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1.
Oecologia ; 193(4): 879-888, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32740730

RESUMO

Size thresholds commonly underlie the induction of alternative morphological states. However, the respective importance of absolute and relative size to such thresholds remains uncertain. If absolute size governs expression, morph frequency should differ among environments that influence absolute sizes (e.g. resources, competition), and individuals of the same morph should have similar average sizes across environments. If relative size determines expression, the frequency of each morph may not differ among environments, but morphs within each environment should differ in size relative to one another. We tested these predictions in a salamander (Ambystoma talpoideum) that develops into either a terrestrial metamorph or an aquatic paedomorph. To generate size variation within and among environments, we reared individuals in mesocosm ponds across three conspecific densities. We found that morph frequency did not differ among density treatments, and the morphs were not similarly sized within each density treatment. Instead, within each environment, relatively larger individuals became metamorphs and relatively smaller individuals became paedomorphs. Relative size therefore determined morph development, highlighting the importance of an individual's social context to size-dependent morph induction.


Assuntos
Ambystoma , Urodelos , Ambystomatidae , Animais , Larva , Metamorfose Biológica
2.
Oecologia ; 183(3): 739-749, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28083660

RESUMO

Plasticity in life history strategies can be advantageous for species that occupy spatially or temporally variable environments. We examined how phenotypic plasticity influences responses of the mole salamander, Ambystoma talpoideum, to disturbance events at the St. Marks National Wildlife Refuge (SMNWR), FL, USA from 2009 to 2014. We observed periods of extensive drought early in the study, in contrast to high rainfall and expansive flooding events in later years. Flooding facilitated colonization of predatory fishes to isolated wetlands across the refuge. We employed multistate occupancy models to determine how this natural experiment influenced the occurrence of aquatic larvae and paedomorphic adults and what implications this may have for the population. We found that, in terms of occurrence, responses to environmental variation differed between larvae and paedomorphs, but plasticity (i.e. the ability to metamorphose rather than remain in aquatic environment) was not sufficient to buffer populations from declining as a result of environmental perturbations. Drought and fish presence negatively influenced occurrence dynamics of larval and paedomorphic mole salamanders and, consequently, contributed to observed short-term declines of this species. Overall occurrence of larval salamanders decreased from 0.611 in 2009 to 0.075 in 2014 and paedomorph occurrence decreased from 0.311 in 2009 to 0.121 in 2014. Although variation in selection pressures has likely maintained this polyphenism previously, our results suggest that continued changes in environmental variability and the persistence of fish in isolated wetlands could lead to a loss of paedomorphosis in the SMNWR population and, ultimately, impact regional persistence in the future.


Assuntos
Ambystomatidae , Metamorfose Biológica , Ambystoma , Animais , Meio Ambiente , Larva
3.
J Genet ; 96(6): 873-883, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29321345

RESUMO

Amphibians are globally threatened by habitat loss and fragmentation; species within the order Ambystoma are not the exception, as there are 18 species of mole salamanders in México, of which 16 are endemic and all species are under some national or international status of protection. The mole salamander, Ambystoma altamirani is a microendemic species, which is distributed in central México, within the trans-Mexican volcanic belt, and is one of the most threatened species due to habitat destruction and the introduction of exotic species. Nine microsatellite markers were used to determine the genetic structure, genetic variability, effective population size, presence of bottlenecks and inbreeding coefficient of one population of A. altamirani to generate information which might help to protect and conserve this threatened species. We found two genetic subpopulations with significant level of genetic structure (FST = 0.005) and high levels of genetic variability (Ho = 0.883; He = 0.621); we also found a small population size (Ne = 8.8), the presence of historical (M = 0.486) and recent bottlenecks under IAM and TPM models, with a low, but significant coefficient of inbreeding (FIS = -0.451). This information will help us to raise conservation strategies of this microendemic mole salamander species.


Assuntos
Ambystomatidae/genética , Variação Genética , Genética Populacional , Animais , Ecossistema , Espécies em Perigo de Extinção , Fluxo Gênico , Endogamia , México , Repetições de Microssatélites/genética , Densidade Demográfica
4.
Genetica ; 144(6): 689-698, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27796527

RESUMO

Human activities are affecting the distribution of species worldwide by causing fragmentation and isolation of populations. Isolation and fragmentation lead to populations with lower genetic variability and an increased chance of inbreeding and genetic drift, which results in a loss of biological fitness over time. Studies of the genetic structure of small and isolated populations are critically important for management and conservation decisions. Ambystoma rivulare is a micro-endemic Mexican mole salamander from central Mexico. It is found in the most ecologically disturbed region in Mexico, the Trans-Mexican Volcanic Belt. The goal of this study of the population genetics of the micro-endemic mole salamander was to provide information to be used as a basis for future research and conservation planning of this species and other species of the Ambystoma genus in Mexico. The structural analysis found two subpopulations, one for each river sampled, with no signs of admixture and very high levels of genetic differentiation. Medium to high levels of heterozygosity and few alleles and genotypes were observed. Evidence of an ancestral genetic bottleneck, low values of effective population size, small inbreeding coefficients, and low gene flow were also found.


Assuntos
Ambystomatidae/genética , Variação Genética , Animais , Conservação dos Recursos Naturais , Fluxo Gênico , México , Filogenia , Densidade Demográfica
5.
PLoS One ; 9(7): e103595, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25076052

RESUMO

The reduced immigration and emigration rates resulting from the lack of landscape connectivity of patches and the hospitality of the intervening matrix could favor the loss of alleles through genetic drift and an increased chance of inbreeding. In order for isolated populations to maintain sufficient levels of genetic diversity and adapt to environmental changes, one important conservation goal must be to preserve or reestablish connectivity among patches in a fragmented landscape. We studied the last known population of Ambystoma leorae, an endemic and critically threatened species. The aims of this study were: (1) to assess the demographic parameters of A. leorae and to distinguish and characterize the microhabitats in the river, (2) to determine the number of existing genetic groups or demes of A. leorae and to describe possible relationships between microhabitats types and demes, (3) to determine gene flow between demes, and (4) to search for geographic locations of genetic discontinuities that limit gene flow between demes. We found three types of microhabitats and three genetically differentiated subpopulations with a significant level of genetic structure. In addition, we found slight genetic barriers. Our results suggest that mole salamander's species are very sensitive to microhabitat features and relatively narrow obstacles in their path. The estimates of bidirectional gene flow are consistent with the pattern of a stepping stone model between demes, where migration occurs between adjacent demes, but there is low gene flow between distant demes. We can also conclude that there is a positive correlation between microhabitats and genetic structure in this population.


Assuntos
Ambystoma/genética , Alelos , Ambystomatidae , Distribuição Animal , Animais , Análise por Conglomerados , Ecossistema , Espécies em Perigo de Extinção , Fluxo Gênico , Deriva Genética , Variação Genética , Endogamia , México , Repetições de Microssatélites , Modelos Genéticos , Rios
6.
Mol Phylogenet Evol ; 68(3): 671-82, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23632032

RESUMO

The analysis of diverse data sets can yield different phylogenetic estimates that challenge systematists to explain the source of discordance. The mole salamanders (family Ambystomatidae) are a classic example of this phylogenetic conflict. Previous attempts to resolve the ambystomatid species tree using allozymic, morphological, and mitochondrial sequence data have yielded different estimates, making it unclear which data source best approximates ambystomatid phylogeny and which ones yield phylogenetically inaccurate reconstructions. To shed light on this conflict, we present the first multi-locus DNA sequence-based phylogenetic study of the Ambystomatidae. We utilized a range of analyses, including coalescent-based methods of species-tree estimation that account for incomplete lineage sorting within a locus and concordance-based methods that estimate the number of sampled loci that support a particular clade. We repeated these analyses with the removal of individual loci to determine if any locus has a disproportionate effect on our phylogenetic results. Collectively, these results robustly resolved many deep and relatively shallow clades within Ambystoma, including the placement of A. gracile and A. talpoideum as the sister clade to a clade containing all remaining ambystomatids, and the placement of A. maculatum as the sister lineage to all remaining ambystomatids excluding A. gracile and A. talpoideum. Both Bayesian coalescent and concordance methods produced similar results, highlighting strongly supported branches in the species tree. Furthermore, coalescent-based analyses that excluded loci produced overlapping species-tree posterior distributions, suggesting that no particular locus--including mtDNA--disproportionately contributed to our species-tree estimates. Overall, our phylogenetic estimates have greater similarity with previous allozyme and mitochondrial sequence-based phylogenetic estimates. However, intermediate depths of divergence in the ambystomatid species tree remain unresolved, potentially highlighting a region of rapid species radiation or a hard polytomy, which limits our ability to comment on previous morphologically-based taxonomic groups.


Assuntos
Ambystomatidae/genética , Loci Gênicos , Animais , Teorema de Bayes , DNA Mitocondrial , Evolução Molecular , Tipagem de Sequências Multilocus , Filogenia
7.
Gene ; 349: 43-53, 2005 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-15780978

RESUMO

We report on a study that extended mitochondrial transcript information from a recent EST project to obtain complete mitochondrial genome sequence for 5 tiger salamander complex species (Ambystoma mexicanum, A. t. tigrinum, A. andersoni, A. californiense, and A. dumerilii). We describe, for the first time, aspects of mitochondrial transcription in a representative amphibian, and then use complete mitochondrial sequence data to examine salamander phylogeny at both deep and shallow levels of evolutionary divergence. The available mitochondrial ESTs for A. mexicanum (N=2481) and A. t. tigrinum (N=1205) provided 92% and 87% coverage of the mitochondrial genome, respectively. Complete mitochondrial sequences for all species were rapidly obtained by using long distance PCR and DNA sequencing. A number of genome structural characteristics (base pair length, base composition, gene number, gene boundaries, codon usage) were highly similar among all species and to other distantly related salamanders. Overall, mitochondrial transcription in Ambystoma approximated the pattern observed in other vertebrates. We inferred from the mapping of ESTs onto mtDNA that transcription occurs from both heavy and light strand promoters and continues around the entire length of the mtDNA, followed by post-transcriptional processing. However, the observation of many short transcripts corresponding to rRNA genes indicates that transcription may often terminate prematurely to bias transcription of rRNA genes; indeed an rRNA transcription termination signal sequence was observed immediately following the 16S rRNA gene. Phylogenetic analyses of salamander family relationships consistently grouped Ambystomatidae in a clade containing Cryptobranchidae and Hynobiidae, to the exclusion of Salamandridae. This robust result suggests a novel alternative hypothesis because previous studies have consistently identified Ambystomatidae and Salamandridae as closely related taxa. Phylogenetic analyses of tiger salamander complex species also produced robustly supported trees. The D-loop, used in previous molecular phylogenetic studies of the complex, was found to contain a relatively low level of variation and we identified mitochondrial regions with higher rates of molecular evolution that are more useful in resolving relationships among species. Our results show the benefit of using complete genome mitochondrial information in studies of recently and rapidly diverged taxa.


Assuntos
Ambystomatidae/genética , DNA Mitocondrial , Genoma , Filogenia , Transcrição Genética , Animais , Sequência de Bases , Teorema de Bayes , Mapeamento de Sequências Contíguas , Evolução Molecular , Etiquetas de Sequências Expressas , Genes de RNAr , Polimorfismo Genético , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico
8.
Vision Res ; 42(1): 19-27, 2002 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-11804628

RESUMO

Light-evoked postsynaptic currents (lePSCs) were recorded from ON, OFF and ON-OFF ganglion cells in dark-adapted salamander retinal slices under voltage clamp conditions, and the cell morphology was examined using Lucifer yellow fluorescence with confocal microscopy. The current-voltage relations of the lePSCs in all three types of ganglion cells are approximately linear within the cells' physiological range. The average chloride/cation conductance ratio (Deltag(Cl)(NR)/Deltag(C)(NR)) of the lePSCs is near 3, suggesting that ganglion cell light responses are associated with a greater postsynaptic conductance change at the amacrine-ganglion cell inhibitory synapses than at the bipolar-ganglion cell excitatory synapses. By comparing the charge transfer of lePSCs in normal Ringer's and in picrotoxin+strychnine+Imidazole-4-acidic acid, we found that the GABAergic and glycinergic amacrine-bipolar cell feedback synapses decreased the light-induced glutamatergic vesicle release from bipolar cells to all ganglion cells, and the degree of release reduction varied widely from ganglion cell to ganglion cell, with a range of 3-28 fold.


Assuntos
Gânglios Sensitivos/fisiologia , Retina/fisiologia , Visão Ocular/fisiologia , Ambystomatidae , Animais , Cloretos/fisiologia , Condutividade Elétrica , Imidazóis/farmacologia , Microscopia Confocal , Técnicas de Patch-Clamp , Picrotoxina/farmacologia , Estricnina/farmacologia , Transmissão Sináptica/fisiologia
9.
Proc Natl Acad Sci U S A ; 95(10): 5643-8, 1998 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-9576937

RESUMO

Morphological features such as size and shape are the most common focus in studies of heterochronic change. Frequently, these easily observed and measured features are treated as a major target of selection, potentially ignoring traits more closely related to fitness. We question the primacy of morphological data in studies of heterochrony, and instead suggest that principal sources of fitness, such as life history characteristics, are not only the chief targets of selection, but changes in them may necessitate changes in other (subordinate) elements of the organism. We use an experimental approach to investigate the timing of metamorphosis and maturation in a facultatively paedomorphic salamander, Ambystoma talpoideum. We determine that individuals possessing the well-known paedomorphic phenotype are peramorphic with regard to maturation, through the process of predisplacement (an earlier onset of maturation). Combining the well studied ecology of dimorphic A. talpoideum populations with theories of heterochronic mechanisms and life history evolution, we conclude that age at maturation is the principal target of selection and that morphological changes are secondary effects. Increased attention to the intimate connection between life history evolution and heterochrony is the most promising route to a better understanding of both.


Assuntos
Ambystomatidae/crescimento & desenvolvimento , Metamorfose Biológica/fisiologia , Diferenciação Sexual/fisiologia , Animais , Feminino , Masculino , Fenótipo , Especificidade da Espécie
10.
Mol Biol Evol ; 14(11): 1167-76, 1997 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-9364774

RESUMO

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.


Assuntos
Ambystomatidae/genética , DNA Mitocondrial/genética , Evolução Molecular , Ambystoma/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Elementos de DNA Transponíveis/genética , DNA Ribossômico/genética , Modelos Genéticos , Dados de Sequência Molecular , Filogenia , RNA de Transferência de Prolina/genética , RNA de Transferência de Treonina/genética , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie
11.
Dev Biol ; 175(2): 265-82, 1996 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-8626032

RESUMO

In many species of salamanders, pigment cells derived from the neural crest give rise to a horizontal stripe pattern in hatchling larvae. A defining element of these horizontal stripe patterns is a region over the middle of the myotomes that is relatively free of melanophores. This study shows that formation of a "melanophore-free region" and horizontal stripe pattern in Ambystoma tigrinum tigrinum (family Ambystomatidae) correlates with the development of the trunk lateral line sensory system. Moreover, prevention of lateral line development results in greater densities of melanophores in the middle of the flank, essentially eliminating the melanophore-free region in this taxon. A phylogenetic survey also revealed that ablation of the lateral lines has qualitatively similar effects on melanophores in seven of eight additional taxa (Ambystomatidae: A. barbouri, A. maculatum, A. talpoideum; Salamandridae: Notophthalmus viridescens, Pleurodeles waltl, Taricha granulosa, T. rivularis). In Taricha torosa, however, a superficially similar melanophore-free region forms prior to lateral line development, and ablation of the lateral lines does not perturb the horizontal stripe pattern. Finally, heterospecific grafting experiments demonstrated that T. torosa lateral lines are competent to generate a melanophore-free region, and T. torosa melanophores are competent to respond to cues associated with the lateral lines. These results indicate that lateral line-dependent pattern-forming mechanisms are common and probably ancestral within the families Ambystomatidae and Salamandridae and suggest that these ancestral mechanisms have been retained in T. torosa as redundant, lateral line-dependent mechanisms for stripe formation have evolved.


Assuntos
Ambystomatidae/crescimento & desenvolvimento , Melanóforos/fisiologia , Órgãos dos Sentidos/fisiologia , Pigmentação da Pele/fisiologia , Ambystomatidae/embriologia , Ambystomatidae/fisiologia , Animais , Embrião não Mamífero/ultraestrutura , Desenvolvimento Embrionário , Larva/crescimento & desenvolvimento , Larva/ultraestrutura , Filogenia , Órgãos dos Sentidos/crescimento & desenvolvimento , Especificidade da Espécie
12.
J Neurosci Methods ; 62(1-2): 159-68, 1995 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-8750098

RESUMO

A method for evoking neurotransmitter release without light stimulation has been developed and applied to a retinal slice preparation of the tiger salamander (Ambystoma Tigrum). This method utilizes a micropipette containing hyperosmotic levels of sucrose in Ringer, positioned within the inner plexiform layer (IPL) under visual control. Intermittent pressure (between 0.1 and 2 bars) applied to the pipette evoked release of neurotransmitters which were evaluated with whole-cell recording (WCR) technique applied to cells in the ganglion cell layer. Pharmacological studies were used to characterize the properties of the hyperosmotic sucrose-evoked response (HSER) and in some cases, we compared the HSER with synaptic currents evoked by light stimulation. The HSER typically consisted of both inhibitory and excitatory components with a reversal potential in between that for chloride (approximately -60 mV) and non-specific cation channels (approximately 0 mV). Relatively pure inhibition or excitation could be revealed through pharmacological techniques by blocking the inhibition with picrotoxin/strychnine or by blocking the glutamatergic neurotransmission with D-AP7 (D-2-amino-7-phosphonoheptanoate) and NBQX (2,3-dihydroxy-6-nitro-sulfamoyl -benzo (F) quinoxaline). A comparison of light-evoked responses (LER) and the HSER suggested that they activate the same pool of releasable neurotransmitter.


Assuntos
2-Amino-5-fosfonovalerato/análogos & derivados , Neurotransmissores/metabolismo , Terminações Pré-Sinápticas/metabolismo , Células Ganglionares da Retina/fisiologia , Ambystomatidae , Aminoácidos/farmacologia , Animais , Anticonvulsivantes/farmacologia , Cádmio/farmacologia , Cobalto/farmacologia , Convulsivantes/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Luz , Potenciais da Membrana/efeitos dos fármacos , Neurotransmissores/antagonistas & inibidores , Técnicas de Cultura de Órgãos , Pressão Osmótica , Técnicas de Patch-Clamp , Picrotoxina/farmacologia , Quinoxalinas/farmacologia , Células Ganglionares da Retina/efeitos dos fármacos , Estricnina/farmacologia , Sacarose/farmacologia
13.
J Morphol ; 212(3): 305-22, 1992 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-1507243

RESUMO

Histology of the cloacae of Rhyacotriton olympicus and representative species from the genera Ambystoma and Dicamptodon was examined by light microscopy. Females of Ambystoma possess sperm storage glands, the spermathecae, as well as ventral glands and dorsal glands, both of uncertain function. Females of Ambystoma examined from the subgenus Linguaelapsus differ from those in the subgenus Ambystoma by possessing more extensive ventral gland clusters and a shorter cloacal tube. Females of Dicamptodon possess spermathecae and ventral glands, but differ in cloacal conformation from females of Ambystoma and lack the dorsal glands. Females of R. olympicus possess more extensive epidermal lining in the cloaca than that found in females of Ambystoma and Dicamptodon, and the only glands present are spermathecae, which cluster around a tube in the dorsal roof. Males of Ambystoma, Dicamptodon, and R. olympicus possess five types of cloacal glands (dorsal pelvic glands, lateral pelvic glands, anterior ventral glands, posterior ventral glands, and Kingsbury's glands) that function in spermatophore formation, and vent glands that may produce a courtship pheromone. In Ambystoma and Dicamptodon, vent glands secrete along the medial borders of the cloacal orifice. Males of A. opacum and A. talpoideum differ from males of other species examined from the two genera by possessing more extensive vent glands. Males of R. olympicus possess unique vent glands in which tubules secrete onto the surface of vent lobes lateral to the posterior end of the cloacal orifice, and distal ends of the glands pass anteriorly, superficial to the fascia enclosing the other cloacal glands. The results from analysis of cloacal anatomy support other data indicating that Ambystoma and Dicamptodon are sister groups, and that Rhyacotriton olympicus is not closely related to either of the other two genera and merits placement in a separate family.


Assuntos
Ambystomatidae/anatomia & histologia , Cloaca/anatomia & histologia , Filogenia , Animais , Feminino , Masculino , Modelos Anatômicos , Caracteres Sexuais
14.
J Anat ; 179: 1-8, 1991 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-1817128

RESUMO

Different conditions in the arrangement of the adrenal gland are observed in urodeles. The gland consists of islets scattered on the ventral surface of the kidneys, the amount, size and position of the islets varying consistently within different families and even within genera. The infraordinal variation also extends to the fine structure of the gland, as observed in 14 species belonging to 6 different families. The ultrastructural characteristics of chromaffin cells and their relationships with interrenal cells appear to be related to the phyletic position. In primitive urodeles (Sirenidae, Proteidae) the chromaffin cells are isolated or in small groups, mostly separated from interrenal cells and often in contact with renal cells. In neourodeles (Amphiumidae, Ambystomidae, Salamandridae, Plethodontidae) the chromaffin cells appear generally grouped and intermingled with steroidogenic cells. Some cytological characteristics of chromaffin cells, such as nerve supply and the shape and electron density of chromaffin granules exhibit a variability related to phyletic position.


Assuntos
Sistema Cromafim/citologia , Urodelos/anatomia & histologia , Glândulas Suprarrenais/citologia , Ambystomatidae/anatomia & histologia , Animais , Fibras Colinérgicas/ultraestrutura , Grânulos Cromafim/ultraestrutura , Sistema Cromafim/inervação , Sistema Cromafim/metabolismo , Sistema Cromafim/ultraestrutura , Feminino , Glândula Inter-Renal/citologia , Masculino , Microscopia Eletrônica , Proteidae/anatomia & histologia , Salamandridae/anatomia & histologia , Especificidade da Espécie , Esteroides/metabolismo
15.
J Morphol ; 187(2): 181-99, 1986 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-3959085

RESUMO

The morphology and fine structure of the basilar recess and basilar papilla were investigated in four species of salamanders from the family Ambystomatidae. The otic relationships of the recess and papilla to the proximal part of the lagena and saccule are described, and new terminology is suggested for the periotic relationships of the basilar recess to a diverticulum of an intracapsular periotic sac. The basilar papilla consists of supporting cells united laterally by gap junctions, capped by microvilli uniformly arranged around a short, central cilium, and hair cells that typically show several synapses with a single afferent nerve fiber, each marked by a rounded synaptic body surrounded by vesicles. In contrast to anuran basilar papillae, efferent nerve terminals were observed in synapse with hair cells and, rarely, upon afferent fibers. The distal half of the ambystomatid papilla contained hair cells capped by tall ciliary bundles, with kinocilia that show swellings near their tips with delicate attachments to adjacent tall stereocilia. A tectorial body covers only this region of the papilla. Hair cells with shorter stereocilia, situated in the proximal half and at the papillar margins, are related only to filamentous extensions of the tectorial body. The ambystomatid basilar recess and papilla are compared to auditory end-organs in other vertebrates, and it is suggested that a basic distinction can be made between aural neuroepithelia in amniotes versus that in nonamniotic vertebrate ears.


Assuntos
Ambystomatidae/anatomia & histologia , Orelha Interna/ultraestrutura , Células Ciliadas Auditivas/ultraestrutura , Animais , Membrana Basilar/ultraestrutura , Junções Intercelulares/ultraestrutura , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Microvilosidades/ultraestrutura , Fibras Nervosas/ultraestrutura , Especificidade da Espécie , Sinapses/ultraestrutura
16.
J Morphol ; 187(2): 201-17, 1986 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-3959086

RESUMO

The surface morphology of the basilar recess and papilla was examined in 14 species of newts and salamanders selected from the five families of urodeles (Ambystomatidae, Salamandridae, Hynobiidae, Cryptobranchidae, and Amphiumidae) known to have this end-organ. In this sampling, the general organization of basilar structures is essentially similar across species investigated. The recess forms a tubular diverticulum of the proximal part of the lagena. One wall of the recess is associated with a diverticulum of the intracapsular periotic sac, and an adjacent wall is occupied by the basilar papilla. The papilla contained from as few as five hair cells in specimens of Taricha torosa to over 200 hair cells in Cryptobranchus allegheniensis. In most species, the papilla showed a morphological continuum between tall centrally or distally placed ciliary bundles and short ciliary bundles near the papillar margins. In certain species examined, tall bundles had kinocilia with swellings near their tips. Most forms showed a tendency to have groups of ciliary bundles morphologically polarized either toward or away from the saccule. In Cryptobranchus and Dicamptodon, many bundles had a random orientation. The gross and fine structural features of the basilar complex are compared in urodeles and anurans, and "generalized" features for the amphibian basilar complex are suggested. The basilar complex of Cryptobranchus is interpreted as being most generalized, representing a structural form from which most features of the basilar complex in other urodeles and anurans can be derived.


Assuntos
Orelha Interna/ultraestrutura , Células Ciliadas Auditivas/ultraestrutura , Urodelos/anatomia & histologia , Ambystomatidae , Animais , Membrana Basilar/ultraestrutura , Microscopia Eletrônica de Varredura , Salamandridae , Especificidade da Espécie
17.
Folia Biol (Praha) ; 31(6): 371-86, 1985.
Artigo em Inglês | MEDLINE | ID: mdl-3878802

RESUMO

Only very few immunological publications are based on investigations using non-mammalian vertebrates as experimental animals. Nevertheless, some important immunological problems, such as dichotomy of T and B lymphocytes or immune tolerance, were first discovered or even solved using such species. The usefulness of comparative investigations with species of different vertebrate classes is shown, referring to our own investigations of organ transplantations in the 1950s and of the regulation of the IgM antibody response in the last years.


Assuntos
Vertebrados/imunologia , Ambystomatidae/imunologia , Animais , Afinidade de Anticorpos , Carpas/imunologia , Tolerância Imunológica , Imunoglobulina G/biossíntese , Imunoglobulina G/imunologia , Imunoglobulina M/biossíntese , Imunoglobulina M/imunologia , Salamandridae/imunologia , Especificidade da Espécie , Linfócitos T/imunologia , Imunologia de Transplantes , Transplante Heterólogo , Transplante Homólogo
18.
J Neurosci ; 2(3): 339-53, 1982 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-7062113

RESUMO

Eyes were transplanted from normal axolotls to eyeless mutants, and several anatomical and physiological observations were made on the central visual centers in these animals. Some central projections were bilateral to the optic centers of the thalamus and midbrain, some traveled ipsilaterally to the same centers, and the rest grew down the spinal cord. This is similar to what has been found in eyes transplanted to normal hosts. The type of projection made in eyeless hosts correlated with the site of nerve entry into the CNS as in control hosts. Thus, the transplanted projection did not appear to be influenced by the host's optic nerves and tracts or lack of them. In spite of the transplanted optic fibers' taking abnormal paths, they made normally organized topographic maps on the host tecta. The visual and somatosensory topographic projections to the tectum were found to be in near perfect register normally, but in eyeless mutants to which rotated eyes had been transplanted, they were not. Acetylcholinesterase activity, found in the primary optic neuropil in normal animals, was greatly diminished in eyeless mutants, yet normal mutants with grafted eyes. Finally, transplantation of an eye to an eyeless mutant corrected the abnormally dark pigmentation caused by eyelessness but only in those cases of bilateral central innervation.


Assuntos
Ambystomatidae/anatomia & histologia , Olho/transplante , Mesencéfalo/anatomia & histologia , Nervo Óptico/anatomia & histologia , Córtex Somatossensorial/anatomia & histologia , Acetilcolinesterase/análise , Ambystomatidae/genética , Ambystomatidae/cirurgia , Animais , Encéfalo/anatomia & histologia , Química Encefálica , Mapeamento Encefálico , Mesencéfalo/análise , Mutação , Nervo Óptico/análise , Pigmentação , Retina/anatomia & histologia , Campos Visuais , Vias Visuais/anatomia & histologia
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