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At least 433 records · Page 24Linked to original sources
PubMed2000

Teeth and their sex-dependent dimorphic shape in three species of Costa Rican plethodontid salamanders (Amphibia: Urodela).

The shape of the teeth and their sex-dependent dimorphic expression in three species of Costa Rican plethodontids (Bolitoglossa subpalmata, Oedipina uniformis and Nototriton abscondens) were studied using light microscopy and scanning electron microscopy. The teeth of the vomerine tooth patches are about one third larger than the teeth of the jaws in B. subpalmata and O. uniformis, whereas all teeth of N. abscondens are of about uniform size. The occurrence of bicuspid tooth germs in the fetus proves that primary teeth are bicuspid in these directly developing plethodontids. Females possess only bicuspid teeth consisting of a pedicel and a crown, as is considered characteristic for urodeles after metamorphosis. Adult males possess conical monocuspid teeth on the premaxillary. These teeth--which are similar to the typical late larval tooth of salamanders presenting a larval stage--are about twice as big as the neighbouring bicuspid maxillary teeth. N. abscondens males possess some monocuspid teeth and teeth of aberrant shapes on the premaxillary and the maxillaries. A tendency to build more monocuspid teeth in the premaxillary region than in the maxillary region can be observed in this species. We suppose that different degrees of sensitivity to androgens in each section of the dental lamina of the upper jaw cause the secondary occurrence of conical monocuspid teeth predominantly on the premaxillary section.

Animals↗
PubMed2000

The structure and development of the skull of Costa Rican plethodontid salamanders (Amphibia: Urodela).

We describe the structure of the skulls of the Costa Rican plethodontid salamanders Bolitoglossa subpalmata, Oedipina uniformis and Nototriton abscondens, and the characteristic sequences of development and ossification of the bony elements resulting from direct development using mainly cleared and stained specimens. Significant differences between the species studied are observed. N. abscondens possesses the broadest premaxillary pars dentalis and O. uniformis the narrowest one. The premaxillary dorsal processes are fused over their rostral third only in B. subpalmata; over half their extention in N. abscondens and almost completely in O. uniformis. A prefrontal is always present in N. abscondens; it is hidden underneath the nasal or missing in B. subpalmata, and it is always absent in O. uniformis. The skull bones, with the exception of the orbitosphenoid, develop and ossify sequentially from caudal to rostral in these directly developing species. A more massive pars dentalis of a generally narrower premaxillary are found as typical characters in males.

Aging↗
PubMed2003

The skull structure of six species of Mesoamerican plethodontid salamanders (Amphibia, Urodela).

The skulls of six species of plethodontid salamanders of the genus Bolitoglossa from Costa Rica and Panama, Bolitoglossa colonnea, B. dofleini, B. lignicolor, B. marmorea, B. schizodactyla and B. striatula are comparatively analysed. All species are terrestrial or slightly arboreal and show no life-mode-dependent skull characteristics. Heads cleared by transparent preparation and stained in toto were used for examination of the skull structure and paraffin sections of the gonads were prepared to confirm sexual maturity of each individual. Focussing on the size of the premaxillary pars dentalis, the degree of fusion of the processus dorsales praemaxillares and the presence or absence of the paired prefrontals we state that B. dofleini and B. striatula possess more ancestral characteristics, B. marmorea is situated in an intermediate position and B. colonnea, B. lignicolor and B. schizodactyla show more advanced characteristics.

Animals↗
PubMed2004

Gender-dependent dimorphic teeth in four species of Mesoamerican plethodontid salamanders (Urodela, Amphibia).

The tooth shapes of premaxillary and maxillary teeth of adults of four Mesoamerican salamander species (Urodela, Plethodontidae) were examined. Using scanning electron microscopy we determined whether the monocuspid teeth that are present only on the premaxillary of sexually mature males belong to the conical, unbladed, monocuspid tooth type found in urodele larvae or whether they represent morphological variations of the typical, bladed, bicuspid teeth of metamorphosed individuals. The teeth of some studied species are, in fact, unbladed and in some cases show one very reduced tip. But none of the studied teeth is per definitionem monocuspid and no tooth shows an enameloid layer between dentine shaft and enamel cap, which is always present in the teeth of early urodele larvae. The "monocuspid" teeth of adult males of Mesoamerican plethodontid salamanders have to be considered a morphological variation of the metamorphosed, bicuspid tooth type typical for metamorphosed urodeles.

Animals↗
PubMed2004

Separated dental laminae are present in the upper jaw of Mesoamerican lungless salamanders (Amphibia, Plethodontidae).

Plethodontid salamander species from Northern America exhibit a single, unseparated dental lamina in the upper jaw, which consistently provides teeth for the unpaired premaxillary and the two maxillary bones. During the distinct mating season, adult males of these species bear long, monocuspid, unbladed teeth in the entire upper jaw, which are used during courtship. However, plethodontid salamander species from Southern Central America studied so far show either three separated dental laminae or a single dental lamina with three distinguishable tooth-producing parts connected by non-producing parts. These species reproduce aseasonally and sexually mature males permanently bear long, monocuspid, unbladed teeth on the premaxillary only. As the formation of these long, monocuspid teeth depends on the presence of androgen-receptors in the tooth-forming tissues, the morphological separation of the dental lamina in plethodontid salamanders from Southern Central America is very likely to be a prerequisite for a region-specific expression of androgen-receptors in the tooth-forming tissues controlling the differentiated shape formation of teeth in these species. Seven species of plethodontid salamanders from Costa Rica and Panama were examined and, in all, a tendency to exhibit three separate dental lamina in the upper jaw was found, although the morphological separation is definitive only in Bolitoglossa colonnea, B. lignicolor, B. pesrubra, B. schizodactyla and B. striatula. B. dofleini and B. marmorea show a continuous dental lamina with non-producing parts at the transitional sites between the parts associated with the premaxillary and the maxillary bones.

Animals↗
PubMed2002

Phylogenetic relationships of Indian caecilians (Amphibia: Gymnophiona) inferred from mitochondrial rRNA gene sequences.

India has a diverse caecilian fauna, including representatives of three of the six currently recognized families, the Caeciliidae, Ichthyophiidae, the endemic Uraeotyphlidae, but previous molecular phylogenetic studies of caecilians have not included sequences for any Indian caecilians. Partial 12S and 16S mitochondrial gene sequences were obtained for a single representative of each of the caecilian families found in India and aligned against previously reported sequences for 13 caecilian species. The resulting alignment (16 taxa, 1200 sites, of which 288 cannot be aligned unambiguously) was analyzed using parsimony, maximum-likelihood, and distance methods. As judged by bootstrap proportions, decay indices, and leaf stabilities, well-supported relationships of the Indian caecilians are recovered from the alignment. The data (1) corroborate the hypothesis, based on morphology, that the Uraeotyphlidae and Ichthyophiidae are sister taxa, (2) recover a monophyletic Ichthyophiidae, including Indian and South East Asian representatives, and (3) place the Indian caeciliid Gegeneophis ramaswamii as the sister group of the caeciliid caecilians of the Seychelles. Rough estimates of divergence times suggest an origin of the Uraeotyphlidae and Ichthyophiidae while India was isolated from Laurasia and Africa and are most consistent with an Indian origin of these families and subsequent dispersal of ichthyophiids into South East Asia.

Amphibians↗
PubMed2003

Climatic oscillations triggered post-Messinian speciation of Western Palearctic brown frogs (Amphibia, Ranidae).

Oscillating glacial cycles over the past 2.4 million years are proposed to have had a major impact on the diversity of contemporary species communities. We used mitochondrial and nuclear DNA sequence data to infer phylogenetic relationships within Western Palearctic brown frogs and to test the influence of Pliocene and Pleistocene climatic changes on their evolution. We sequenced 1976bp of the mitochondrial genes 16S rRNA and cytochrome b and of the nuclear rhodopsin gene for all current species and subspecies. Based on an established allozyme clock for Western Palearctic water frogs and substitution rate constancy among water frogs and brown frogs, we calibrated a molecular clock for 1425bp of the 16S and rhodopsin genes. We applied this clock to date speciation events among brown frogs. Western Palearctic brown frogs underwent a basal post-Messinian radiation about 4 million years ago (mya) into five major clades: three monotypic lineages (Rana dalmatina, Rana latastei, Rana graeca), an Anatolian lineage, and a lineage comprising Rana italica, Rana arvalis, and all Iberian taxa. Polytypic lineages radiated further in concordance with the onset of climatic oscillations ca. 3.2, 2.0, and 1.0-0.6 mya, respectively. The dated fossil record corroborates our paleobiogeographic scenario. We conclude that drastic climatic changes followed by successive temperature oscillations "trapped" most brown frog species in their southern European glacial refugia with enough time to speciate. Substantial dispersal was only possible during extensive interglacial periods of a constant subtropical climate.

Animals↗
PubMed2000

Inability of adult Limnodynastes peronii (Amphibia: Anura) to thermally acclimate locomotor performance.

Despite several studies on adult amphibians, only larvae of the striped marsh frog (Limnodynastes peronii) have been reported to possess the ability to compensate for the effects of cool temperature on locomotor performance by thermal acclimation. In this study, we investigated whether this thermal acclimatory ability is shared by adult L. peronii. We exposed adult L. peronii to either 18 or 30 degrees C for 8 weeks and tested their swimming and jumping performance at six temperatures between 8 and 35 degrees C. Acute changes in temperature affected both maximum swimming and jumping performance, however there was no difference between the two treatment groups in locomotor performance between 8 and 30 degrees C. Maximum swimming velocity of both groups increased from 0.62+/-0.02 at 8 degrees C to 1.02+/-0.03 m s(-1) at 30 degrees C, while maximum jump distance increased from approximately 20 to >60 cm over the same temperature range. Although adult L. peronii acclimated to 18 degrees C failed to produce a locomotor response at 35 degrees C, this most likely reflected a change in thermal tolerance limits with acclimation rather than modifications in the locomotor system. As all adult amphibians studied to date are incapable of thermally acclimating locomotor performance, including adults of L. peronii, this acclimatory capacity appears to be absent from the adult stage of development.

Adaptation, Physiological↗
PubMed2001

Systematic status of Hynobius tokyoensis (Amphibia: Urodela) from Aichi Prefecture, Japan: a biochemical survey.

Taxonomic status of a salamander now identified as Hynobius tokyoensis from Aichi Prefecture, Japan, was assessed by allozymic comparisons with its relatives. All three populations of H. tokyoensis from Aichi formed a monophyletic group with populations of H. nebulosus; this group is substantially diverged from a conspecific population from Kanagawa that formed another group with H. lichenatus. In the former group, the population of H. nebulosus from near the type locality was more divergent from the other conspecific populations than were three populations of H. tokyoensis from Aichi. It is quite clear that the salamander from Aichi now identified as H. tokyoensis is genetically much closer to H. nebulosus than to H. tokyoensis from Kanagawa, which is closest geographically to its type locality. This result conforms well to reported results of morphological and genetic studies, and the salamander from Aichi, now called H. tokyoensis, should be identified as H. nebulosus, which is sufficiently diverged from H. tokyoensis to be considered a distinct species.

Algorithms↗
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↗
PubMed1998

Dynamics of natural infections of Rhabdias cf. hylae (Nematoda) in Bufo marinus (Amphibia) in Australia.

Infrapopulation dynamics of the nematode Rhabdias cf. hylae within naturally-infected Bufo marinus in north Queensland, Australia, were detailed. Over 80% of 580 toads were infected with Rh. cf. hylae with a mean intensity of 16.1. Distribution of Rh. cf. hylae within the toad population was aggregated, with an increase in the variance-to-mean ratio with increasing toad size. Intensity of infection and length of nematode were both correlated with length of toad in the smaller size classes. Length of nematode was not related to intensity of infection at any time. Mean intensity of infection rose significantly in small toads following initial infection after metamorphosis. Over the same period, average length of nematode did not increase implying constant re-infection of the toads. Larger toads were not reinfected to the same extent, and the number of uninfected toads in the larger size class increased which indicated a natural loss of infections. Changes in parameters of Rh. cf. hylae infection within B. marinus were attributed to seasonal rainfall and its subsequent effect on the behaviour of the toad.

Analysis of Variance↗
PubMedDate not supplied

Membrane current of retinal rods of Caudiverbera caudiverbera (Amphibia: Leptodactylidae): dark noise, spectral and absolute light sensitivity.

We investigated the photocurrents from isolated rods of the South American anuran, Caudiverbera caudiverbera. Rod outer segments were on average 66.4 +/- 11.2 microm (mean +/- S.D., n = 104) in length and 6.6 +/- 0.9 microm (mean +/- S.D.) in diameter: 40 +/- 22 photoisomerizations (mean +/- S.D., range 10-99, n = 16) were required for eliciting a half-saturating photocurrent response. The time-to-peak was 911 +/- 217 ms (mean +/- S.D., n = 14, 20 degrees C) in the linear range of the response and the integration time of the current response was 1744 +/- 451 ms (mean +/- S.D., n = 14). The time-to-peak appears to be slower and the integration time shorter in Caudiverbera than in Ambystoma tigrinum, Rana pipiens or Xenopus laevis rods under similar experimental conditions. The a-band of rod spectral sensitivity has a lambda(max) at 520 +/- 2.1 nm (mean +/- S.D., range 516-525 nm, n = 24) and the bandwidth fits a porphyropsin visual pigment. The single-event response amplitude ranges from 0.31-0.51 pA, depending on the calculation method. The intrinsic dark current (variance at dark minus variance under bright light) was 0.045 +/- 0.040 pA2 (mean +/- S.D., n = 24). Our results support the presence of a dark-noise component below 1 Hz, with kinetics similar to the single-photon evoked response and a rate of 0.006 events s(-1) (n = 9).

Amphibians↗
PubMed1998

Identification of enhancer-like elements in the ribosomal intergenic spacer of Odontophrynus americanus 2n and 4n (Amphibia, Anura).

Repetitive elements are found in the ribosomal intergenic spacer (IGS) of most organisms. A particularly complex pattern of internal repetition occurs in the IGSs of O. americanus 2n and 4n, which are composed of several types of BamHI subrepeats (B-SRs). The most repetitive one is approximately 87 bp long, and is highly represented in the IGS variants of these amphibians. Sequence analyses of six diploid and two tetraploid B-SRs show 87% and 86% homology, respectively, and related secondary structure predictions. The comparison of the 2n and 4n B-SR sequences aligned with the 81 bp enhancer of Xenopus laevis reveals 36% homology. Furthermore, other B-SR features like size, number, and secondary structures resemble those of Xenopus enhancers, suggesting that B-SRs may function as regulators of O. americanus rDNA transcription. The present data also corroborate the close evolutionary relationship between 2n and 4n O. americanus species.

Animals↗
PubMed1998

Polymorphism of the nucleolus organizer regions (NORs) in Physalaemus petersi (Amphibia, Anura, Leptodactylidae) detected by silver staining and fluorescence in situ hybridization.

The nucleolus organizer regions (NORs) of both karyotypes I and II of Physalaemus petersi (Jiménez de la Espada, 1872) from the Brazilian Amazon were studied by Giemsa staining, and by the Ag-NOR method. Karyological group I specimens were also studied by the fluorescence in situ hybridization (FISH) technique. Multiple NOR-bearing chromosomes were detected in both karyotypes. The coincident results of the Ag-NOR and FISH methods rule out the occurrence of silent NORs in this anuran. There was no intraindividual NOR variability in either group, but interindividual variability of NORs was high in group I. Seven different patterns of active NOR distribution were definitely recognized among fifteen specimens. This was considered to be a NOR site polymorphism. These results, combined with the C-band polymorphism previously reported for P. petersi, demonstrate a high rate of chromosome evolution in this group.

Animals↗
PubMed2000

Chromosomal rearrangements as the source of variation in the number of chromosomes in Pseudis (Amphibia, Anura).

A cytogenetic study of Pseudis specimens from three localities in Rio Grande do Sul State, the southernmost Brazilian, was performed to identify karyotypic characteristics that could account for differences in vocalization pattern and body size. Individuals from around Tainhas were compared to those of São Jerĵnimo and Eldorado do Sul. Specimens from these latter two localities were identified as Pseudis minuta, while those from the former were classified as Pseudis sp. (aff minuta). The populations from São Jerĵnimo and Eldorado do Sul had 2n = 24 chromosomes, classified as metacentric. submetacentric and subtelocentric. The population from Tainhas had 2n = 28 chromosomes, with four pairs of telocentric chromosomes. Modelling of these 28 chromosomes and testing for fusion in the centromeric/telomeric regions yielded a karyotype of 2n = 24 chromosomes, similar to that of the other populations. The similarity was reinforced by the location of the NORs and heterochromatin. The Tainhas population showed an increase in heterochromatin, as seen by the presence of additional C-bands, especially in the telocentric chromosomes. These data suggest that the two karyotypes described in this work had a common ancestry. There is evidence that the differentiation of these karyotypes may have occurred by chromosome fission and heterochromatin addition. Based on the present karyotype (2n = 28) and on morphological and vocalization studies by other researchers, we conclude that the Tainhas population may represent a new species.

Animals↗
PubMed1997

Genetic variation in some populations of the golden-striped salamander, Chioglossa lusitanica (Amphibia: Urodela), in Portugal.

Genetic variation in the golden-striped salamander (Chioglossa lusitanica) was assessed in 231 individuals from four Portuguese populations by means of horizontal starch gel electrophoresis and isoelectric focusing. Three of 19 enzyme systems, representing 21 presumptive loci, were found to be polymorphic: phosphoglucomutase 1 (PGM1), peptidase B (PEPB), and peptidase D (PEPD). The observed average heterozygosity in Chioglossa lusitanica (0.027) is significantly lower than that observed for other amphibians, either urodeles or salamandrids. Differences in allele frequencies and the presence of private alleles are indicative of a high degree of population differentiation. PEPD, in particular, seems to be a diagnostic locus separating the southernmost population studied from the others.

Aminopeptidases↗