71. [71]
    Extinction and isolation gradients in metapopulations: the case of ...
    Loral extinction along the intrinsic isolation gradient within metapopulations is reviewed with particular reference to a study of the pool frog (Rana lessonaé) ...Missing: decline | Show results with:decline
  72. [72]
    Conservation status and threats to the pool frog (Pelophylax ...
    Aug 9, 2025 · Especially the drying-up of bogs and the loss of small oligotrophic ponds had negative impacts on the development of P. lessonae populations. In ...
  73. [73]
    Environmental DNA (eDNA) detects the pool frog (Pelophylax ...
    Apr 3, 2018 · Here, we compared results from a newly developed eDNA approach and the traditional observational method for the endangered pool frog (Pelophylax ...
  74. [74]
    Disease Risk Analysis and Post-Release Health Surveillance for a ...
    Jul 8, 2016 · Ranavirus and Batrachochytrium dendrobatidis were considered high-risk disease threats for pool frogs at the destination site. Quarantine was ...Missing: primary | Show results with:primary
  75. [75]
    Pelophylax lessonae - Global Invasive Species Database
    Pool frogs Pelophylax lessonae, have been found to be hosts of the Chytrid fungus, Batrachochytrium dendrobatidis and co-occuring native amphibians have also ...
  76. [76]
    the case of native and invasive Pelophylax waterfrogs - PMC
    ... Rana lessonae and Rana esculenta. Copeia. 2004;3:638–646. [Google Scholar] ... Habitat isolation and habitat quality: consequences for populations of ...
  77. [77]
    Pingo Project and Pool Frog Reintroduction - Breaking New Ground
    The Pingo Project aimed to reintroduce Pool Frogs by restoring pingos, releasing 590 frogs from Sweden, and creating a self-sustaining population.
  78. [78]
    Reintroduction strategy for the pool frog in England - ENRR642
    Aug 16, 2005 · This report has been produced to guide the reintroduction of the northern clade pool frog _Rana lessonae_ in England.Missing: management | Show results with:management
  79. [79]
    LIFE 3.0 - LIFE08 NAT/D/000005
    Habitat management interventions were planned in 15 locations, all of which are secured for nature conservation purposes, either as natural reserves or through ...