Genetic insight into a polygenic trait using a novel genome-wide association approach in a wild amphibian population.

Body size variation is central in the evolution of life-history traits in amphibians, but the underlying genetic architecture of this complex trait is still largely unknown. Herein, we studied the genetic basis of body size and fecundity of the alternative morphotypes in a wild population of the Greek smooth newt (Lissotriton graecus). By combining a genome-wide association approach with linkage disequilibrium network analysis, we were able to identify clusters of highly correlated loci thus maximizing sequence data for downstream analysis. The putatively associated variants explained 12.8% to 44.5% of the total phenotypic variation in body size and were mapped to genes with functional roles in the regulation of gene expression and cell cycle processes. Our study is the first to provide insights into the genetic basis of complex traits in newts and provides a useful tool to identify loci potentially involved in fitness-related traits in small data sets from natural populations in non-model species.

Comparison of hypoxia- and hyperoxia-induced alteration of epigene expression pattern in lungs of Pleurodeles waltl and Mus musculus.

Epigenetics is an emerging field of research because of its involvement in susceptibility to diseases and aging. Hypoxia and hyperoxia are known to be involved widely in various pathophysiologies. Here, we compared the differential epigene expression pattern between Pleurodeles waltl and Mus musculus (commonly known as Iberian ribbed newt and mouse, respectively) exposed to hypoxia and hyperoxia. Adult healthy newts and mice were exposed to normobaric hypoxia (8% O2) and hyperoxia (80% O2) for 2 hours. We collected the lungs and analyzed the expression of hypoxia-inducible factor 1 alpha (Hif1α) and several key epigenes from DNA methyltransferase (DNMT) family, histone deacetylase (HDAC) family, and methyl-CpG binding domain (MBD) family. The exposure to hypoxia significantly increased the mRNA levels of DNA methyltransferase 3 alpha (Dnmt3α), methyl-CpG binding domain protein 2 (Mbd2), Mbd3, and histone deacetylase 2 (Hdac2) in lungs of newts, but decreased the mRNA levels of DNA methyltransferase 1 (Dnmt1) and Dnmt3α in lungs of mice. The exposure to hyperoxia did not significantly change the expression of any gene in either newts or mice. The differential epigene expression pattern in response to hypoxia between newts and mice may provide novel insights into the prevention and treatment of disorders developed due to hypoxia exposure.

Amphibian newts as experimental models for studying weight gain after castration.

Vertebrate animals often exhibit sexual dimorphism in body shape. In mammals, decreases in sex hormones caused by testicular castration can affect body shape and occasionally lead to pathologies such as obesity. Post-castration obesity can also be problematic for the health of companion animals, including non-mammals. In order to understand the mechanism of post-castration obesity in vertebrates other than mammals, experimental models are required. We examined whether the Iberian ribbed newt, which has recently become a popular experimental model for amphibian research, could serve as a model for analyzing changes in body shape after castration. In newts, new testes can be regenerated after removal of differentiated testes. We analyzed changes in body shape by removing the testes under conditions in which they could regenerate or conditions in which they could not regenerate. Removal of the testes reduced blood testosterone levels. The body weight and abdominal girth of the newts were increased compared with normal male newts. Transcriptome analysis of the liver showed that a set of genes related to lipid metabolism was continuously up-regulated in castrated newts. Our study suggests that changes in body shape after castration are common in vertebrates. Iberian ribbed newts are thus a suitable model for comparative studies of the long-term physiologic- and endocrine-level effects of castration.

Widespread introgression of MHC genes in Iberian Podarcis lizards.

Major histocompatibility complex (MHC) genes are crucial for the adaptive immune response of jawed vertebrates. Their variation, reaching extreme levels, is driven mainly by an arms race between hosts and pathogens. One hypothesised mechanism contributing to MHC polymorphism is adaptive introgression, the exchange of genetic variants between hybridising species favoured by selection, yet its effect on MHC variation is poorly understood. Detection of adaptive MHC introgression, though challenging, may be facilitated by the analysis of species complexes forming multiple hybrid zones. Here, we investigated MHC introgression in six hybrid zones formed by seven species of Podarcis lizards inhabiting the Iberian Peninsula. To differentiate adaptive introgression from neutral introgression, we compared the patterns of gene exchange in MHC and genome-wide markers. We found elevated sharing of MHC alleles in the proximity of contact beyond the areas of detectable genome-wide admixture in most hybrid zones and, in half of them, asymmetric MHC exchange. In general, the elevated MHC allele sharing between species pairs with abutting ranges compared to geographically isolated species pairs also supports the prevalence of introgression. Collectively, our results demonstrate widespread MHC introgression in the Iberian Podarcis complex and suggest its adaptiveness. Contrary to previous results from Triturus newts, we did not observe differences in the rate of introgression between MHC classes. Our work adds support to the emerging view of adaptive introgression as a key mechanism shaping MHC diversity. It also raises questions about the effect of elevated MHC variation and factors leading to the asymmetry of adaptive introgression.

Identification and characterization of sperm motility-initiating substance-2 gene in internally fertilizing Cynops species.

Sperm motility-initiating substance (SMIS) is an oviductal protein critical for internal fertilization in urodeles. It contributes to the establishment of various reproductive modes in amphibians and is thus a unique research model for the gene evolution of gamete-recognizing ligands that have diversified among animal species. In this study, a paralogous SMIS gene, smis2, was identified via the RNA sequencing of the oviduct of the newt, Cynops pyrrhogaster. The base sequence of the smis2 gene was homologous (˃90%) to that of the original smis gene (smis1), and deduced amino acid sequences of both genes conserved six cysteine residues essential for the cysteine knot motif. Furthermore, smis2 complementary DNA was identified in the oviduct of Cynops ensicauda, and the base substitution patterns also suggested that the smis gene was duplicated in the Salamandridae. Nonsynonymous/synonymous substitution ratios of smis1 and smis2 genes were 0.79 and 2.6, respectively, suggesting that smis2 gene evolution was independently driven by positive selection. Amino acid substitutions were concentrated in the cysteine knot motif of SMIS2. The smis2 gene was expressed in some organs in addition to the oviduct; in contrast, SMIS1 was only expressed in the oviduct. The SMIS2 protein was suggested to be produced and secreted at least in the oviduct and redundantly act in sperm. These results suggest that smis1 plays the original role in the oviduct, whereas smis2 may undergo neofunctionalization, which rarely occurs in gene evolution.

Landscape genetics reveals contrasting patterns of connectivity in two newt species (Lissotriton montandoni and L. vulgaris).

Ecologically distinct species may respond to landscape changes in different ways. In addition to basic ecological data, the extent of the geographic range has been successfully used as an indicator of species sensitivity to anthropogenic landscapes, with widespread species usually found to be less sensitive compared to range-restricted species. In this study, we investigate connectivity patterns of two closely related but ecologically distinct newt species - the range-restricted, Lissotriton montandoni and the widespread, L. vulgaris - using genomic data, a highly replicated setting (six geographic regions per species), and tools from landscape genetics. Our results show the importance of forest for connectivity in both species, but at the same time suggest differential use of forested habitat, with L. montandoni and L. vulgaris showing the highest connectivity at forest-core and forest-edges, respectively. Anthropogenic landscapes (i.e., higher crop- or urban-cover) increased resistance in both species, but the effect was one to three orders of magnitude stronger in L. montandoni than in L. vulgaris. This result is consistent with a view of L. vulgaris as an ecological generalist. Even so, currently, the negative impact of anthropogenic landscapes is mainly seen in connectivity among L. vulgaris populations, which show significantly stronger isolation and lower effective sizes relative to L. montandoni. Overall, this study emphasizes how habitat destruction is compromising genetic connectivity not only in endemic, range-restricted species of conservation concern but also in widespread generalist species, despite their comparatively lower sensitivity to anthropogenic landscape changes.

Interspecific introgression of MHC genes in Triturus newts: Evidence from multiple contact zones.

The major histocompatibility complex (MHC) genes are central to the adaptive immune response in vertebrates. Selection generally maintains high MHC variation because the spectrum of recognized pathogens depends on MHC polymorphism. Novel alleles favoured by selection originate by interallelic recombination or de novo mutations but may also be acquired by introgression from related species. However, the extent and prevalence of MHC introgression remain an open question. In this study, we tested for MHC introgression in six hybrid zones formed by six Triturus newt species. We sequenced and genotyped the polymorphic second exons of the MHC class I and II genes and compared their interspecific similarity at various distances from the centre of the hybrid zone. We found evidence for introgression of both MHC classes in the majority of examined hybrid zones, with support for a more substantial class I introgression. Furthermore, the overall MHC allele sharing outside of hybrid zones was elevated between pairs of Triturus species with abutting ranges, regardless of the phylogenetic distance between them. No effect of past hybrid zone movement on MHC allele sharing was found. Finally, using previously published genome-wide data, we demonstrated that MHC introgression was more extensive than genome-wide introgression, supporting its adaptive potential. Our study thus provides evidence for the prevalence of MHC introgression across multiple Triturus hybrid zones, indicating that MHC introgression between divergent hybridizing species may be widespread and adaptive.

Characterization, Comparison of Two New Mitogenomes of Crocodile Newts Tylototriton (Caudata: Salamandridae), and Phylogenetic Implications.

Mitochondrial genomes (mitogenomes) are valuable resources in molecular and evolutionary studies, such as phylogeny and population genetics. The complete mitogenomes of two crocodile newts, Tylototriton broadoridgus and Tylototriton gaowangjienensis, were sequenced, assembled, and annotated for the first time using next-generation sequencing. The complete mitogenomes of T. broadoridgus and T. gaowangjienensis were 16,265 bp and 16,259 bp in lengths, which both composed of 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNA genes, and 1 control region. The two mitogenomes had high A + T content with positive AT-skew and negative GC-skew patterns. The ratio of non-synonymous and synonymous substitutions showed that, relatively, the ATP8 gene evolved the fastest and COI evolved the slowest among the 13 PCGs. Phylogenetic trees from BI and ML analyses resulted in identical topologies, where the Tylototriton split into two groups corresponding to two subgenera. Both T. broadoridgus and T. gaowangjienensis sequenced here belonged to the subgenus Yaotriton, and these two species shared a tentative sister group relationship. The two mitogenomes reported in this study provided valuable data for future molecular and evolutionary studies of the genus Tylotoriton and other salamanders.

Comparative multi-locus assessment of modern Asian newts ( Cynops, Paramesotriton, and Pachytriton: Salamandridae) in southern China suggests a shared biogeographic history.

Evolutionary biologists are always interested in deciphering the geographic context of diversification, therefore they introduced the concept of comparative phylogeography, which helps to identify common mechanisms that contribute to shared genetic structures among organisms from the same region. Here, we used multi-locus genetic data along with environmental data to investigate shared phylogeographic patterns among three Asian-endemic newt genera, Cynops, Paramesotriton and Pachytriton, which occurred in montane/submontane streams or ponds in southern China. Our 222 samples from 78 localities covered the entire range of the three genera and represented the largest dataset of this group to date. We reconstructed matrilineal genealogies from two protein-coding, mitochondrial genes, and gene network from two nuclear genes. We also estimated divergence times of major cladogenetic events and used occurrence data to evaluate niche difference and similarity between lineages. Our results revealed a common basal split in all three genera that corresponds to the separation of two geographic terrains of southern China. Those ancient divergence occurred during middle to late Miocene and likely correlate with paleoclimatic fluctuations caused by the uplift of the Qinghai-Xizang (Tibet) Plateau (QTP). Particularly, the strengthening and weakening of Asian summer monsoons during the Miocene may have profoundly impacted southern China and led to repeatedly vicariance in those newts. However, despite differences in realized niches between lineages, there is no evidence for divergence of fundamental niches. Preservation of old newt matriline lineages in mountains of southern China suggests that the region acts as both museums and cradles of speciation. Based on those results, we advocate a multi-pronged protection strategy for newts in the three genera.

Phylogenetic analysis of combined mitochondrial genome and 32 nuclear genes provides key insights into molecular systematics and historical biogeography of Asian warty newts of the genus Paramesotriton (Caudata: Salamandridae).

The Paramesotriton Chang, 1935 genus of Asian warty newts is the second most diverse genus in the family Salamandridae, currently containing 14 recognized species from northern Vietnam to southwest-central and southern China. Although species of this genus have been included in previous phylogenetic studies, the origin and interspecific relationships of the genus are still not fully resolved, especially at key nodes in the phylogeny. In this study, we sequenced mitochondrial genomes and 32 nuclear genes from 27 samples belonging to 14 species to reconstruct the interspecific phylogenetic relationships within Paramesotriton and explore its historical biogeography in southern China. Both Bayesian inference and maximum-likelihood analyses highly supported the monophyly of Paramesotriton and its two recognized species groups ( P. caudopunctatus and P. chinensis groups) and further identified five hypothetical phylogenetic cryptic species. Biogeographic analyses indicated that Paramesotriton originated in southwestern China (Yunnan-Guizhou Plateau/South China) during the late Oligocene. The time of origin of Paramesotriton corresponded to the second uplift of the Himalayan/Qinghai-Xizang (Tibetan) Plateau (QTP), rapid lateral extrusion of Indochina, and formation of karst landscapes in southwestern China. Principal component analysis (PCA), independent sample t-tests, and niche differentiation using bioclimatic variables based on locations of occurrence suggested that Paramesotriton habitat conditions in the three current regions (West, South, and East) differ significantly, with different levels of climatic niche differentiation. Species distribution model (SDM) predictions indicated that the most suitable distribution areas for the P. caudopunctatus and P. chinensis species groups are western and southern/eastern areas of southern China. This study increases our knowledge of the taxonomy, biodiversity, origin, and suitable distribution areas of the genus Paramesotriton based on phylogenetic, biogeographic, and species distribution models.

Identification of motilin in Japanese fire bellied newt.

Motilin, a peptide hormone consisting of 22 amino acid residues, was identified in the duodenum of pigs in the 1970s. It is known to induce gastrointestinal contractions during the interdigestive state in mammals. Although the motilin gene has been identified in various animal species, it has not been studied in amphibians. Here, we identified the motilin gene in the Japanese fire bellied newt (Cynops pyrrhogaster), and conducted an analysis of tissue distribution, morphological observations, and physiological experiments. The deduced mature newt motilin comprises 22 amino acid residues, like in mammals and birds. The C-terminus of the newt motilin showed high homology with motilin from other species compared to the N-terminus region, which is considered the bioactive site. Motilin mRNA expression in newts was abundant in the upper small intestine, with notably high motilin mRNA expression found in the pancreas. Motilin-producing cells were found in the mucosal layer of the upper small intestine and existed as two cell types: open-and closed-type cells. Motilin-producing cells in the pancreas were also found to produce insulin but not glucagon. Newt motilin stimulated gastric contractions but not in other parts of the intestines in vitro, and motilin-induced gastric contraction was significantly inhibited by treatment with atropine, a muscarinic acetylcholine receptor antagonist. These results indicate that motilin is also present in amphibians, and that its gastrointestinal contractile effects are conserved in mammals, birds, and amphibians. Additionally, we demonstrated for the first time the existence of pancreatic motilin, suggesting that newt motilin has an additional unknown physiological role.

Newt Hoxa13 has an essential and predominant role in digit formation during development and regeneration.

The 5'Hox genes play crucial roles in limb development and specify regions in the proximal-distal axis of limbs. However, there is no direct genetic evidence that Hox genes are essential for limb development in non-mammalian tetrapods or for limb regeneration. Here, we produced single to quadruple Hox13 paralog mutants using the CRISPR/Cas9 system in newts (Pleurodeles waltl), which have strong regenerative capacities, and also produced germline mutants. We show that Hox13 genes are essential for digit formation in development, as in mice. In addition, Hoxa13 has a predominant role in digit formation, unlike in mice. The predominance is probably due to the restricted expression pattern of Hoxd13 in limb buds and the strong dependence of Hoxd13 expression on Hoxa13. Finally, we demonstrate that Hox13 genes are also necessary for digit formation in limb regeneration. Our findings reveal that the general function of Hox13 genes is conserved between limb development and regeneration, and across taxa. The predominance of Hoxa13 function both in newt limbs and fish fins, but not in mouse limbs, suggests a potential contribution of Hoxa13 function in fin-to-limb transition.

A lot of convergence, a bit of divergence: Environment and interspecific interactions shape body colour patterns in Lissotriton newts.

Coexistence with related species poses evolutionary challenges to which populations may react in diverse ways. When exposed to similar environments, sympatric populations of two species may adopt similar phenotypic trait values. However, selection may also favour trait divergence as a way to reduce competition for resources or mates. The characteristics of external body parts, such as coloration and external morphology, are involved to varying degrees in intraspecific signalling as well as in the adaptation to the environment and consequently may be diversely affected by interspecific interactions in sympatry. Here, we studied the effect of sympatry on various colour and morphological traits in males and females of two related newt species Lissotriton helveticus and L. vulgaris. Importantly, we did not only estimate how raw trait differences between species respond to sympatry, but also the marginal responses after controlling for environmental variation. We found that dorsal and caudal coloration converged in sympatry, likely reflecting their role in adaptation to local environments, especially concealment from predators. In contrast, aspects of male and female ventral coloration, which harbours sexual signals in both species, diverged in sympatry. This divergence may reduce opportunities for interspecific sexual interactions and the associated loss of energy, suggesting reproductive character displacement (RCD). Our study emphasizes the contrasting patterns of traits involved in different functions and calls for the need to consider this diversity in evolutionary studies.

Genetic traces of hybrid zone movement across a fragmented habitat.

Theoretical and empirical studies suggest that the structure and position of hybrid zones can change over time. Evidence for moving hybrid zones has been directly inferred by repeated sampling over time, or indirectly through the detection of genetic footprints left by the receding species and the resulting asymmetric patterns of introgression across markers. We here investigate a hybrid zone formed by two subspecies of the Iberian golden-striped salamander, Chioglossa lusitanica, using a panel of 35 nuclear loci (31 SNPs and 4 allozymes) and one mitochondrial locus in a transect in central Portugal. We found concordant and coincident clines for most of the nuclear loci (n = 22, 63%), defining a narrow hybrid zone of ca. 6 km wide, with the centre positioned ca. 15 km south of the Mondego River. Asymmetric introgression was observed at another 14 loci. Their clines are displaced towards the north, with positions located either close to the Mondego River (n = 6) or further northwards (n = 8). We interpret these profiles as genetic traces of the southward displacement of C. lusitanica lusitanica by C. l. longipes over the wider Mondego River valley. We noted the absence of significant linkage disequilibrium, and we inferred low levels of effective selection per locus against hybrids, suggesting that introgression in the area of species replacement occurred under a neutral diffusion process. A species distribution model suggests that the C. lusitanica hybrid zone coincides with a narrow corridor of fragmented habitat. From the position of the displaced clines, we infer that patches of locally suitable habitat trapped some genetic variants that became disassociated from the southward moving hybrid zone. This study highlights the influence of habitat availability on hybrid zone movement.

Cryo-injury procedure-induced cardiac regeneration shows unique gene expression profiles in the newt Pleurodeles waltl.

BACKGROUND: Cardiac regeneration in the adult mouse is not substantial. Some vertebrates, such as newts and zebrafish, regenerate the heart throughout their lives. To understand how regenerative abilities differ among animal species, comparative research has been conducted in animals like mouse, zebrafish, and newt. For those purposes, cryo-injury is suitable as an experimental model for the pathological condition of human myocardial infarction. In fact, cryo-injury procedures are common in mouse and zebrafish. RESULTS: In the present study, we induced cryo-damage on the ventricle in Iberian ribbed newts using a liquid nitrogen-chilled probe. We observed that the injured area recovered within 8 weeks, with remodeling of scar tissue and proliferation of cardiomyocytes. We investigated the subsequent recovery of cryo-injured and amputated tissues by comparative analysis of the gene expression profiles following these two procedures. CONCLUSIONS: Notably, we established a cryo-injury procedure for the newt and confirmed that regeneration of the cryo-damaged myocardial tissue is achieved by changes in gene expression that are milder than those observed in the amputation model. Our results suggest that the cryo-injury method is suitable for comparing the process of cardiac regeneration in the newt with that in other animal models.

Rapid genetic divergence and mitonuclear discordance in the Taliang knobby newt ( Liangshantriton taliangensis, Salamandridae, Caudata) and their driving forces.

The Hengduan Mountains Region (HMR) is the largest "evolutionary frontier" of the northern temperate zone, and the origin and maintenance of species in this area is a research hotspot. Exploring species-specific responses to historical and contemporary environmental changes will improve our understanding of the role of this region in maintaining biodiversity. In this study, mitochondrial and microsatellite diversities were used to assess the contributions of paleogeological events, Pleistocene climatic oscillations, and contemporary landscape characteristics to the rapid intraspecific diversification of Liangshantriton taliangensis, a vulnerable amphibian species endemic to several sky-island mountains in the southeastern HMR. Divergence date estimations suggested that the East Asian monsoon, local uplifting events (Xigeda Formation strata), and Early-Middle Pleistocene transition (EMPT) promoted rapid divergence of L. taliangensis during the Pleistocene, yielding eight mitochondrial lineages and six nuclear genetic lineages. Moreover, population genetic structures were mainly fixed through isolation by resistance. Multiple in situ refugia were identified by ecological niche models and high genetic diversity, which played crucial roles in the persistence and divergence of L. taliangensis during glacial-interglacial cycles. Dramatic climatic fluctuations further promoted recurrent isolation and admixing of populations in scattered glacial refugia. The apparent mitonuclear discordance was likely the result of introgression by secondary contact and/or female-biased dispersal. Postglacial expansion generated two major secondary contact zones (Ganluo (GL) and Chuhongjue (CHJ)). Identification of conservation management units and dispersal corridors offers important recommendations for the conservation of this species.

A study on the genetic population structure and the tetrodotoxin content of rough-skinned newts, Taricha granulosa (Salamandridae), from their northern range of distribution.

Rough-skinned newts, Taricha granulosa, which contain tetrodotoxin (TTX), a potent neurotoxin, are widely distributed along the west-coast of North America up to British Columbia (BC), Canada, and Southeast Alaska. Their genetic population structure using DNA-microsatellites and the TTX-content of specimens from British Columbia (Prince Rupert area) and Alaska (Revillagigedo Island, Shelter Island, and Juneau) were analysed. TTX-concentrations were low in newts from BC and Revillagigedo Island, but high in specimens from mainland Juneau, which had been deliberately introduced from Shelter Island, where TTX was not detectable in the individuals sampled. No significant genetic differences were detected between these populations, which may correlate with the high intraspecies variability of TTX. It is still an open question, which factors favour or induce the toxin production in the newts.

Next-generation phylogeography of the banded newts (Ommatotriton): A phylogenetic hypothesis for three ancient species with geographically restricted interspecific gene flow and deep intraspecific genetic structure.

Technological developments now make it possible to employ many markers for many individuals in a phylogeographic setting, even for taxa with large and complex genomes such as salamanders. The banded newt (genus Ommatotriton) from the Near East has been proposed to contain three species (O. nesterovi, O. ophryticus and O. vittatus) with unclear phylogenetic relationships, apparently limited interspecific gene flow and deep intraspecific geographic mtDNA structure. We use parallel tagged amplicon sequencing to obtain 177 nuclear DNA markers for 35 banded newts sampled throughout the range. We determine population structure (with Bayesian clustering and principal component analysis), interspecific gene flow (by determining the distribution of species-diagnostic alleles) and phylogenetic relationships (by maximum likelihood inference of concatenated sequence data and based on a summary-coalescent approach). We confirm that the three proposed species are genetically distinct. A sister relationship between O. nesterovi and O. ophryticus is suggested. We find evidence for introgression between O. nesterovi and O. ophryticus, but this is geographically limited. Intraspecific structuring is extensive, with the only recognized banded newt subspecies, O. vittatus cilicensis, representing the most distinct lineage below the species level. While mtDNA mostly mirrors the pattern observed in nuclear DNA, all banded newt species show mito-nuclear discordance as well.

Identification and expression analysis of Dazl homologue in Cynops cyanurus.

The Dazl (deleted in azoospermia-like) gene encodes an RNA-binding protein containing an RNA recognition motif (RRM) and a DAZ motif. Dazl is essential for gametogenesis in vertebrates. In this study, we report the cloning of Dazl cDNA from Cynops cyanurus. Ccdazl mRNA showed a germline-specific expression pattern as expected. Ccdazl expression gradually decreased during oogenesis, suggesting that it may be involved in oocyte development. Phylogenetic analysis revealed that the Ccdazl protein shares conserved motifs/domains with Dazl proteins from other species. Cloning of Ccdazl provides a new tool to carry out comparative studies of germ cell development in amphibians.

Investigation of the activity of transposable elements and genes involved in their silencing in the newt Cynops orientalis, a species with a giant genome.

Caudata is an order of amphibians with great variation in genome size, which can reach enormous dimensions in salamanders. In this work, we analysed the activity of transposable elements (TEs) in the transcriptomes obtained from female and male gonads of the Chinese fire-bellied newt, Cynops orientalis, a species with a genome about 12-fold larger than the human genome. We also compared these data with genomes of two basal sarcopterygians, coelacanth and lungfish. In the newt our findings highlighted a major impact of non-LTR retroelements and a greater total TE activity compared to the lungfish Protopterus annectens, an organism also characterized by a giant genome. This difference in TE activity might be due to the presence of young copies in newt in agreement also with the increase in the genome size, an event that occurred independently and later than lungfish. Moreover, the activity of 33 target genes encoding proteins involved in the TE host silencing mechanisms, such as Ago/Piwi and NuRD complex, was evaluated and compared between the three species analysed. These data revealed high transcriptional levels of the target genes in both newt and lungfish and confirmed the activity of NuRD complex genes in adults. Finally, phylogenetic analyses performed on PRDM9 and TRIM28 allowed increasing knowledge about the evolution of these two key genes of the NuRD complex silencing mechanism in vertebrates. Our results confirmed that the gigantism of the newt genomes may be attributed to the activity and accumulation of TEs.