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The modular organization of tetrapod paired limbs and girdles, influenced by the expression of Hox genes is one of the primary driving forces of the evolution of animal locomotion. The increased morphological diversification of the paired limbs is correlated with reduced between-limb covariation, while correlation within the elements is usually higher than between the elements. The tailed amphibians, such as Lissotriton newts, have a biphasic lifestyle with aquatic and terrestrial environments imposing different constraints on limb skeleton. By employing the methods of computerized microtomography and 3D geometric morphometrics, we explored the pattern of morphological variation, disparity, modularity and morphological integration in the proximal parts of the anterior limbs of six species of Eurasian small bodied newts. Although the species significantly differ in limb shape, there is a great overlap in morphology of scapula and humerus, and there are no differences in morphological disparity. For the scapula, the shape differences related to the duration of the aquatic period are in length, depth and curvature. The shape of the humerus is not affected by the length of aquatic period, and shape differences between the species are related to robustness of the body. The length of aquatic period has statistically supported phylogenetic signal. The scapula and humerus are structures of varying modularity. For the humerus, the strongest support on the phylogenetic level was for the capitulum/shaft hypothesis, which can also be interpreted as functional modularity. For the scapula, the greatest support was for the antero-posterior hypothesis of modularity in case of Lissotriton vulgaris, which can be explained by different functional roles and muscle insertion patterns, while there was no phylogenetic modularity. The modularity patterns seem to correspond with the general tetrapod pattern, with modularity being more pronounced in the distal structure. The future research should include more salamandrid taxa with different habitat preferences and both adult and larval stages, in order to explore how size, phylogeny and ecology affect the morphology and covariation patterns of limbs., (© 2024 Anatomical Society.)

A new species of the genus Tylototriton sensu lato from Tongzi County, Guizhou Province, China was described. Molecular phylogenetic analyses based on mitochondrial 16S and ND2 gene sequences indicated the new species as the most closely related species of T. dabienicus in Henan. The new species could be identified from its congeners by a combination of the following morphological characters: (1) body size medium (TOL 120.5135.1 mm and SVL 61.165.9 mm in males, and TOL 123.5127.6 mm and SVL 66.769.2 mm in females); (2) gular fold present; (3) the tail length shorter than the snout-vent length; (4) the distal ends and ventral surfaces of digits, peripheral area of cloaca, and the lower margin of tail orange; (5) the distal tips of the limbs greatly overlapping when the fore and hind limbs being pressed along the trunk; (6) fingertips reaching to the level beyond the snout when the forelimbs being stretched forward; (7) nodule-like warts on body sides continuous and no obvious. The new species is known only from the montane forests of Huanglian Nature Reserve, Tongzi County, Guizhou Province, China. We recommend the new species to be listed as Critically Endangered.

Salamandrina perspicillata, from Northern and Central Italy, and Salamandrina terdigitata, from Southern Italy, represent a unique case of endemism among the amphibians of Europe. Some efforts were made to study the biology and ecology of these species, but only few studies focused on their comparative osteology. In particular, detailed descriptions of isolated skeletal elements and comparisons with other European urodeles are not available in literature hindering the identification of their fossils that testify for an ancient much broader range. The correct identification of fossil remains, mostly based on careful osteological descriptions, is fundamental to study the evolution of the range of this genus through time and the origin of the current endemic condition. This work is focused on the description of selected skeletal elements (occipito-otic complex, limb bones, atlas, trunk, sacral, caudosacral and caudal vertebrae) of dry-prepared skeletons and CT-scans of wet preserved specimens, which are the most common in the fossil record. We provide osteological comparison of Salamandrina with other genera of Europe, yielding diagnostic characters which allow the identification of fossils at a generic level. No significant differences between the two species S. perspicillata and S. terdigitata were found in the described skeletal elements, thus, the identification of skeletal elements at the species level is, at the moment, impossible., (© 2020 Wiley Periodicals LLC.)

The diversity of the vertebrate cranial shape of phylogenetically related taxa allows conclusions on ecology and life history. As pleurodeline newts (the genera Echinotriton, Pleurodeles and Tylototriton) have polymorphic reproductive modes, they are highly suitable for following cranial shape evolution in relation to reproduction and environment. We investigated interspecific differences externally and differences in the cranial shape of pleurodeline newts via two-dimensional geometric morphometrics. Our analyses also included the closely related but extinct genus Chelotriton to better follow the evolutionary history of cranial shape. Pleurodeles was morphologically distinct in relation to other phylogenetically basal salamanders. The subgenera within Tylototriton (Tylototriton and Yaotriton) were well separated in morphospace, whereas Echinotriton resembled the subgenus Yaotriton more than Tylototriton. Oviposition site choice correlated with phylogeny and morphology. Only the mating mode, with a random distribution along the phylogenetic tree, separated crocodile newts into two morphologically distinct groups. Extinct Chelotriton likely represented several species and were morphologically and ecologically more similar to Echinotriton and Yaotriton than to Tylototriton subgenera. Our data also provide the first comprehensive morphological support for the molecular phylogeny of pleurodeline newts., (© 2020 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Climate change-induced extinctions are estimated to eliminate one in six known species by the end of the century. One major factor that will contribute to these extinctions is extreme climatic events. Here, we show the ecological impacts of recent record warm air temperatures and simultaneous peak drought conditions in California. From 2008-2016, the southern populations of a wide-ranging endemic amphibian (the California newt, Taricha torosa) showed a 20% reduction to mean body condition and significant losses to variation in body condition linked with extreme climate deviations. However, body condition in northern populations remained relatively unaffected during this period. Range-wide population estimates of change to body condition under future climate change scenarios within the next 50 years suggest that northern populations will mirror the loss of body condition recently observed in southern populations. This change is predicated on latter 21 st century climate deviations that resemble recent conditions in Southern California. Thus, the ecological consequences of climate change have already occurred across the warmer, drier regions of Southern California, and our results suggest that predicted climate vulnerable regions in the more mesic northern range likely will not provide climate refuge for numerous amphibian communities.

The diversity of trunk muscle morphology of Salamandridae occupying different habitats (aquatic: Pachytriton labiatus ; terrestrial: Tylototriton kweichowensis and Salamandra salamandra salamandra ) was examined. Trunk muscles were dissected, and muscle weight ratios were quantified. The terrestrial species have larger abdominal trunk muscles than the aquatic species do. In contrast, the lateral hypaxial muscles are larger in the aquatic species. The M. rectus abdominis profundus is located subjacent to the M. rectus abdominis in the terrestrial species. In the aquatic species, the ventral muscle is composed of the M. rectus abdominis alone. The lateral hypaxial muscles in the aquatic species are suited to lateral bending during underwater locomotion in the denser aquatic medium. Larger abdominal muscles may be used in supporting body weight against gravity in the terrestrial species. The function of the M. rectus abdominis profundus may be to support the M. rectus abdominis in the terrestrial species. These findings suggest a divergent evolution of trunk muscle characteristics within the Salamandridae, which correlate with both habitats and modes of locomotion., (© 2019 Zoological Society of Japan.)

We describe a new species of the genus Tylototriton from Ingyin Taung Mt., Mohnyin Township, Kachin State, Myanmar, based on morphological and molecular evidence. The new species is assigned to the subgenus Tylototriton s. str. and is clearly distinct from all known congeners by the following characters: medium body size; thin, long tail, lacking lateral grooves; rough skin; truncate snout; wide, protruding supratemporal bony ridges on head, beginning at anterior corner of orbit; weak, almost indistinct sagittal ridge; long, thin limbs, broadly overlapping when adpressed along body; distinct, wide, non-segmented vertebral ridge; 13 or 14 rib nodules; brown to dark-brown background coloration with dull orange-brown to yellowish-brown markings on labial regions, parotoids, rib nodules, whole limbs, vent, and ventral tail ridge. We also briefly discuss biogeography and species diversity of the genus Tylototriton in Myanmar.

Nonylphenol ethoxylates (NPEs) are well known endocrine disruptors. Widespread environmental contamination from NPEs is an issue of great concern. Despite amphibians are often exposed to such contaminants, very little attention has been dedicated to this vertebrate group. No information is available on the effects of NPEs onto the amphibian skin and only few reports have been conducted on fish. Here, histological and ultrastructural modifications of the skin have been evaluated in the Italian newt Lissotriton italicus. After a short-term exposure to two ecologically relevant concentrations of NP, severe pathological alterations, both dose and time-dependent, have been observed. The main effects were an increased mucous secretion, the dilation of the endomembrane, the wrinkling of the epidermal surface, the appearance of tubercles, the increased cellular turnover, continuous shedding processes. Some of the described skin alterations can easily interfere with physiological functions, such as osmoregulation and body protection, with detrimental consequences for the amphibian populations., (Copyright © 2018 Elsevier B.V. All rights reserved.)

We carried out a comparative morphometric analysis of 56 species of salamandrid salamanders, representing 19 out of 21 extant genera, with the aim of uncovering the major patterns of skull shape diversification, and revealing possible trends and directions of evolutionary change. To do this we used micro-computed tomography scanning and three-dimensional geometric morphometrics, along with a well-resolved molecular phylogeny. We found that allometry explains a relatively small amount of shape variation across taxa. Congeneric species of salamandrid salamanders are more similar to each other and cluster together producing distinct groups in morphospace. We detected a strong phylogenetic signal and little homoplasy. The most pronounced changes in the skull shape are related to the changes of the frontosquamosal arch, a unique feature of the cranial skeleton for the family Salamandridae, which is formed by processes arising from the frontal and squamosal bones that arch over the orbits. By mapping character states over the phylogeny, we found that a reduction of the frontosquamosal arch occurs independently in three lineages of the subfamily Pleurodelinae. This reduction can probably be attributed to changes in the development and ossification rates of the frontosquamosal arch. In general, our results are similar to those obtained for caecilian amphibians, with an early expansion into the available morphospace and a complex history characterizing evolution of skull shape in both groups. To evaluate the specificity of the inferred evolutionary trajectories and Caudata-wide trends in the diversity of skull morphology, information from additional groups of tailed amphibians is needed., (© 2017 Anatomical Society.)

Histochemical organization of the Caudata olfactory system remains largely unknown, despite this amphibian order showing phylogenetic diversity in the development of the vomeronasal organ and its primary centre, the accessory olfactory bulb. Here, we investigated the glycoconjugate distribution in the olfactory bulb of a semi-aquatic salamander, the Japanese sword-tailed newt (Cynops ensicauda), by histochemical analysis of the lectins that were present. Eleven lectins showed a specific binding to the olfactory and vomeronasal nerves as well as to the olfactory glomeruli. Among them, succinylated wheat germ agglutinin (s-WGA), soya bean agglutinin (SBA), Bandeiraea simplicifolia lectin-I (BSL-I) and peanut agglutinin showed significantly different bindings to glomeruli between the main and accessory olfactory bulbs. We also found that s-WGA, SBA, BSL-I and Pisum sativum agglutinin preferentially bound to a rostral cluster of glomeruli in the main olfactory bulb. This finding suggests the presence of a functional subset of primary projections to the main olfactory system. Our results therefore demonstrated a region-specific glycoconjugate expression in the olfactory bulb of C. ensicauda, which would be related to a functional segregation of the olfactory system., (© 2017 Blackwell Verlag GmbH.)

Vertebral morphology, development, and evolution have been investigated for many decades, especially in the recent evo-devo era. Nevertheless, comparative data on development and ossification modes within the major tetrapod groups are scarce and frequently suffer from the use of a simplistic approach, resulting in simplistic generalizations about the formation of tetrapod vertebrae. Here, we describe the development and ossification of trunk vertebrae in Triturus ivanbureschi (Salamandridae, Caudata) and compare the results with published data on other related taxa. In so doing, we focus on the modes of ossification and development of the centrum and neural arches by analysing three developmental stages defined by the degree of limb development: stages 47, 52, and 62 according to Glücksohn (1932). Our examination of histological sections through trunk vertebrae enabled us to identify three modes of ossification within single trunk vertebrae: (i) perichordal (direct ossification of the connective tissue surrounding the notochord); (ii) perichondrial (direct ossification of the perichondrium, consisting of cartilage-covering connective tissue), and (iii) endochondral (ossification within the preformed cartilage template). We also noted the presence of intravertebral or notochordal cartilage. Although our results indicate that this cartilage develops within the notochord surrounded by the continuous notochordal sheath, more detailed further studies could shed light on its origin and development., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Mounting evidence suggests that amphibians are globally and currently the most threatened group of vertebrates and different causes might be responsible for this phenomenon. Acidification of water bodies is a global environmental issue that has been proposed as a possible cause for amphibian populations decline. Indeed, it has been widely demonstrated that low pH may exert harmful effects on amphibians, either directly or by increasing the adverse effects of other stressors. Surprisingly only few studies documented the response of amphibian integument to acidic pH conditions and no data are available on the effects of a non-lethal level of pH onto the amphibian larval epidermis. The present study showed that acidic pH (4.5) condition has severe effects on the epidermis of the Italian newt (Lissotriton italicus, formerly Triturus italicus) inducing both morphological and functional alterations. The increase of mucus is the first evident effect of acid injury, followed by the flattening of the epithelium and the appearance of a keratinized shedding layer. The immunolabeling of cytokeratins substantially changes acquiring an adult-like pattern. Also aquaporin 3 and iNOS expression modify their distribution according to a change of the histological features of the epidermis. These results clearly indicate that a short-term exposure to a sub-lethal pH disrupts the epidermis morphology and function in L. italicus larvae. Since the skin exerts a prominent role in both respiration and osmoregulation, the described alterations may adversely affect the overall ionic balance, with a long chain of cascading effects significantly decreasing newts survival probabilities when environmental pH lowering occurs., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Tetrapod limbs are serially homologous structures that represent a particularly interesting model for studies on morphological integration, i.e. the tendency of developmental systems to produce correlated variation. In newts, limbs develop at an early larval stage and grow continuously, including after the habitat transition from water to land following metamorphosis. However, aquatic and terrestrial environments impose different constraints and locomotor modes that could affect patterns of morphological integration and evolvability. We hypothesize that this would be the case for alternative heterochronic morphs in newts, i.e. aquatic paedomorphs that keep gills at the adult stage and adult metamorphs that are able to disperse on land. To this end, we analyzed patterns and strengths of correlations between homologous skeletal elements of the fore- and hindlimbs as well as among skeletal elements within limbs in both phenotypes in the alpine newt, Ichthyosaura alpestris. Our results showed that metamorphs and paedomorphs had similar, general patterns of limb integration. Partial correlations between homologous limb elements and within limb elements were higher in paedomorphs when compared to metamorphs. A decrease in partial correlation between homologous limb elements in metamorphs is accompanied with a higher evolvability of the terrestrial morph. All these results indicate that environmental demands shaped the patterns of morphological integration of alpine newt limbs and that the observed diversity in correlation structure could be related to a qualitative difference in the modes of locomotion between the morphs., (© 2017 Wiley Periodicals, Inc.)

Salamanders use the hyobranchial apparatus and its associated musculature for tongue projection on land and for suction feeding in water. Hyobranchial apparatus composition and morphology vary across species, and different morphologies are better suited for feeding in aquatic versus terrestrial environments. We hypothesize that differences in hyobranchial morphology result in functional trade-offs in feeding performance. We predict that semi-aquatic and aquatic salamandrids with hyobranchial morphology suited for aquatic feeding will have lower performance, in terms of tongue-projection distance, velocity, acceleration and power, compared with terrestrial salamandrids when feeding in a terrestrial environment. We found that semi-aquatic and aquatic newts had lower velocity, acceleration and muscle-mass-specific power of tongue projection when compared with the terrestrial salamanders Chioglossa lusitanica and Salamandra salamandra The fully aquatic newt, Paramesotriton labiatus , has a robust, heavily mineralized hyobranchial apparatus and was unable to project its tongue during terrestrial feeding, and instead exhibited suction-feeding movements better suited for aquatic feeding. Conversely, terrestrial species have slender, cartilaginous hyobranchial apparatus and enlarged tongue pads that coincided with greater tongue-projection distance, velocity, acceleration and power. Chioglossa lusitanica exhibited extreme tongue-projection performance, similar to that seen in elastically projecting plethodontid salamanders; muscle-mass-specific power of tongue projection exceeded 2200 W kg -1 , more than 350 times that of the next highest performer, S salamandra , which reached 6.3 W kg -1 These findings reveal that two fully terrestrial salamandrids have morphological specializations that yield greater tongue-projection performance compared with species that naturally feed in both aquatic and terrestrial environments., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2017. Published by The Company of Biologists Ltd.)

Because reproductive isolation often evolves gradually, differentiating lineages may retain the potential for genetic exchange for prolonged periods, providing an opportunity to quantify and to understand the fundamental role of gene flow during speciation. Here we delimit evolutionary lineages, reconstruct the phylogeny and infer gene flow in newts of the Lissotriton vulgaris species complex based on 74 nuclear markers sampled from 127 localities. We demonstrate that distinct lineages along the speciation continuum in newts exchange nontrivial amounts of genes, affecting their evolutionary trajectories. By integrating a wide array of methods, we delimit nine evolutionary lineages and show that two principal factors have driven their genetic differentiation: time since the last common ancestor determining levels of shared ancestral polymorphism, and shifts in geographic distributions determining the extent of secondary contact. Post-divergence gene flow, indicative of evolutionary non-independence, has been most extensive in Central Europe, while four southern European lineages have acquired the population-genetic hallmarks of independent species (L. graecus, L. kosswigi, L. lantzi, L. schmidtleri). We obtained strong statistical support for widespread mtDNA introgression following secondary contact, previously suggested by discordance between mtDNA phylogeny and morphology. Our study reveals long-term evolutionary persistence of evolutionary lineages that may periodically exchange genes with one another: although some of these lineages may become extinct or fuse, others will acquire complete reproductive isolation and will carry signatures of this complex history in their genomes., (Copyright © 2017 Elsevier Inc. All rights reserved.)

New amphibian species have been constantly discovered throughout southern China, including from areas close to heavily populated cities that remain poorly surveyed for amphibian diversity. We describe a new species of the newt genus Paramesotriton from Fujian, a developed province on the southeastern coast of mainland China. The mitochondrial genealogy suggests that the new species is the sister taxon to Paramesotriton hongkongensis, separated by an uncorrected pairwise distances of 5.8% at the ND2 gene fragment analyzed. In addition to the genetic divergence, the new species can be readily differentiated from its congeners by having: a very rough skin; a continuous, orange, vertebral ridge; few warts on each side of the vertebral ridge; numerous small irregular orange-red or yellow spots on the chin, venter, underside of axillae, flanks, lateral side of the tail, base of limbs and cloaca; a small groove at the base of the vomerine tooth series; relatively long tail, relatively flat cloaca in females; normally developed eyes, and the absence of vestigial gills and gill filaments in adults.

Habitat fragmentation is one of the main drivers of global amphibian decline. Anthropogenic landscape elements can act as barriers, hindering the dispersal that is essential for maintaining gene flow between populations. Dispersal ability can be influenced by locomotor performance, which in turn can depend on morphological traits, such as hindlimb length (HLL) in amphibians. Here, we tested relationships between HLL and environmental variables--road types, forests and agricultural lands--among 35 sub-populations of palmate newts (Lissotriton helveticus) in southwestern France. We expected roads to select for short-legged newts due to a higher mortality of more mobile individuals (long-legged newts) when crossing roads. Accordingly, short-legged newts were found in the vicinity of roads, whereas long-legged newts were found closer to forests and in ponds close geographically to another water body. HLL in newts was hence influenced by habitat types in a heterogeneous landscape, and could therefore be used as an indicator of population isolation in a meta-population system., (© 2016 The Author(s).)

Despite recent descriptions of multiple new species of the genus Pachytriton (Salamandridae), species richness in this China-endemic newts genus likely remains underestimated. In this study, we describe a new species of Pachytriton from northeastern Guangxi and southern Hunan, southeastern China. Both molecular analyses and morphological characters reveal that the new species can be distinguished from its congeners. The mitochondrial gene tree identified the new lineage highly divergent (uncorrected p-distance > 5.8 % by mitochondrial gene) from currently recognized species and placed it as the sister species of P. xanthospilos and P. changi. Furthermore, a nuclear gene haplotype network revealed a unique haplotype in the new populations. Statistical species delimitation using Bayes factor strongly supported the evolutionary independence of the new species from the closely-related P. xanthospilos. Morphologically, the new species is characterized by a uniformly dark brown dorsum without bright orange dots or black spots; irregular orange blotches on the venter; tips of fingers and toes orange on the dorsal side; moderately developed webs on the side of digits; absence of costal grooves between the axilla and groin; and widely open vomerine tooth series.

Background: Many animals rely on their escape performance during predator encounters. Because of its dependence on body size and temperature, escape velocity is fully characterized by three measures, absolute value, size-corrected value, and its response to temperature (thermal sensitivity). The primary target of the selection imposed by predators is poorly understood. We examined predator (dragonfly larva)-imposed selection on prey (newt larvae) body size and characteristics of escape velocity using replicated and controlled predation experiments under seminatural conditions. Specifically, because these species experience a wide range of temperatures throughout their larval phases, we predict that larvae achieving high swimming velocities across temperatures will have a selective advantage over more thermally sensitive individuals., Results: Nonzero selection differentials indicated that predators selected for prey body size and both absolute and size-corrected maximum swimming velocity. Comparison of selection differentials with control confirmed selection only on body size, i.e., dragonfly larvae preferably preyed on small newt larvae. Maximum swimming velocity and its thermal sensitivity showed low group repeatability, which contributed to non-detectable selection on both characteristics of escape performance., Conclusions: In the newt-dragonfly larvae interaction, body size plays a more important role than maximum values and thermal sensitivity of swimming velocity during predator escape. This corroborates the general importance of body size in predator-prey interactions. The absence of an appropriate control in predation experiments may lead to potentially misleading conclusions about the primary target of predator-imposed selection. Insights from predation experiments contribute to our understanding of the link between performance and fitness, and further improve mechanistic models of predator-prey interactions and food web dynamics.

Mitochondrial DNA (mtDNA) sequence data are widely used to delimit species. However, owing to its strict maternal inheritance in most species, mtDNA tracks female dispersion and dispersal only. The accuracy of mtDNA-derived species delimitation is often not explicitly tested using other independent evidence, such as nuclear DNA (nDNA) data, morphological data, or ecological data. Because species are independent evolutionary lineages that can form testable hypotheses, we present a multi-evidence case study on species delimitation that combines statistical approaches with spatially explicit ecological analysis. Montane salamanders of the Pachytriton brevipes complex (Salamandridae) from southeastern China exhibit conservative morphology and variable color patterning that impede species diagnosis. Recent studies proposed splitting P. brevipes into four species based on deep mtDNA divergence but also found discordance between mtDNA and nDNA trees. In this study, we test evolutionary independence of these hypothesized species lineages using two coalescent-based Bayesian methods (Bayes factor and BP&P). Despite significant conflict between mtDNA gene tree and the species phylogeny, the results reinforce the inference of at least four species in the complex as opposed to the one species recognized for over 130 years. Correlative ecological niche modeling and statistical analysis of environmental data indicate that suitable habitats for each species are isolated by incompatible intervening lowland regions, so the likelihood of gene flow among species is very low, which means species lineages should maintain their evolutionary independence. We demonstrate that concordance among independent evidence confirms species status, which forms the basis for accurate assessment of regional biodiversity., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The salamandrid genus Tylototriton is poorly known in Laos, with one described species and unverified reports of two others. We undertook new fieldwork and obtained samples of Tylototriton at six localities across northern Laos during 2009-2013. Bayesian phylogenetic analysis of mitochondrial DNA, principal component analyses of 13 mensural characters, and qualitative morphological comparisons with samples from across the geographic range of Tylototriton were performed. Samples from Laos fell into four molecular and morphological groups, consisting of T. notialis, T. panhai, T. anguliceps, and a fourth lineage that is hypothesized here to be an undescribed species. Tylototriton podichthys sp. nov. is distinguished from its congeners by having distinct mitochondrial DNA haplotypes and in characteristics of the glandular skin on the head and body, shape of the rib nodules, and coloration of the body and limbs. This study expands the number of confirmed Tylototriton species in Laos from one to four, with the description of one species and extension of the ranges of T. panhai and T. anguliceps to Laos. An improved understanding of the geographic ranges of T. podichthys sp. nov. and T. anguliceps within Laos is needed.

Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. It is considered to be a suitable biomarker of the in utero balance of fetal sex hormones, which affect early development of individuaĺs behavioral and morphological characteristics. In recent decades, digit ratio attracted a great attention in biology and psychology. However, for unmasking the biological basis of the phenomenon, extensive studies on non-human animals are necessary. Despite it was hypothesized that digit ratio is well conserved in all Tetrapoda, and there exist studies on mammals, birds, and reptiles, there are only two such study on anuran amphibians. Therefore, the aim of this study is to investigate the 2D:4D in the most basal salamanders, Caudata. We have studied digit ratio in four species of newts: Triturus cristatus, Mesotriton alpestris, Lissotriton montandoni, and Lissotriton vulgaris, using museum collection. We used computerized measuring of each limbś photos. We have found out that, in M. alpestris, females 2D:4D of all four limbs were significantly larger than in males. In L. montandoni and L. vulgaris, only 2D:4D of rear limbs significantly differed, in females being larger. In T. cristatus, digit ratios of males and females did not statistically differ. Thus, the results confirmed our hypothesis that at least in M. alpestris, L. montandoni, and L. vulgaris, females seem to have larger 2D:4D comparing to males, the pattern known from most mammals and opposite to birds, reptiles and anuran amphibians., (© 2015 Wiley Periodicals, Inc.)

Disjunct geographic distribution of a species or a group of species is the product of long-term interaction between organisms and the environment. Filling the distributional gap by discovery of a new population or a species has significant biogeographic implications, because it suggests a much wider past distribution and provides evidence for the route of range expansion/contraction. The salamandrid genus Echinotriton (commonly known as spiny salamanders, spiny newts, or crocodile newts) has two species that are restricted to two widely separated areas, one in eastern Zhejiang province, China and the other in the Ryukyu Archipelago of Japan. It has been hypothesized that Echinotriton was once continuously distributed between the two areas through a historical land bridge that connected mainland China, Taiwan, and the archipelago. Finding fossils or relic populations along the postulated distribution are strong evidence for the hypothesis. Hundred-twenty-two years after the description of E. andersoni and eight-one years after that of E. chinhaiensis, we discover a third species of Echinotriton in southern China, which fills the distributional gap of the former two species. Species status of the new species is confirmed through molecular phylogenetic analysis and morphological comparison. Mitochondrial DNA indicates that the new species is sister to E. chinhaiensis, while nuclear DNA does not support this relationship. The new species has a very large quadrate projection, a single line of lateral warts pierced by distal rib extremities, normally developed 5th toes, and conical skin tubercles. Our discovery supports the hypothesis that there was a continuous distribution of Echinotriton from eastern coastal China to the Ryukyu Archipelago. We suggest that other species of this genus may also be found in Taiwan. Due to the rarity of this new species, we urge all hobbyists to refrain themselves from collecting this salamander or leaking locality information if encountered, and boycott any trading.

The question of why females evaluate more than one sexual trait to choose their mates has received increasing attention in recent years. Here, we investigated the information-content of both morphological and behavioural sexual traits that have been identified as predictors of male reproductive success in the palmate newt, Lissotriton helveticus. We examined the co-variation of multiple traits with one aspect of male quality, the male body condition, using both a correlative study and an experimental diet restriction. We found that the development of the three morphological sexual traits (filament length, hind-foot-web size, and crest size) was positively inter-correlated, and was correlated to body condition. In contrast, courtship activity, an important indicator for male reproductive success, was uncorrelated to male body condition. Our results suggest that females likely obtain redundant information on male condition when evaluating filament length, hind-foot-web size and crest size during mate choice. Contrary to our expectations, display activity was not a reliable indicator of male condition, leaving the information-content of this trait unraveled. Our results further suggest that complex, multiple traits may evolve because redundant message, unreliable signals and, possibly, multiple messages can coexist., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Abundant new ichthyosaur material has recently been documented in the Slottsmøya Member of the Agardhfjellet Formation from the Svalbard archipelago of Norway. Here we describe a partial skeleton of a new taxon, Janusaurus lundi, that includes much of the skull and representative portions of the postcranium. The new taxon is diagnosed by a suite of cranial character states including a very gracile stapedial shaft, the presence of a dorsal process on the prearticular and autapomorphic postcranial features such as the presence of an interclavicular trough and a conspicuous anterodorsal process of the ilium. The peculiar morphology of the ilia indicates a previously unrecognized degree of morphological variation in the pelvic girdle of ophthalmosaurids. We also present a large species level phylogenetic analysis of ophthalmosaurids including new and undescribed ichthyosaur material from the Upper Jurassic of Svalbard. Our results recover all Svalbard taxa in a single unresolved polytomy nested within Ophthalmosaurinae, which considerably increases the taxonomic composition of this clade. The paleobiogeographical implications of this result suggest the presence of a single clade of Boreal ophthalmosaurid ichthyosaurs that existed during the latest Jurassic, a pattern also reflected in the high degree of endemicity among some Boreal invertebrates, particularly ammonoids. Recent and ongoing descriptions of marine reptiles from the Slottsmøya Member Lagerstätte provide important new data to test hypotheses of marine amniote faunal turnover at the Jurassic-Cretaceous boundary.

Background: Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic-Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and 'greensands' deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation) offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early-Late Cretaceous boundary., Methodology/principal Findings: To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France); a revised taxonomic scheme is proposed. We recognize the following taxa in the 'greensands': the platypterygiines 'Platypterygius' sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa., Conclusion/significance: Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian-early Cenomanian ichthyosaurs. This provides a whole new context to investigate the extinction of these successful marine reptiles, at the end of the Cenomanian.

In this paper, an observation on the toe pad of a newt was carried out. It was found that the pad surface is covered with an array of polygonal cells separated by channels, similar to those of a tree frog's pad. With this micro-structure, a newt can move on wet and smooth surfaces without slipping. Inspired by the surface structure of newt toe pads, elastic micro-patterned surfaces were fabricated to understand the function of such micro-structures in friction systems. The tribological performance of the patterned surfaces was evaluated using a tribometer. Different tribological performances between micro-dimple and -pillar patterned surfaces were observed. The area density (r) of the micro-pattern is crucial for controlling the friction of the elastic surface. Distinguished from unpatterned and micro-dimple patterned surfaces, the pillar patterned surface with high area density can remain high friction at high sliding speed. It could be one of the reasons of such polygonal structures on newt's toe pads.

Three morphological groups are found in a salamandrid newt Tylototriton shanjing from Thailand. We describe two of them as new species, one from northern and the other from northeastern Thailand, based on molecular and morphological data, however we could not make a taxonomic decision on the remaining one group because of the lack of voucher specimens and sufficient genetic data. The northern species differs morphologically from all known congeners by having the combination of orange to reddish brown markings, narrow and sharply protruding dorsolateral bony ridges on head, weakly segmented vertebral ridge, and long and high tail. The northeastern species is characterized by having the combination of yellow, orange, or reddish brown markings, wide and moderately protruding dorsolateral bony ridges on head, smooth vertebral ridge, black limbs, and black tail except for edges. Validity of taxonomic subdivision of the genus Tylototriton is discussed.

This study presents the first light microscopy-based description of the cloacal anatomy of male Carpathian newts (Lissotriton montandoni). This European newt species hybridizes with its sister species, the smooth newt (L. vulgaris), despite a high level of prezygotic isolation. The goal of the study was to ascertain possible anatomical differences in cloacal anatomy, especially pheromone and spermatophore producing glands, which might potentially affect reproductive isolation between L. montandoni and L. vulgaris. The cloaca of L. montandoni males consists of the cloacal tube, cloacal chamber, pseudopenis, and aggregations of cloacal glands. Four main types of cloacal glands were recognized. Pheromone-producing dorsal glands are of two types due to differences in their secretory epithelium: cuboidal and high prismatic. The remaining glands: ventral, pelvic, and Kingsbury's glands, are most likely involved in the synthesis of spermatophore components. Two distinct groups of ventral glands were identified: posterior and anterior ventral glands. In comparison with L. vulgaris, no evident differences were found that could potentially affect courtship pheromone synthesis by dorsal glands or the base and the cap of the spermatophore produced by the remaining cloacal glands.

During the evolutionary transition from fish to tetrapods, a shift from uni- to bidirectional suction feeding systems followed a reduction in the gill apparatus. Such a shift can still be observed during metamorphosis of salamanders, although many adult salamanders retain their aquatic lifestyle and feed by high-performance suction. Unfortunately, little is known about the interplay between jaws and hyobranchial motions to generate bidirectional suction flows. Here, we study the cranial morphology, as well as kinematic and hydrodynamic aspects related to prey capture in the Chinese giant salamander (Andrias davidianus). Compared with fish and previously studied amphibians, A. davidianus uses an alternative suction mechanism that mainly relies on accelerating water by separating the 'plates' formed by the long and broad upper and lower jaw surfaces. Computational fluid dynamics simulations, based on three-dimensional morphology and kinematical data from high-speed videos, indicate that the viscerocranial elements mainly serve to accommodate the water that was given a sufficient anterior-to-posterior impulse beforehand by powerful jaw separation. We hypothesize that this modified way of generating suction is primitive for salamanders, and that this behaviour could have played an important role in the evolution of terrestrial life in vertebrates by releasing mechanical constraints on the hyobranchial system.

The function and/or morphological features of the vomeronasal olfactory system remain unclear in aquatic animals, although the system appeared first in urodeles based on phylogenic data. We examined the lectin binding patterns in the olfactory bulb of a semi-aquatic urodele, the Japanese red-bellied newt, Cynops pyrrhogaster, using 22 different lectins. Eleven of the lectins showed specific binding to the nerve fibres and glomeruli in the olfactory bulb. Among these, Wheat germ agglutinin, pokeweed and peanut agglutinin preferentially bound the main olfactory bulb, reflecting variation in the expression of glycoconjugates between the main and accessory olfactory bulbs. By contrast, the types of lectins bound to the Cynops olfactory bulb were considerably different from those reported in other urodele families. These results suggest a histochemical distinction between the main and accessory olfactory bulbs, and that glycoconjugate expression may differ significantly among urodele families., (© 2011 Blackwell Verlag GmbH.)

Numerous alpine newt (Ichthyosaura alpestris) populations from the Balkans, representing all the previously established phylogeographic lineages, were studied for variations in various morphological characteristics (body size and shape, skull qualitative traits and number of trunk vertebrae). Here, we present a decoupling of morphological and mtDNA phylogeographic substructuring in the alpine newt on the Balkan Peninsula. In sharp contrast to other European newts (Triturus spp., Lissotriton spp.), the vast majority of morphological variation in the alpine newt is concentrated at the population level indicating an in situ morphological diversification. We found that the rate of morphological change is similar to the rate of mtDNA change. We hypothesize that the alpine newts are characterized by non-adaptive morphological evolution., (Copyright © 2011 Académie des sciences. Published by Elsevier SAS. All rights reserved.)

The dorsal crest of newts (Salamandridae) is a novel, phenotypically plastic, sexually selected trait that may evolve in association with complex courtship behaviours. We estimated a near-comprehensive, time-calibrated phylogeny for salamandrids and analysed the evolution of their crests and display behaviour. Different models give conflicting reconstructions for crest evolution, showing that likelihood can estimate incorrect ancestral states with strong statistical support. The best-fitting model suggests that crests evolved once and were lost repeatedly, supporting the hypothesis that sexually selected traits may be frequently lost. We demonstrate the correlated evolution of crests and courtship behaviour and show that species with larger numbers of crest-related traits have larger repertoires of behaviours. We also show that phenotypically plastic morphological traits can be maintained over long macroevolutionary timescales (∼25-48 Myr). Finally, we use salamandrids to address how novel structures may arise, and support a model involving the expansion and subdivision of pre-existing structures., (© 2011 The Authors. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.)

In this article, we explore the possible influences of the developmental and functional relationships between skeletal elements on the pattern of morphological integration in the adult skull of the alpine newt. Like many tailed amphibians, the alpine newt has a biphasic life cycle, which implies the possibility that two distinct sets of constraints on development and function of the cranial skeleton may act at different times. We study how trait covariation, resulting from processes early in development, affects patterns of covariation at the adult stage. We test whether the observed patterns of integration are consistent with those predicted from three a priori hypothesized sources of integration: developmental timing, hormonally mediated growth/remodeling during metamorphosis, and developmental and functional relationships. The analyses of the covariation among the landmarks in the dorsal and ventral alpine newt craniums yield somewhat contrasting results. Our results do not indicate a clear correspondence between the observed variations in the skull shape and any of the three proposed hypotheses. No traceable reflection of hypothesized developmental relationships in the pattern of morphological integration/modularity in the adult skull indicate that covariation structure is continually restructured by overlaying variation introduced through developmental and environmental factors at different stages of development. This finding supports the recently elaborated palimpsest view of morphological integration. Also, our results indicate that the allometry-free shape data have an even higher level of morphological integration than the data that contain the allometric component of the shape variation., (Copyright © 2010 Wiley-Liss, Inc., A Wiley Company.)

Lens regeneration among vertebrates is basically restricted to some amphibians. The most notable cases are the ones that occur in premetamorphic frogs and in adult newts. Frogs and newts regenerate their lens in very different ways. In frogs the lens is regenerated by transdifferentiation of the cornea and is limited only to a time before metamorphosis. On the other hand, regeneration in newts is mediated by transdifferentiation of the pigment epithelial cells of the dorsal iris and is possible in adult animals as well. Thus, the study of both systems could provide important information about the process. Molecular tools have been developed in frogs and recently also in newts. Thus, the process has been studied at the molecular and cellular levels. A synthesis describing both systems was long due. In this review we describe the process in both Xenopus and the newt. The known molecular mechanisms are described and compared., (Copyright © 2010. Published by Elsevier Ltd.)

Corticotropin-releasing factor (CRF) is a peptide well known for its role in coordinating various neuroendocrine, autonomic, and behavioral components of the vertebrate stress response, including rapid enhancement of locomotor activity. Although CRF's locomotor enhancing properties are well documented, the neuronal mechanisms and specific target neurons that underlie the peptide's effect on locomotor behavior remain poorly understood. In the present study, we describe the synthesis and functional characteristics of a CRF rhodamine analogue TAMRA-X conjugate mixture (CRF-TAMRA 1), to be used for tracking this peptide's internalization into target neurons in the brainstem of an amphibian, the roughskin newt (Taricha granulosa). CRF-TAMRA 1 conjugate administration into the lateral cerebral ventricle resulted in a rapid, endosomal-like internalization of fluorescence into brainstem medullary neurons. In addition, central CRF-TAMRA 1 administration produced neurobehavioral effects comparable to the native peptide, effects that were blocked by pre-treatment with the CRF receptor antagonist, alpha-helical CRF. Taken together, our results show the efficacy of CRF-TAMRA 1 as a novel tool for tracking CRF internalization into targets neurons in vivo and ultimately, aiding in elucidating the neuronal mechanisms and circuitry underlying CRF's influence on behavioral and physiological responses to stress.

In this study, we present data indicating that mammalian stem cell pluripotency-inducing factors are expressed during lens and limb regeneration in newts. The apparent expression even in intact tissues and the ensued regulation during regeneration raises the possibility that these factors might regulate tissue-specific reprogramming and regeneration. Furthermore, these factors should enable us to understand the similarities and differences between animal regeneration in the newt and stem cell strategies in mammals. Developmental Dynamics 238:1613-1616, 2009. (c) 2009 Wiley-Liss, Inc.

Reproductive character displacement is commonly described as larger phenotypic differences between species living in sympatry rather than in allopatry. We investigated this phenomenon on two amphibians found in their contact zone where syntopic and allotopic sites alternate. To test the effect of syntopy with Lissotriton vulgaris on the Lissotriton helveticus phenotype, we studied the morphology of adult males and females while controlling for environmental factors (i.e. land use and flood risk). Using linear mixed-effects models, we found that females of L. helveticus expressed a deeper tail when in the presence of the other species, a pattern consistent with reproductive character displacement. This pattern has been rarely observed in Amphibians. It suggests that male newts incur large mating costs when selecting heterospecific partners. Our study also emphasizes that the evolution of mate recognition systems could occur at a microgeographical scale within a sympatric area.

Hormonal involvement in the performance of reproductive behavior of the red-bellied newt Cynops pyrrhogaster is described. The sexually developed male newt is likely to recognize the sexually responsive female newt by a yet unidentified substance released from the oviduct, secretion of this substance being stimulated by prolactin (PRL) and estrogen. At the initial stage of courtship behavior, the male newt vibrates his tail vigorously in front of the female partner. This action is elicited by PRL and androgen and is enhanced by another hormonal factor, arginine vasotocin (AVT). Both PRL and AVT were shown to act centrally to elicit this behavior. A recently discovered neurosteroid, 7alpha-hydroxypregnenolone, was also revealed to be an important factor for eliciting tail vibrating behavior. During courtship, the male newt emits a decapeptide pheromone that attracts the female partner. The synthesis of this attractant by the abdominal gland is promoted by PRL and androgen and its release from the cloaca is elicited by AVT. The responsiveness to the pheromone of the vomeronasal epithelial cells of the female newt is enhanced by PRL and estrogen. Toward the final stage of courtship, the male newts deposits spermatophores, which are picked up through the cloacal orifice of the female newt. AVT induces the discharge of spermatophores from the cloaca. Thus, PRL, AVT, androgen, estrogen, and the neurosteroid, 7alpha-hydroxypregnenolone, are considered to be important factors for the performance of reproductive behavior in the red-bellied newt.

The adult newt retinal regeneration is an ideal model for studying retinal regeneration by transdifferentiation of the retinal pigment epithelium (RPE) cells. Accumulated evidence suggests that the RNA-binding protein Musashi-1 (Msi1) is expressed in mature photoreceptors and RPE cells as well as in retinal stem/progenitor cells, being essential for vision. We have been investigating whether Msi1 is also essential for retinal regeneration. In the last paper [K. Susaki, J. Kaneko, Y. Yamano, K. Nakamura, W. Inami, T. Yoshikawa, Y. Ozawa, S. Shibata, O. Matsuzaki, H. Okano, C. Chiba, Musashi-1, an RNA-binding protein, is indispensable for survival of photoreceptors. Exp. Eye Res. (in press)], we showed that the expression profiles of Msi1 transcripts and protein isoforms change during retinal regeneration. In the current report, we show by immunohistochemistry that Msi1 is expressed in transdifferentiating cells or cells of regenerating retinal tissues. Upon retinectomy, Msi1 protein, which is expressed in the nuclei of intact (stage E-0) RPE cells, changed its subcellular localization, being expressed in both the nucleus and cytoplasm of the RPE-derived stem-like cells at stage E-1. As the retinal rudiment/regenerating retina (rR) and renewing RPE (rRPE) are specified from the stem-like cell population (stage E-2), Msi1 expression was maintained or up-regulated in the rR, while down-regulated in the rRPE. During further retinal regeneration, Msi1 expression was decreased in association with cell differentiation, except for photoreceptors and RPE cells whose Msi1 expression increased as they differentiate. Thus, Msi1 is likely to be regulated at various cellular events during retinal regeneration, implying that Msi1 may have multi-functions in retinal regeneration. All together, it is probable that Msi1 is one of the essential factors that need to be regulated in retinal regeneration.

Submicron local cAMP elevation was used to map the distribution of transduction channels in single olfactory cilia. After the fine fluorescent visualization of the cilium with the laser-scanning confocal microscope, the intraciliary cAMP was jumped locally with the laser beam that photolyzes cytoplasmic caged compounds. Simultaneously, cells' responses were obtained with the whole-cell patch clamp. Responses were observed anywhere within the cilia, showing the broad distribution of transduction channels. For odor detection, such distribution would be useful for expanding the available responding area to increase the quantum efficiency. Also, the stimulus onto only 1 microm region induced >100 pA response operated by >700-2300 channels, although only 1 pA is sufficient for olfactory cells to generate action potentials. The large local response indicates a presence of strong amplification achieved with a high-density distribution of the transduction channels for the local ciliary excitation.

MicroRNAs are known to regulate the expression of many mRNAs by binding to complementary target sequences at the 3'UTRs. Because of such properties, miRNAs may regulate tissue-specific mRNAs as a cell undergoes transdifferentiation during regeneration. We have tested this hypothesis during lens and hair cell regeneration in newts using microarray analysis. We found that distinct sets of miRNAs are associated with lens and hair cell regeneration. Members of the let-7 family are expressed in both events and they are regulated in a similar fashion. All the let-7 members are down regulated during the initiation of regeneration, which is characterized by dedifferentiation of terminally differentiated cells. This is the first report to correlate expression of miRNAs as novel regulators of vertebrate regeneration, alluding to a novel mechanism whereby transdifferentiation occurs.

Most nonmammalian species replace their teeth continuously (so-called polyphyodonty), which allows morphological and structural modifications to occur during ontogeny. We have chosen Pleurodeles waltl, a salamander easy to rear in the laboratory, as a model species to establish the morphological foundations necessary for future molecular approaches aiming to understand not only molecular processes involved in tooth development and replacement, but also their changes, notably during metamorphosis, that might usefully inform studies of modifications of tooth morphology during evolution. In order to determine when (in which developmental stage) and how (progressively or suddenly) tooth modifications take place during ontogeny, we concentrated our observations on a single tooth family, located at position I, closest to the symphysis on the left lower jaw. We monitored the development and replacement of the six first teeth in a large growth series ranging from 10-day-old embryos (tooth I1) to adult specimens (tooth I6), using light (LM), scanning (SEM), and transmission electron (TEM) microscopy. A timetable of the developmental and functional period is provided for the six teeth, and tooth development is compared in larvae and young adults. In P. waltl the first functional tooth is not replaced when the second generation tooth forms, in contrast to what occurs for the later generation teeth, leading to the presence of two functional teeth in a single position during the first 2 months of life. Larval tooth I1 shows dramatically different features when compared to adult tooth I6: a dividing zone has appeared between the dentin cone and the pedicel; the pulp cavity has enlarged, allowing accommodation of large blood vessels; the odontoblasts are well organized along the dentin surface; tubules have appeared in the dentin; and teeth have become bicuspidate. Most of these modifications take place progressively from one tooth generation to the next, but the change from monocuspid to bicuspid tooth occurs during the tooth I3 to tooth I4 transition at metamorphosis., ((c) 2006 Wiley-Liss, Inc.)

Several studies have reported climate-associated changes in phenotypically plastic traits of amphibians, yet it remains unknown whether amphibians can manifest an evolutionary response to global climate change at the rate and magnitude that it is occurring. To assess this issue, we examined temporal change in the morphology of the red-backed salamander (Plethodon cinereus), a small, abundant woodland salamander distributed widely in eastern North America with two distinct morphotypes: striped individuals associated with cooler microclimates and unstriped individuals associated with warmer microclimates. We compiled morph frequencies for 50,960 individual salamanders from 558 sites as recorded in the published literature and in unpublished field notes of herpetologists between 1908 and 2004. We observed that striping probability increased with increasing latitude, longitude, and elevation and decreased (from 80% to 74% range wide) with time. The combined forces of regional climate warming and, particularly, forest disturbance have evidently been sufficient to cause morphological evolution in this amphibian over the last century.

Salamanders are generally agreed to represent the primitive tetrapod body plan, as well as a postural analog for early tetrapods. Dissection and description of the muscles of the forelimb, trunk, and hindlimb of the California newt, Taricha torosa, were undertaken to provide baseline data on the locomotor structures in this species. Hypaxial trunk muscles are similar to those of other vertebrates. As in other salamanders, limb muscles show a simple parallel-fibered architecture and often span multiple joints. Several differences in limb musculature were also noted. The extensor iliotibialis muscle possesses a single head in T. torosa, rather than the two heads common in larger salamander species. The ischioflexorius muscle, while divided into proximal and distal sections, is not distinct from the puboischiotibialis in its proximal portion. The femorofibularis is enlarged in this species; it is suggested that the femorofibularis and ischioflexorius muscles may be functionally analogous systems. Forelimb and hindlimb musculature show similar morphological patterns, particularly in distal limb segments, which may provide insight into the primitive arrangement of tetrapod limb muscles.

Type I cannabinoid receptor (CB1) is a G-protein coupled receptor with a widespread distribution in the central nervous system in mammals. In a urodele amphibian, the rough-skinned newt (Taricha granulosa), recent evidence indicates that endogenous cannabinoids (endocannabinoids) mediate behavioral responses to acute stress and electrophysiological responses to corticosterone. To identify possible sites of action for endocannabinoids, in situ hybridization using a gene and species specific cRNA probe was used to label CB1 mRNA in brains of male T. granulosa. Labeling of CB1 mRNA in the telencephalon was observed in the olfactory bulb and all areas of the pallium, as well as the bed nucleus of the stria terminalis and nucleus amygdalae dorsolateralis. The labeling of CB1 mRNA was also found in regions of the preoptic area, thalamus, midbrain tegmentum and tectum, cerebellum, and the stratum griseum of the hindbrain. A notable difference in CB1 labeling between this amphibian and mammals is the abundance of labeling in areas associated with olfaction (anterior olfactory nuclei, nucleus amygdalae dorsolateralis, and lateral pallium), which hints that endocannabinoids might modulate responses to odors as well as pheromones. This widespread distribution of CB1 labeling, particularly in sensory and motor control centers, fits with prior results showing that endocannabinoids modulate sensorimotor processing and behavioral output in this species. The distribution of CB1 in the brain of T. granulosa was in many of the same sites previously observed in the brain of the anuran amphibian, Xenopus laevis, as well as those of different species of mammals, suggesting that endocannabinoid signaling pathways are conserved., (2006 S. Karger AG, Basel)

Arginine8 vasotocin (AVT), a neurohypophyseal peptide in nonmammalian vertebrates, plays a key role in the regulation of social behaviors related to reproduction. In male roughskin newts (Taricha granulosa), AVT is an important facilitator of several reproductive behaviors, including courtship clasping of females. Although AVT is known to act in certain brain regions and AVT receptors have been localized to some extent, specific target neurons for this peptide have not been identified in any species. Internalization of a receptor-specific conjugate of AVT and the fluorescent dye Oregon green was used to identify AVT target cells in the medulla of male roughskin newts. Medullary neurons are of interest because they appear to mediate facilitation of clasping by AVT. Direct application of AVT-Oregon green to the fourth ventricular surface of the medulla in vivo resulted in conjugate internalization by a widespread population of medullary neurons, particularly in the medial reticular formation and nuclei of cranial nerves V, VII, VIII, IX, and X. Some fourth-ventricle ependymal cells were also labeled. Reticulospinal neurons, which play an important role in clasping, were identified by retrograde labeling with tetramethylrhodamine dextran amine. AVT-Oregon green was internalized by 72% of these neurons. These results show that AVT can directly affect a very large and diverse medullary neuronal population, which may underlie the peptide's role in multiple neuroendocrinological processes, including autonomic and behavioral regulation. Selectivity of the AVT action may arise through interactions between AVT and steroids such as corticosterone., (2005 Wiley-Liss, Inc.)

The newts Triturus vulgaris and Triturus montandoni are sister species that exhibit contrasting levels of intraspecific morphological variation. Triturus vulgaris has a broad Eurasiatic distribution encompassing both formerly glaciated and unglaciated areas and shows substantial morphological differentiation in the southern part of its range, while T. montandoni, confined to the Carpathians, is morphologically uniform. We analysed sequence variation of two mtDNA fragments of the total length of c. 1850 bp in 285 individuals of both species collected from 103 localities. Phylogenetic analysis of 200 unique haplotypes defined 12 major clades, their age estimated at c. 4.5-1.0 million years (Myr). Most of the older clades were found in the southern part of the range, and also in central Europe, mainly in Romania. The distribution of mtDNA clades points to the existence of several glacial refugia, located in the Caucasus region, Anatolia, the Balkan Peninsula, Italy, and more to the north in central Europe. The concordance between mtDNA based phylogeny and the distribution of T. vulgaris subspecies was weak. Triturus montandoni haplotypes did not form a monophyletic group. Instead they were found in six clades, in five of them mixed with T. vulgaris haplotypes, most likely as a result of past or ongoing hybridization and multiple introgression of mtDNA from T. vulgaris to T. montandoni. Patterns of sequence variation within clades suggested long-term demographic stability in the southern groups, moderate and relatively old demographic growth in the populations inhabiting central Europe, and high growth in some of the groups that colonized northern parts of Europe after the last glacial maximum.

To investigate the distribution of serotonin-positive neuroepithelial endocrine (NEE) cells in the respiratory tract of the red-bellied newt Cynops pyrrhogaster, serial sections of the respiratory tract were stained using immunohistochemical methods for serotonin, a periodic acid-Schiff method and hematoxylin-eosin staining. The respiratory tract of the red-bellied newt consisted of a tubular laryngotrachea and two pulmonary sacs. Serotonin-positive solitary NEE cells were distributed widely throughout the ciliomucous epithelium of the laryngotrachea. The innervated clusters of NEE cells, termed neuroepithelial bodies, were rarely found in the caudal portion of the laryngotrachea. The density of NEE cells was high in the middle portion of the laryngotrachea, particularly in the region surrounded by a striated laryngeal sphincter, and the densities were low cranially towards the aditus laryngis and caudally in the pulmonary sacs, the epithelium of which consisted of both ciliomucous epithelial cells and non-ciliated respiratory epithelial cells or pneumocytes. The NEE cells were not observed in the vicinity of non-ciliated respiratory epithelial cells. The morphology and distribution of serotonin-positive NEE cells in the respiratory tract of the red-bellied newt were similar to those described in mammals, including humans. The close localization of NEE cells with ciliary and mucous cells and the distribution of NEE cells in the laryngotrachea suggest that NEE cells play important roles in the defense and repair of the ciliomucous epithelium, such as increasing mucous secretion, ciliary beat frequency and the proliferation of epithelial cells.

Complete retinal regeneration in adult animals occurs only in certain urodele amphibians, in which the retinal pigmented epithelial cells (RPE) undergo transdifferentiation to produce all cell types constituting the neural retina. A similar mechanism also appears to be involved in retinal regeneration in the embryonic stage of some other species, but the nature of this mechanism has not yet been elucidated. The organ culture model of retinal regeneration is a useful experimental system and we previously reported RPE transdifferentiation of the newt under this condition. Here, we show that cultured RPE cells proliferate and differentiate into neurons when cultured with the choroid attached to the RPE, but they did not exhibit any morphological changes when cultured alone following removal of the choroid. This finding indicates that the tissue interactions between the RPE and the choroid are essential for the former to proliferate. This tissue interaction appears to be mediated by diffusible factors, because the choroid could affect RPE cells even when the two tissues were separated by a membrane filter. RPE transdifferentiation under the organotypic culture condition was abolished by a MEK (ERK kinase) inhibitor, U0126, but was partially suppressed by an FGF receptor inhibitor, SU5402, suggesting that FGF signaling pathway has a central role in the transdifferentiation. While IGF-1 alone had no effect on isolated RPE, combination of FGF-2 and IGF-1 stimulated RPE cell transdifferentiation similar to the results obtained in organ-cultured RPE and choroid. RT-PCR revealed that gene expression of both FGF-2 and IGF-1 is up-regulated following removal of the retina. Thus, we show for the first time that the choroid plays an essential role in newt retinal regeneration, opening a new avenue for understanding the molecular mechanisms underlying retinal regeneration.