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Western clawed frog
Western clawed frog
Western clawed frog
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Western clawed frog
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Pipidae
Genus: Xenopus
Species:
X. tropicalis
Binomial name
Xenopus tropicalis
(Gray, 1864)
Synonyms
  • Silurana tropicalis
    Gray, 1864

The western clawed frog (Xenopus tropicalis) is a species of frog in the family Pipidae, also known as tropical clawed frog.[2] It is the only species in the genus Xenopus to have a diploid genome.[3][4] Its genome has been sequenced,[5][6] making it a significant model organism for genetics that complements the related species Xenopus laevis (the African clawed frog),[7] a widely used vertebrate model for developmental biology. X. tropicalis also has a number of advantages over X. laevis in research, such as a much shorter generation time (<5 months), smaller size (4–6 cm (1.6–2.4 in) body length), and a larger number of eggs per spawn.[8]

It is found in Benin, Burkina Faso, Cameroon, Ivory Coast, Equatorial Guinea, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Nigeria, Senegal, Sierra Leone, Togo, and possibly Mali. Its natural habitats are subtropical or tropical moist lowland forests, moist savanna, rivers, intermittent rivers, swamps, freshwater lakes, intermittent freshwater lakes, freshwater marshes, intermittent freshwater marshes, rural gardens, heavily degraded former forests, water storage areas, ponds, aquaculture ponds, and canals and ditches.

Description

[edit]

The western clawed frog is a medium-sized species with a somewhat flattened body and a snout-vent length of 28 to 55 mm (1.1 to 2.2 in), females being larger than males. The eyes are bulging and situated high on the head and there is a short tentacle just below each eye. A row of unpigmented dermal tubercles runs along the flank from just behind the eye, and are thought to represent a lateral line organ. The limbs are short and plump, and the fully webbed feet have horny claws. The skin is finely granular. The dorsal surface varies from pale to dark brown and has small grey and black spots. The ventral surface is dull white or yellowish with some dark mottling.[9]

Distribution and habitat

[edit]

The western clawed frog is an aquatic species and is found in the West African rainforest belt with a range stretching from Senegal to Cameroon and eastern Zaire. It is generally considered a forest-dwelling species and inhabits slow-moving streams, but it is also found in pools and temporary ponds in the northern Guinea and Sudan savannas.[9]

Biology

[edit]

In the dry season, this frog lives in shallow streams and hides under tree roots, under flat stones, or in holes in the riverbank. It feeds primarily on earthworms, insect larvae and tadpoles. When the rainy season starts it migrates across the forest floor at night to find temporary pools. Spawning may take place in large pools with much vegetation, but tadpoles are also sometimes found in muddy pools with no vegetation. Single eggs may be attached to plants or they may float. The tadpoles have broad mouths and no jaws, but have long tentacles on their upper lips. The ventral fins of their tails are broader than the dorsal ones. Their body colour is generally orange and the tail transparent but in darker locations the tail may be blackish. The tadpoles feed by filtering zooplankton from the water. In large water bodies, they may form dense swarms. Metamorphosis takes place when the tadpoles measure about 5 cm (2 in) in length.[9]

Sex determination

[edit]

Sex determination in the vast majority of amphibians is controlled by homomorphic (morphologically indistinguishable) sex chromosomes.[10] As a result of this difficulty in sex chromosome identification, only a relatively small proportion of anuran species that have been karyotyped have also had their sex chromosomes identified.[11] Of the species in the genus Xenopus, all have homomorphic sex chromosomes.[11] Additionally, the DM-W gene on the W chromosome in some Xenopus species is the only sex-determining gene that has been identified in amphibians.[11] This DM-W gene was first identified in X. laevis, however it is not found in X. tropicalis.[11] Experimentation involving sex-reversed individuals, gynogenesis, triploids, and conventional crosses, has determined that X. tropicalis has three sex chromosomes: Y, W, and Z.[11] These three sex chromosomes produce three different male genotypes, YW, YZ, and ZZ (all are phenotypically identical) and two different female genotypes, ZW, and WW (all are phenotypically identical).[11] As a result, offspring of X. tropicalis can have sex ratios that differ from the commonly known 1:1 usually found in species with only two different sex chromosomes. For example, offspring resulting from a ZW female and a YZ male will have a sex ratio of 1:3 females to males and offspring resulting from a WW female and a ZZ male will be all female.[11] As a result of this sex determination system, both male and female X. tropicalis can be either heterogametic or homogametic which is extremely rare in nature.[11] The exact genetic mechanism and the exact alleles underlying this system is not yet known.[12] One possible explanation is that the W chromosome contains a female-determining allele that has function that is not found on the Z chromosome while the Y chromosome contains an allele that acts a negative regulator that is dominant over the female-determining allele on the W chromosome.[12]

Although X. tropicalis does have these three sex chromosomes, the frequency of these three sex chromosomes is not evenly distributed among this species' populations throughout its natural range. The Y chromosome has been identified from two localities in Ghana and in a laboratory strain that originated in Nigeria and the Z chromosome has been confirmed to exist in individuals from western and eastern Ghana.[12] Additionally, all three sex chromosomes have been found to exist together in X. tropicalis populations in Ghana and potentially elsewhere in its range as well.[12] Additionally, having irregular sex ratios in offspring is generally thought to be disadvantageous so whether or not the existence of three sex chromosomes in X. tropicalis is evolutionarily stable or an indication that the species is going through a sex chromosome transition (turnover), is still a question.[12] It seems likely that the emergence of the Y chromosome is the most recent event in the evolution of this species' sex chromosomes.[12] It is possible that in the future extinction of the Z chromosome would make it so that the W chromosome transitions into a X chromosome making this species with sex determined by an XY system.[12] It is also possible that if the Y chromosome were to go extinct, this species will have reverted to using an ancestral ZW system.[12]

Status

[edit]

The IUCN lists the western clawed frog as "Least Concern" because it has a wide distribution and is an adaptable species living in a range of habitats, and the population trend seems to be steady.[1]

Use as a genetic model system

[edit]
See also Xenopus#Model organism for biological research

Xenopus embryos and eggs are a popular model system for a wide range of biomedical research.[3][13] This animal is widely used because of its powerful combination of experimental tractability and close evolutionary relationship with humans, at least compared to many model organisms.[13]

Unlike its sister species X. laevis, X. tropicalis is diploid and has a short generation time, facilitating genetic studies.[3] The complete genome of X. tropicalis has been sequenced.[5] This species has n=10 chromosomes.[14]

X. tropicalis has three transferrin genes, all of which are close orthologs of other vertebrates. They are relatively far from non-vertebrate chordates, and widely divergent from protostome orthologs.[15]

Online Model Organism Database

[edit]

Xenbase[16] is the Model Organism Database (MOD) for both Xenopus laevis and Xenopus tropicalis.[17]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Western clawed frog

View on Grokipedia
from Grokipedia
The Western clawed frog (Xenopus tropicalis), also known as the tropical clawed frog, is a small, fully aquatic in the family Pipidae, characterized by its flattened body, webbed feet with four horny claws, and a diploid that makes it a valuable in and . Native to the rainforests, gallery forests, and humid savannas of —from in the north to in the south—this nocturnal frog inhabits still or slow-running waters such as ponds, pools, and brooks, where it spends its entire life cycle submerged. Physically, X. tropicalis measures 28–55 mm in snout-vent length (SVL), with males averaging 36 mm and females 50 mm; it features a light to dark brown dorsal surface with spots, a whitish to yellowish ventral side with black mottling, small protruding eyes, and a below each eye. Its diet consists primarily of arthropods, larvae, and tadpoles, which it captures using its clawed feet, while its tadpoles have broad mouths and metamorphose at a total length under 5 cm. Reproduction occurs via inguinal , with spawning typically in July–August during the rainy season, when eggs are attached to aquatic vegetation; the species has a short generation time of about 6 months, producing thousands of embryos per clutch, which facilitates large-scale experimental studies. In research, X. tropicalis offers advantages over its relative Xenopus laevis due to its simpler diploid (approximately 1.7 billion base pairs across 10 pairs), faster maturation, and compatibility with genetic tools like screens and transgenics, enabling investigations into developmental , environmental , and human models. The species' was the first to be fully sequenced in 2010, enhancing efforts. Although historically used in pregnancy tests, X. tropicalis is classified as Least Concern by the (2019), with no major threats identified, though habitat degradation in its range warrants monitoring.

Taxonomy

Classification

The western clawed frog bears the binomial name Xenopus tropicalis Gray, 1864, originally described in a publication introducing the new genus Silurana for this species from . This name places it within the genus Wagler, 1827, part of the family Pipidae Gray, 1825, which comprises fully aquatic, tongueless frogs adapted to permanent water bodies. The species is classified under the order Anura, the frogs. A recognized synonym is Silurana tropicalis (Gray, 1864), reflecting historical taxonomic placements that sometimes separated it into the subgenus or genus Silurana based on morphological distinctions, though current consensus retains it within . Recent phylogenetic studies, such as Evans et al. (2015), have expanded the recognized diversity in the genus by describing six new species and revalidating others. Early classifications occasionally linked it to the genus Hymenochirus due to similarities in size and aquatic habits, but phylogenetic analyses have clarified its distinct position. The type locality is "West Africa, Lagos" (now in Nigeria), based on syntypes consisting of metamorphs and tadpoles collected around 1858. X. tropicalis is notable for its diploid karyotype with 2n=20 chromosomes, serving as a genetic model that contrasts with the allotetraploid Xenopus laevis (2n=36). This ploidy difference underscores its utility in comparative genomic studies within the genus.

Phylogenetic relationships

The Western clawed frog, Xenopus tropicalis, is classified within the subgenus Silurana of the Xenopus, a lineage characterized by pseudotetraploidy in some members, distinguishing it from the allotetraploid Xenopus subgenus. The Xenopus includes 29 , with X. tropicalis belonging to a West African that diverged early in the genus's evolutionary history. Molecular phylogenetic analyses, based on and nuclear markers, position X. tropicalis as the sister to the tetraploid Xenopus epitropicalis, forming a monophyletic group within Silurana. Estimates from molecular clocks indicate that the lineage leading to X. tropicalis diverged from that of around 48 million years ago, reflecting significant evolutionary separation within the Pipidae family. This divergence is supported by comparative genomic studies highlighting distinct levels and genetic architectures between the diploid X. tropicalis and the allotetraploid X. laevis. The genome of X. tropicalis was sequenced in 2010, yielding a draft assembly of approximately 1.5 gigabases containing over 20,000 protein-coding genes. This sequencing effort revealed extensive synteny with the human genome, particularly in large chromosomal regions, facilitating its use in comparative evolutionary and developmental studies across vertebrates. Although interspecific hybridization between X. tropicalis and other Xenopus species, such as X. laevis, can occur experimentally to produce hybrid embryos, natural reproductive isolation is maintained primarily due to ploidy differences—diploidy in X. tropicalis versus tetraploidy in many congeners—leading to inviable or sterile offspring.

Description

Morphology

The Western clawed frog (Xenopus tropicalis) exhibits a dorsoventrally flattened, streamlined body adapted for an exclusively aquatic lifestyle, with an oblong to ovoid shape in dorsal view that facilitates efficient . Adults typically attain a snout-vent (SVL) of 28–55 mm, with males averaging 36 mm and females 50 mm, and an average body mass of approximately 5–11 g depending on sex and condition. The head is subtriangular, featuring a blunt rostrum that projects slightly beyond the lower and small, protruding eyes positioned dorsally for unobstructed vision while submerged; these eyes lack movable eyelids and are encircled by a ring of skin bearing lateral-line plaques. A short , measuring 0.3–0.5 times the eye , extends below each eye, aiding in sensory perception. The lateral-line system, consisting of double rows of 15–20 sensory tubercles along the flanks, enables detection of movements and changes for and prey . The forelimbs are moderately robust and unwebbed, with elongate digits ending in bulbous tips and a single dark, keratinous on the enlarged prepollex for grasping and anchoring. In contrast, the hind limbs are shorter relative to body size but powerful, with fully webbed feet that enhance propulsion; these include three clawed toes on the first, second, and third digits, plus a fourth formed by the enlarged inner metatarsal , all used for anchoring to substrates. The skin is smooth to finely granular, glandular, and coated in protective that reduces drag and prevents , with scattered small spicules on the dorsum and tubercles on the plantar surfaces. Lacking a , X. tropicalis employs a suction-feeding mechanism, drawing prey into the via rapid buccal expansion, aided by small monocuspid teeth restricted to the upper (premaxilla) for grasping. Internally, adults rely on well-developed lungs for primary respiration, supplemented by cutaneous through the highly vascularized skin, while tadpoles utilize that are resorbed during ; this retention of aquatic traits reflects neotenic adaptations to a fully aquatic existence.

Size and coloration

The western clawed frog (Xenopus tropicalis) exhibits in adult body size, with females typically larger than males. Adult females reach a snout-vent length (SVL) of 48–55 mm (mean 50 mm), while males measure 32–39 mm SVL (mean 36 mm). Tadpoles attain a total length of 23–46 mm at the onset of , after which the SVL measures 11.5–15.5 mm upon completion. Post- growth is rapid, enabling juveniles to reach within 4–6 months, though females may take slightly longer at around 7 months. In captivity, individuals can reach up to 16 years. The dorsal surface displays a pale to dark brown or olive coloration, often accented by numerous fine black spots that do not coalesce into larger patterns. The ventral side is dull white to yellowish, sometimes with vague dark mottling. During the breeding season, males develop darkened nuptial pads on the inner surfaces of their forelimbs. Coloration shows geographic variation, with individuals from forested habitats tending toward darker dorsal tones compared to those in open areas. Outside of breeding, there is no pronounced sexual dichromatism.

Distribution and habitat

Geographic range

The Western clawed frog (Xenopus tropicalis) is native to the forested regions of , extending from eastward to and possibly further south to . This distribution encompasses countries including , , , , , , Côte d'Ivoire, , , , , and , primarily within the equatorial belt between approximately 5°N and 10°N . Some older records suggest a broader range including , the , and , though recent genetic studies limit it to up to the Sanaga River in . The species occupies lowlands up to about 400 m elevation and is absent from the arid due to unsuitable dry conditions. Introduced populations have been documented outside its native range, notably a breeding population detected in Riverview, Hillsborough County, Florida, USA, in 2021, initially misidentified as Xenopus laevis. This establishment likely resulted from escapes or releases from nearby research facilities at the . As of 2025, no other established wild populations are known beyond , though the Florida occurrence raises concerns about potential invasiveness in subtropical wetlands. The species was first described in 1864 by based on specimens from the type locality in , (then part of ). Its native range has shown relative stability over time despite ongoing habitat degradation from , with populations persisting in suitable aquatic habitats; however, increased monitoring is recommended to assess potential impacts from international trade in research specimens.

Habitat preferences

The Western clawed frog (Xenopus tropicalis) inhabits slow-moving or still freshwater environments, including streams, ponds, swamps, shallow brooks, and muddy pools, primarily within regions and gallery forests of . These microhabitats provide suitable conditions for its fully aquatic lifestyle, with individuals frequently floating at the water surface and retreating into dense vegetation when disturbed. The species exhibits broad tolerances in , thriving in both clear and , whether vegetated or not, and can endure stagnant conditions with low oxygen levels. It avoids fast-flowing rivers, preferring depths typically ranging from 0.5 to 2 meters in permanent or semi-permanent bodies, where muddy substrates and aquatic offer cover and foraging opportunities. Water parameters in its natural range reflect the tropical climate of its distribution. Seasonally, X. tropicalis is active during the rainy season, when it may migrate overland considerable distances to access breeding and foraging sites, often under nocturnal cover to evade predators while coexisting with in shared ponds. In the dry season, it by burrowing into mud or hiding under flat stones and dead trunks for several months, emerging with rainfall to resume activity. This aestivation strategy links to its life cycle, enabling survival in fluctuating seasonal environments.

Ecology

Behavior and diet

The Western clawed frog, Xenopus tropicalis, exhibits predominantly nocturnal activity patterns, foraging actively across aquatic environments at night while remaining largely inactive during the day. Individuals typically hide under submerged , dead trunks, or in shallow burrows along margins to avoid diurnal exposure. This is adapted to their in slow-moving or still waters, where during the rainy season, they migrate short distances to temporary pools for breeding, but retreat to riverbanks or humid refuges, burrowing into mud or under stones, during dry periods when water recedes. For prey detection, X. tropicalis relies on its well-developed system, a network of sensory organs along the body that detects vibrations and water movements from nearby prey or disturbances. This mechanosensory capability allows the frog to localize and orient toward potential food sources in murky waters without relying solely on vision. Socially, adults are generally solitary outside of breeding seasons, maintaining individual territories through aggressive displays that include claw-mediated and wrestling when intruders approach. Males occasionally produce rare, low-frequency vocalizations, such as short vibrating lasting 1–10.5 seconds at around 1 kHz, primarily during territorial disputes rather than for advertisement. Foraging in X. tropicalis involves opportunistic suction feeding, where the frog rapidly expands its broad mouth to create negative pressure, drawing in prey while using forelimbs to corral or position items closer. The diet consists primarily of aquatic invertebrates such as earthworms, insect larvae, and arthropods, supplemented by tadpoles; occurs among tadpoles. This varied, prey-size-limited intake reflects their role as generalist predators in ecosystems, with feeding efficiency enhanced by the for detecting evasive movements. X. tropicalis exhibits anti-predator responses such as rapid burrowing into substrate or adopting immobility to blend with surroundings via .

Life cycle

The life cycle of the Western clawed frog (Xenopus tropicalis) begins with egg deposition during the rainy season, typically from to August in its native West African range, when temporary pools form after heavy rains. Females lay pigmented eggs measuring approximately 0.7–0.8 mm in diameter, attached to stems and leaves in clutches often exceeding 1,000 eggs per pair. These eggs hatch within 24–26 hours at temperatures of 25–28°C, releasing embryos that develop shortly thereafter. Tadpoles emerge as gill-breathing, filter-feeding larvae that are primarily herbivorous or omnivorous, consuming , , and fine particulate matter suspended in the . They form swarms in shallow, vegetated pools and grow rapidly, with forelimbs emerging at a body length of about 17 mm (total length 42–46 mm). The stage lasts 4–6 weeks under optimal conditions, during which they rely on for oxygen and exhibit broad mouths with tentacles adapted for suspension feeding. Metamorphosis occurs when tadpoles reach a total length of less than 50 mm, marking the transition to the juvenile froglet stage over 1–2 weeks, with tail resorption completing the process. This transformation is triggered by , which regulate tissue remodeling, including the resorption of the tail and development of lungs for air breathing. Post-metamorphosis froglets measure 11.5–15.5 mm in snout-vent length and begin feeding on small within days. The entire developmental cycle from to reproductive maturity typically spans 4–6 months, with males maturing at around 22 weeks and females at 30 weeks post-metamorphosis. In the wild, X. tropicalis exhibits seasonal adaptations tied to its tropical habitat, with breeding confined to the when water bodies are available. During the , adults aestivate by burrowing into mud, hiding under stones, or retreating to humid riverbank burrows to survive , emerging with the onset of rains to initiate the next reproductive cycle.

Reproduction and genetics

Reproductive biology

The reproductive biology of Xenopus tropicalis is characterized by seasonal, externally fertilizing that occurs primarily in aquatic habitats during the rainy season. Breeding is explosive in nature, with adults migrating to temporary or semi-permanent pools and ponds following rainfall, where males vocalize to attract females and initiate . Multiple males often compete for access to receptive females through physical interactions and attempts to establish , the inguinal clasping posture in which the male grasps the female around the torso to stimulate release. This behavior typically takes place in shallow, vegetated waters such as forest pools or muddy depressions that fill with rain, providing suitable sites for spawning. Fertilization in X. tropicalis is external, with the female releasing eggs into the water while clasped in , and the male simultaneously discharging over them; eggs are and attach to submerged or the water surface. There is no after spawning, and females exhibit high , producing 1,000 to 9,000 eggs per clutch, with the potential for multiple clutches annually, enabling up to several thousand eggs per breeding season. Embryos develop externally without , hatching into tadpoles that undergo independently. Reproductive physiology is regulated by gonadotropins, which induce in females and in males; in laboratory settings, injections reliably trigger spawning. Males develop androgen-dependent nuptial pads on their forelimbs during the breeding season, aiding in grasping during ; these pads emerge with rising testosterone levels around 8 weeks post-metamorphosis. Breeding is highly seasonal, triggered by increased rainfall and warmer temperatures (typically 24–28°C), with spawning peaking from July to August in West African populations and tadpoles present throughout the rainy period.

Sex determination

The Western clawed frog (Xenopus tropicalis) employs a distinctive chromosomal characterized by three sex chromosomes—Z, W, and Y—all originating from an ancestral chromosome on linkage group 7 (corresponding to in the assembly). Males are typically homogametic ZZ but can also be heterogametic ZY or WY, while females are heterogametic ZW or homogametic WW. The W and Y chromosomes exhibit degeneration relative to the Z chromosome, marked by higher divergence, reduced gene content, and male-biased expression patterns in the sex-linked region (approximately 8–10.3 Mb on ). This degeneration reflects ongoing evolutionary processes, with the Y chromosome having arisen more recently from a Z-like , estimated at less than 25 million years ago. Sex ratios in X. tropicalis are variable, ranging from approximately 1:1 male:female under standard conditions to biased outcomes such as 1:3 male:female in specific crosses (e.g., ZW female × ZY male), primarily due to favoring certain gametes. Environmental factors, including , exert only minor influences on sex determination, with the system predominantly under genetic control rather than exhibiting strong typical of some other amphibians. Unlike mammalian systems dominated by a single such as SRY, sex determination in X. tropicalis is polygenic, lacking a master regulatory and involving multiple loci on the that interact to override feminizing or masculinizing signals (e.g., the Y-linked factor dominates over W-linked feminization). The primary sex-determining region maps to the short arm of , approximately 65 cM from the , with no evidence of a single dominant switch. This multifaceted system positions X. tropicalis as a valuable model for studying Y-chromosome , turnover, and the dynamics of heteromorphic chromosomes in vertebrates. Recent investigations, including a 2025 study on metabolic responses to warming, have highlighted sex-biased in immune pathways, demonstrating attenuation of —such as reduced female-biased expression in hepatic immune genes—under elevated temperatures, which links environmental stress to altered immune activation and potential evolutionary adaptations.

Conservation

IUCN status

The western clawed frog (Xenopus tropicalis) is classified as Least Concern (LC) on the of . This assessment, conducted in 2019 by the IUCN SSC Specialist Group, remains unchanged as of 2025, reflecting the species' overall low risk. The species meets the Least Concern criteria due to its extensive extent of occurrence exceeding 100,000 km² across forested regions of , from in the west to and the in the east. There is no evidence of severe population fragmentation or continuing decline, and X. tropicalis demonstrates tolerance to some habitat modifications, such as altered aquatic environments in agricultural landscapes. Population trends are considered stable, with estimates of more than 10,000 mature individuals across its range. Ongoing monitoring relies on data from platforms like AmphibiaWeb and the , which track distribution, occurrence records, and (e.g., ), but reveal no quantitative evidence of population declines. Xenopus tropicalis is not listed under appendices, and wild collection pressure remains low, primarily due to widespread for research purposes that reduces demand on natural populations.

Threats and management

The primary threats to Xenopus tropicalis in its native West African range stem from habitat degradation driven by and , which fragment wetlands and forest streams essential for breeding and . further exacerbates this loss, converting suitable aquatic habitats into developed areas. from agricultural pesticides and fertilizers contaminates waterways, impairing physiology and reproduction. Climate change poses an additional risk by altering seasonal rainfall patterns, potentially disrupting breeding cycles tied to wet periods in tropical savannas and forests. In introduced regions like , where established populations exist, X. tropicalis encounters invasive competitors and faces challenges that could indirectly affect global conservation efforts through spread or hybridization risks. Although harvesting for the pet and research is minor compared to other amphibians, it contributes to localized population pressures and carries risks of transmitting pathogens like the chytrid fungus , despite X. tropicalis's relative resistance to infection. Conservation management includes protection within areas like in Côte d'Ivoire, where populations persist in undisturbed forest wetlands. programs for scientific research have significantly reduced reliance on wild harvests, promoting sustainable use and genetic preservation. Ongoing monitoring in 2025 leverages citizen science platforms such as to track distributions and detect declines across . Looking ahead, warming temperatures may lead to range contraction in marginal habitats, narrowing suitable climatic envelopes. Enhanced measures for introduced populations, including removal efforts in , are critical to prevent further ecological disruptions and support native range conservation.

Research applications

Model organism advantages

The Western clawed frog, tropicalis, serves as a valuable in biological research due to its diploid , which facilitates straightforward genetic and forward genetic screens compared to polyploid relatives. This diploidy, with a of approximately 1.7 Gb, enables precise mapping of mutations and simplifies genomic analyses, unlike the pseudotetraploid of laevis. Additionally, X. tropicalis has a short generation time of 4-6 months, allowing for rapid multigenerational experiments that accelerate genetic studies. Reproductive traits further enhance its utility, including external fertilization that yields large, translucent embryos—typically thousands per clutch—ideal for high-throughput imaging and developmental observations without invasive procedures. These embryos' transparency permits real-time visualization of cellular processes, such as , using techniques like time-lapse . Husbandry of X. tropicalis is straightforward, as it is fully aquatic and thrives at around 25°C in standard laboratory aquaria, reducing maintenance costs and logistical demands relative to mammalian models. Transgenesis has been revolutionized by methods, achieving high-efficiency targeted edits since the early 2010s, including knock-ins and indels with minimal mosaicism. Compared to X. laevis, X. tropicalis breeds more rapidly and its diploid nature supports cleaner genetic inheritance, making it preferable for studies. Recent advancements, such as 2025 protocols for targeted integrations via , have improved knock-in efficiency for modeling, as demonstrated in a PNAS study creating BRAFV600E knock-in lines for and tumor . Supporting resources bolster its use, including the Xenbase database, which provides comprehensive genomic, transcriptomic, and phenotypic data for X. tropicalis. Stock centers like the National BioResource Project (NBRP) in and the National Xenopus Resource (NXR) in the distribute wild-type, , and transgenic lines, ensuring accessible and standardized strains for global researchers.

Key scientific contributions

Xenopus tropicalis has significantly advanced developmental biology through studies on gene regulation during embryogenesis, leveraging its rapid development and transparency for real-time observation of cellular processes. Researchers have utilized the species to elucidate mechanisms of transcriptional control and signaling pathways that govern early embryonic patterning, such as the role of Wnt and BMP gradients in establishing body axes. At the 20th International Xenopus Conference (IXC25) held in August 2025, key highlights included presentations on neural crest cell migration and specification, revealing conserved roles of Sox and Twist transcription factors in craniofacial development, as well as advances in organogenesis models for kidney and heart formation using live imaging techniques. In , the sequencing of the Xenopus tropicalis in 2010 marked the first complete diploid assembly, providing a 1.7 Gbp reference that bridges evolutionary gaps between and mammals with orthologs for over 79% of identified genes. This resource has enabled forward and reverse genetic screens, facilitating the identification of genes essential for vertebrate development. More recently, /Cas9 editing in X. tropicalis has established it as a model for neurodevelopmental disorders; for instance, targeted knock-ins have recapitulated variants in genes like BRAF, producing phenotypes that mirror conditions such as cardio-facio-cutaneous syndrome. A 2024 protocol further expanded this utility by demonstrating efficient modeling of patient-specific mutations across multiple loci, uncovering conserved pathogenic mechanisms. Physiological research using X. tropicalis has illuminated responses to environmental stressors, particularly in the context of . A 2025 study published in detailed metabolic acclimation to a 5°C warming shift, showing elevated , immune gene activation via pathways, and attenuated in growth rates, with females exhibiting reduced metabolic efficiency compared to males. These findings underscore the species' sensitivity to temperature as a proxy for amphibian vulnerability to global warming. Additionally, investigations into evolution have revealed that transitions from diploid to polyploid states in species, including comparisons with X. tropicalis ancestors, involve cell size increases and metabolic rate reductions, enhancing survival in hypoxic environments through altered expression. Beyond core areas, X. tropicalis contributes to by serving as a standardized for developmental , where embryonic exposure to pollutants like perfluorooctanesulfonate disrupts hormone signaling and axial patterning, informing regulatory guidelines. In stem cell research, explant cultures from X. tropicalis embryos have generated immortal cell lines expressing pluripotency markers like Oct4, enabling high-throughput screens for neural differentiation factors. The species also informs vertebrate (evo-devo), notably through studies of limb bud initiation; despite lacking free-swimming larval limbs, genetic manipulations reveal networks that parallel limb evolution, highlighting latent developmental potential. Recent integrative efforts include a 2025 review in marking 25 years of Xenbase, which has centralized over 4 GB of genomic, expression, and phenotypic data from X. tropicalis, accelerating discoveries in disease modeling and evo-devo by linking orthologous human genes. A concurrent 2025 global study on emphasized risks from the international trade of Xenopus species, which has contributed to the spread of pathogens like the deadly Chytrid fungus, potentially affecting research and underscoring the need for sustainable sourcing.

References

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  12. https://pubmed.ncbi.nlm.nih.gov/30737699/
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  14. https://pmc.ncbi.nlm.nih.gov/articles/PMC2878287/
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  16. https://pmc.ncbi.nlm.nih.gov/articles/PMC3863417/
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  18. https://pmc.ncbi.nlm.nih.gov/articles/PMC10828168/
  19. https://pmc.ncbi.nlm.nih.gov/articles/PMC3621785/
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