Search results for "Amphibia"
showing 10 items of 71 documents
Is triploidy indisputably determinable in hybridogenetic hybrids by planimetric analyses of erythrocytes?
2008
The size of amphibian erythrocytes is positively correlated to their DNA content. Therefore, planimetry of erythrocytes has long been used to determine ploidy levels in amphibians. In Rana esculenta. a hybrid originating from Rana ridibunda x Rana lessonae natural crosses, planimetric determination of erythrocyte size is used to distinguish diploid and triploid specimen. In the present study we performed planimetric analyses on the hybrid Rana grafi, comprising a second hybridogenetic system with its parental species Rana ridibunda and Rana perezi in southern parts of France. We found size differences of diploid and triploid erythrocytes to range between 26 and 33% in studies on adult R. es…
Evolutionary History and Functional Characterization of the Amphibian Xenosensor CAR
2011
AbstractThe xenosensing constitutive androstane receptor (CAR) is widely considered to have arisen in early mammals via duplication of the pregnane X receptor (PXR). We report that CAR emerged together with PXR and the vitamin D receptor from an ancestral NR1I gene already in early vertebrates, as a result of whole-genome duplications. CAR genes were subsequently lost from the fish lineage, but they are conserved in all taxa of land vertebrates. This contrasts with PXR, which is found in most fish species, whereas it is lost from Sauropsida (reptiles and birds) and plays a role unrelated to xenosensing in Xenopus. This role is fulfilled in Xenopus by CAR, which exhibits low basal activity a…
Phylogeography of Ptychadena mascareniensis suggests transoceanic dispersal in a widespread African-Malagasy frog lineage
2004
Aim The Mascarene ridged frog, Ptychadena mascareniensis, is the only African amphibian species thought to occur on Madagascar and on the Seychelles and also Mascarene islands. We explored its phylogenetic relationships and intraspecific genetic differentiation to contribute to the understanding of transoceanic dispersal in amphibians. Methods Fragments of the mitochondrial 16S rRNA gene were sequenced from specimens collected over most of the distribution area of P. mascareniensis, including populations from Madagascar, Mascarenes and Seychelles. Results We identified five deeply divergent clades having pairwise divergences >5%, which probably all represent cryptic species in a P. mascaren…
The earliest tupilakosaurid amphibian with diplospondylous vertebrae from the Late Permian of southern France
2007
5 pages; International audience; A well-preserved vertebral column from the Late Permian of Southern France (Lopingian, La Lieude Formation, Lodève Basin) is described. It is composed of diplospondylous vertebrae and is most comparable with the temnospondyl Tupilakosaurus previously known from the Early Triassic of Greenland and Russia. This new specimen therefore represents the earliest occurrence of a diplospondylous tupilakosaur, and extends the geographic range of the group to Western Europe. It is an aquatic temnospondyl that used the anguilliform undulatory mode of swimming.
Is the painted frog Discoglossus pictus a declining species in Italy? On the reliability of a distributional atlas approach
2013
The conservation status of amphibians is often assessed using public databases because of a lack of up-to-date field data. However, it is crucial that this kind of data is used carefully, evaluating the reliability and the consistency of the information. In Italy, the conservation status of the painted frog, Discoglossus pictus, was recently assessed using public databases, and the outcome highlighted a worrying situation for the species. We analyzed the reliability of these conclusions and reassessed the status of the painted frog, taking into account its insular distribution and new data of species occurrence. Our results contrast with the previous analysis and show how an incautious use …
Amphibians of the Kayan Mentarang National Park (East Kalimantan, Indonesia): estimating overall and local species richness
2004
On the basis of surveys since 1997 and an intensive survey at the World Wildlife Fund field station at Lalut Birai in 2001, we assessed the importance of the Kayan Mentarang National Park in East Kalimantan for the conservation of Borneo's amphibian fauna. Sixty-five frog species and one Caecilian species are currently known to occur in this region. We report their occurrence in 16 subareas. Most of the species were recorded at Upper Bahau (41) and at the Lalut Birai field station (33). Based on the results of opportunistic searches and transect censuses at Lalut Birai, we argue that the amphibian diversity of the national park is still greatly underestimated.
The large invasive population of Xenopus laevis in Sicily, Italy
2008
AbstractThe worldwide spread of invasive species is considered to be one of the main causes of global amphibian declines and the loss of biodiversity in general. The African Clawed Frog, Xenopus laevis, shows a strong ability to establish populations and invade various geographic regions. In 2004 X. laevis was found in Sicily for the first time. The Sicilian population is probably the largest in Europe with a range of about 225 km2 in an area characterized by numerous agricultural ponds. This high density of ponds has potentially facilitated the dispersal of X. laevis. The frogs can move far from rivers or watercourses by utilizing the ponds as suitable "islands". The analysis of their diet…
Can the introduction of Xenopus laevis affect native amphibian populations? Reduction of reproductive occurrence in presence of the invasive species
2010
Biological invasions are regarded as a form of global change and potential cause of biodiversity loss. Xenopus laevis is an anuran amphibian native to sub-Saharan Africa with strong invasive capacity, especially in geographic regions with a Mediterranean climate. In spite of the worldwide diffusion of X. laevis, the effective impact on local ecosystems and native amphibian populations is poorly quantified. A large population of X. laevis occurs in Sicily and our main aim of this work was to assess the consequences of introduction of this alien species on local amphibian populations. In this study we compare the occurrence of reproduction of native amphibians in ponds with and without X. lae…
Catastrophic Population Declines and Extinctions in Neotropical Harlequin Frogs (Bufonidae: Atelopus)1
2005
We surveyed the population status of the Neotropical toad genus Atelopus, and document recent catastrophic declines that are more severe than previously reported for any amphibian genus. Of 113 species that have been described or are candidates for description, data indicate that in 42 species, population sizes have been reduced by at least half and only ten species have stable populations. The status of the remaining taxa is unknown. At least 30 species have been missing from all known localities for at least 8 yr and are feared extinct. Most of these species were last seen between 1984 and 1996. All species restricted to elevations of above 1000 m have declined and 75 percent have disappe…