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At least 73 records · Page 4Linked to original sources
PubMed1994

Chromosomal variation in the northwestern American newts of the genus Taricha (Caudata: Salamandridae).

Chromosomal variation was analysed in 22 populations of newts of the salmandrid genus Taricha of western North America, and compared with that of the eastern North American newts of the genus Notophthalmus. The karyotypes of the species Taricha and Notophthalmus were very similar. However, there was considerable variation in the distribution patterns of heterochromatins (revealed by C-banding) and in the sites of the nucleolar organizing region (NOR) (revealed by fluorochrome chromomycin A3 banding) within and between species of these two genera. Chromosomal variation patterns were interpreted in relation to a phylogenetic hypothesis derived from data on mitochondrial DNA sequences and allozyme variation. This study suggests that the pattern distributions of heterochromatins in chromosomes of Taricha are more derived than those of its sister taxon Notophthalmus. Furthermore, the chromosomal NOR types found in the southernmost and northernmost populations of T. granulosa, in the northernmost populations of T. t. sierrae, and in the southern populations of T. t. torosa are recently derived. The implications of this chromosomal variation for phylogeny and biogeography are discussed.

Animals↗
PubMed2006

Enameloid/enamel transition through successive tooth replacements in Pleurodeles waltl (Lissamphibia, Caudata).

Study of the evolutionary enameloid/enamel transition suffers from discontinuous data in the fossil record, although a developmental enameloid/enamel transition exists in living caudates, salamanders and newts. The timing and manner in which the enameloid/enamel transition is achieved during caudate ontogeny is of great interest, because the caudate situation could reflect events that have occurred during evolution. Using light and transmission electron microscopy, we have monitored the formation of the upper tooth region in six successive teeth of a tooth family (position I) in Pleurodeles waltl from late embryos to young adult. Enameloid has only been identified in embryonic tooth I(1) and in larval teeth I(2) and I(3). A thin layer of enamel is deposited later by ameloblasts on the enameloid surface of these teeth. From post-metamorphic juvenile onwards, teeth are covered with enamel only. The collagen-rich enameloid matrix is deposited by odontoblasts, which subsequently form dentin. Enameloid, like enamel, mineralizes and then matures but ameloblast participation in enameloid matrix deposition has not been established. From tooth I(1) to tooth I(3), the enameloid matrix becomes ever more dense and increasingly comes to resemble the dentin matrix, although it is still subjected to maturation. Our data suggest the absence of an enameloid/enamel transition and, instead, the occurrence of an enameloid/dentin transition, which seems to result from a progressive slowing down of odontoblast activity. As a consequence, the ameloblasts in post-metamorphic teeth appear to synthesize the enamel matrix earlier than in larval teeth.

Animals↗
PubMed2006

A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata).

We examine phylogenetic relationships among salamanders of the family Salamandridae using approximately 2700 bases of new mtDNA sequence data (the tRNALeu, ND1, tRNAIle, tRNAGln, tRNAMet, ND2, tRNATrp, tRNAAla, tRNAAsn, tRNACys, tRNATyr, and COI genes and the origin for light-strand replication) collected from 96 individuals representing 61 of the 66 recognized salamandrid species and outgroups. Phylogenetic analyses using maximum parsimony and Bayesian analysis are performed on the new data alone and combined with previously reported sequences from other parts of the mitochondrial genome. The basal phylogenetic split is a polytomy of lineages ancestral to (1) the Italian newt Salamandrina terdigitata, (2) a strongly supported clade comprising the "true" salamanders (genera Chioglossa, Mertensiella, Lyciasalamandra, and Salamandra), and (3) a strongly supported clade comprising all newts except S. terdigitata. Strongly supported clades within the true salamanders include monophyly of each genus and grouping Chioglossa and Mertensiella as the sister taxon to a clade comprising Lyciasalamandra and Salamandra. Among newts, genera Echinotriton, Pleurodeles, and Tylototriton form a strongly supported clade whose sister taxon comprises the genera Calotriton, Cynops, Euproctus, Neurergus, Notophthalmus, Pachytriton, Paramesotriton, Taricha, and Triturus. Our results strongly support monophyly of all polytypic newt genera except Paramesotriton and Triturus, which appear paraphyletic, and Calotriton, for which only one of the two species is sampled. Other well-supported clades within newts include (1) Asian genera Cynops, Pachytriton, and Paramesotriton, (2) North American genera Notophthalmus and Taricha, (3) the Triturus vulgaris species group, and (4) the Triturus cristatus species group; some additional groupings appear strong in Bayesian but not parsimony analyses. Rates of lineage accumulation through time are evaluated using this nearly comprehensive sampling of salamandrid species-level lineages. Rate of lineage accumulation appears constant throughout salamandrid evolutionary history with no obvious fluctuations associated with origins of morphological or ecological novelties.

Animals↗
PubMed2003

Hepatic metallothioneins in two neotenic salamanders, Proteus anguinus and Necturus maculosus (Amphibia, Caudata).

The presence of metallothionein (MT) and the subcellular distribution of copper, zinc and cadmium were investigated in livers of two neotenic salamanders, Proteus anguinus and Necturus maculosus. In P. anguinus, caught in the wild, hepatic MTs were present as a single isoform of (Zn, Cu, Cd)-thioneins, whose molecular weight was estimated to be approximately 12000 by size exclusion chromatography. The percentage of zinc and cadmium was higher in the cytosol and of copper in the pellet. Cytosolic cadmium was almost exclusively associated with MTs (80%), while zinc and copper were also present in the regions of higher-molecular weight proteins. In laboratory bred N. maculosus, MTs were isolated from the liver cytosol and extract of the pellet as (Cu, Zn)- and (Zn, Cu)-thioneins, respectively. According to the low amount of copper extracting from liver pellets of N. maculosus, the presence of water insoluble aggregated forms of Cu-thioneins should be checked in further investigations.

Animals↗
PubMed2005

Pseudoguanolide sesquiterpene lactones from Vernoniopsis caudata and their in vitro antiplasmodial activities.

Two new helenanolide sesquiterpene lactones, 1 and 2, as well as one known related structure, 11alpha,13-dihydrohelenalin-[2-(1-hydroxyethyl)acrylate] (3), together with 4'-beta-d-O-glucopyranosyl-luteolin and ethyl 2,5-dihydroxycinnamate were isolated from an ethyl acetate extract of leaves of Vernoniopsis caudatawith potent antiplasmodial activity (IC50 1.6 microg/mL) in a preliminary biological screen. The structures of the new compounds were determined by spectroscopic techniques. The three sesquiterpene lactones 1-3 displayed strong in vitro antiplasmodial activity, with IC50 values of 1, 0.19, and 0.41 microM, respectively. However, these compounds also exhibited considerable cytotoxicity on KB cells (IC50 < 1 microM in each case).

Antimalarials↗
PubMed1997

Large, rapidly evolving intergenic spacers in the mitochondrial DNA of the salamander family Ambystomatidae (Amphibia: Caudata).

We report the presence, in the mitochondrial DNA (mtDNA) of all of the sexual species of the salamander family Ambystomatidae, of a shared 240-bp intergenic spacer between tRNAThr and tRNAPro. We place the intergenic spacer in context by presenting the sequence of 1,746 bp of mtDNA from Ambystoma tigrinum tigrinum, describe the nucleotide composition of the intergenic spacer in all of the species of Ambystomatidae, and compare it to other coding and noncoding regions of Ambystoma and several other vertebrate mtDNAs. The nucleotide substitution rate of the intergenic spacer is approximately three times faster than the substitution rate of the control region, as shown by comparisons among six Ambystoma macrodactylum sequences and eight members of the Ambystoma tigrinum complex. We also found additional inserts within the intergenic spacers of five species that varied from 87-444 bp in length. The presence of the intergenic spacer in all sexual species of Ambystomatidae suggests that it arose at least 20 MYA and has been a stable component of the ambystomatid mtDNA ever since. As such, it represents one of the few examples of a large and persistent intergenic spacer in the mtDNA of any vertebrate clade.

Ambystoma↗
PubMed2006

Mitochondrial DNA phylogeography of Lissotriton boscai (Caudata, Salamandridae): evidence for old, multiple refugia in an Iberian endemic.

In Europe, southern peninsulas served as refugia during cold periods in the Pleistocene, acting both as centres of origin of endemisms and as sources from which formerly glaciated areas were recolonized during interglacial periods. Previous studies have revealed that within the main refugial areas, intraspecific lineages often survived in allopatric refugia. We analysed two mitochondrial markers (nad4, control region, approximately 1.4 kb) in 103 individuals representing the entire distribution of Lissotriton boscai, a newt endemic to the western Iberian Peninsula. We inferred the evolutionary history of the species through phylogenetic, phylogeographic and historical demographic analyses. The results revealed unexpected, deep levels of geographically structured genetic variability. We identified two main evolutionary lineages, each containing three well-supported clades. The first historical split involved populations from central-southwestern coastal Portugal and the ancestor of all the remaining populations around 5.8 million years ago. Both lineages were subsequently fragmented into different population groups between 2.5 and 1.2 million years ago. According to nested clade analysis, at lower hierarchical levels the patterns suggest restricted gene flow with isolation by distance, whereas at higher levels the clades exhibit signatures of contiguous range expansion. Bayesian Skyline Plots show recent bottlenecks, followed by demographic expansions in all lineages. The significant genetic structure found is consistent with long-term survival of populations in allopatric refugia, supporting the 'refugia-within-refugia' scenario for southern European peninsulas. The comparison of our results with other co-distributed species highlights the generality of this hypothesis for the Iberian herpetofauna and suggests that Mediterranean refuges had more relevance for the composition and distribution of present biodiversity patterns than currently acknowledged. We briefly discuss the taxonomic and conservation implications of our results.

Animals↗
PubMed2001

Effects of hypoxia on egg capsule conductance in Ambystoma (Class Amphibia, Order Caudata).

Aquatic amphibian eggs frequently encounter hypoxic conditions that have the potential to limit oxygen uptake and thereby slow embryonic development and hatching. Oxygen limitation might be avoided if egg capsule surface area and oxygen conductance increased in response to hypoxia. We investigated this possibility in two salamander species, Ambystoma annulatum and Ambystoma talpoideum. The effective surface area of egg capsules increased in response to hypoxia, which increased the conductance for oxygen and enhanced oxygen transport. The ability of amphibian eggs to adjust their conductance in response to oxygen availability may increase survival in hypoxic environments.

Ambystoma↗