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PubMed2001

Falcaustra washingtonensis n. sp. (Nematoda: Kathlaniidae) from Ambystoma tigrinum melanostictum (Caudata: Ambystomatidae) from Washington State, USA.

Falcaustra washingtonensis n. sp. (Nematoda: Kathlaniidae) from the intestine of the salamander Ambystoma tigrinum melanostictum is described and illustrated. Falcaustra washingtonensis n. sp. represents the 14th nearctic species assigned to this genus and is distinguished from other nearctic species by the distribution pattern of caudal papillae and number of posterior muscle groups of the male: 10 pairs of sessile caudal papillae--3 pairs precloacal, 1 pair adcloacal, 6 pairs postcloacal--and 5 posterior muscle groups.

Animals↗
PubMed2005

Morphological discrimination of two genetic groups of a Japanese salamander, Hynobius naevius (Amphibia, Caudata).

Hynobius naevius, distributed on western Honshu, Shikoku, and Kyushu Islands of Japan, includes two genetically distinct groups (Groups A and B) that have never been delimited morphologically. Using specimens from the entire species range, we investigated the possibility of distinguishing these groups morphologically. Multivariate analyses of morphometric characters resulted in recognition of two groups that corresponded well to the two genetic groups. One (Group A) was characterized by larger body, compressed tail, shallower vomerine tooth series, bluish- or reddish-purple ground color, and pale-white lateral markings. In contrast, another (Group B) was characterized by smaller body, cylindrical tail, longer vomerine tooth series, reddish-brown ground color, and white lateral markings. Group A was composed of populations from the Chugoku District of Honshu and northern Kyushu, and could not be divided into subgroups, while Group B encompassed populations from the Chubu and Kinki Districts of Honshu, Shikoku and Kyushu, and was subdivided into three local subgroups that are geographically separated by marine straits. Morphometric differentiation in Group A is presumed to have been less affected by genetic factors than by other factors, such as ecological relationships with other, coexisting species. Differentiation in Group B is assumed to have been enhanced not only by genetic but also by climatological factors.

Animals↗
PubMed2005

Karyotype of a Japanese salamander Hynobius katoi and its implication on breeding ecology (Amphibia: Caudata).

Karyotype of a Japanese small salamander, Hynobius katoi, was first described. All individuals examined had 2n=58 chromosomes, consisting of nine pairs of biarmed macrochromosomes, four pairs of biarmed medium-sized chromosomes, six pairs of biarmed microchromosomes, and 10 pairs of uniarmed microchromosomes, although distinction of the second and the third groups of chromosome pairs was not clear. All pairs appeared homologous and no sexual dimorphism was found. Possession of 2n=58 chromosomes in H. katoi strongly suggests its lotic-breeding habits as was expected from the number and size of eggs and adult morphology. When compared morphology of chromosomes among lotic-breeders with 2n=58 chromosomes, metacentric nature of No. 10 seems to characterize the karyotype of H. katoi.

Animals↗
PubMedDate not supplied

[The dependence of respiratory intensity on body mass in representative Caudata and Salientia].

Experimental data indicate dependence of the respiration rate on the body mass in both caudate and ecaudate amphibians. The regression line slopes are similar in the both groups, while the a factor value is 3 times lower in the caudates than it is in ecaudates. There certain sex differences in the respiration rate which have no clear biological interpretation.

Animals↗
PubMed1988

Cytology, embryology, and evolution of the developmental arrest syndrome in newts of the genus Triturus (Caudata: Salamandridae).

We have examined embryonic development in three species (T. carnifex, T. cristatus, and T. marmoratus) of European newts of the genus Triturus (subgenus Neotriton) in which developmental arrest occurs in embryos that are homomorphic for a chromosomal heteromorphism involving chromosome 1 (Horner and Macgregor: J. Herpetol., 19:261-270, 1985). Embryonic arrest occurred during tailbud stages in all three species, but at a slightly earlier stage in T. marmoratus. Two phenotypes were identified among the arrested embryos. One of these is indistinguishable in embryonic morphology from normal embryos at all stages up to the time of arrest, but the other is characterized by a protruding yolk plug, which persists from the late gastrula/early neurula stage to the tailbud arrest stage and apparently interferes with normal morphogenesis. Evidence is presented that the two arrested phenotypes, which occur in approximately equal numbers, represent embryos that carry the two alternative homomorphic chromosome pairs of chromosome 1 heteromorphism. We conclude that developmental arrest reflects a balanced lethal heterozygosity probably resulting from an unequal exchange of genic material between the homologues of chromosome 1 which occurred in a common ancestor of the Neotriton species.

Animals↗
PubMed2006

Morphological variations in a tooth family through ontogeny in Pleurodeles waltl (Lissamphibia, Caudata).

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.

Animals↗
PubMed1984

Organization of interstitial tissue in the testis of the salamander Necturus maculosus (Caudata:Proteidae).

In Necturus maculosus the organization of the interstitial tissue varies according to the stage of spermatogenesis. Leydig cells at various stages of differentiation and myoid cells are always present in this tissue. The Leydig cells are undifferentiated at all phases of germ cell activity and only hypertrophy following spermiation and degeneration of Sertoli cells. These Leydig cells are structurally analogous to mammalian Leydig cells. They do not form part of the lamina propria of the seminiferous lobules and hence cannot be referred to as lobule-boundary cells previously described in the urodele testis (Lofts, '74). When the Leydig cells hypertrophy, numerous unmyelinated axons appear in the interstitial tissue. These axons, often devoid of Schwann-cell cytoplasm, occur in close proximity to Leydig cells. Because the levels of both Substance P and neurotensin increased in the testis of Necturus maculosus as Leydig cells differentiated, we concluded that these neural elements may regulate Leydig-cell function locally, through the release of neuropeptides.

Animals↗
PubMed1986

Morphological and fine structural features of the basilar papilla in ambystomatid salamanders (Amphibia; Caudata).

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.

Ambystomatidae↗
PubMed1986

Ontogeny of cranial ossification in the eastern newt, Notophthalmus viridescens (Caudata: Salamandridae), and its relationship to metamorphosis and neoteny.

The ontogenetic sequence of cranial osteogenesis through adulthood is described in samples of newts from completely metamorphosing and partially neotenic populations. Cranial ossification proceeds in the same sequence in both samples. Seven stages of cranial development are described on the basis of conspicuous events that occur during ontogeny. These include four larval stages, metamorphs, efts, and adults. Neotenic adults have skulls that are metamorphosed completely and indistinguishable from the skulls of non-neotenic adults. Neoteny in these newts does not involve the skull and is limited to the postmetamorphic retention of some gill structures and, thus, is termed "limited neoteny." The evolution of limited neoteny in newts as a correlated response to the inhibition of land-drive behavior is discussed.

Aging↗
PubMed1990

The cycle of follicular and interstitial cells (Leydig cells) in the testis of the marbled newt, Triturus marmoratus (Caudata, Salamandridae).

Ultrastructural examination of the marbled newt (Triturus marmoratus) testis throughout the annual cycle revealed that during the period of testicular quiescence (November-February), primordial germ cells proliferate within cords of filament-rich epithelial cells that will become follicular cells (FCs). Fibroblast-like cells surround the FCs and form the lobule-boundary interstitial cells (ICs). During the period of germ cell development from primordial germ cells to round spermatids (March-June), the FCs surrounding the developing germ cells contain scanty cytoplasm with abundant rough endoplasmic reticulum and scarce filaments. With spermatid elongation (July-August), the FC size grows, its nucleus becomes irregularly outlined, and its cytoplasm displays abundant smooth endoplasmic reticulum, residual bodies, lipid droplets, and large vacuoles. After spermatozoon release by the FCs (August-September), the adjacent ICs increase their size and transform into Leydig cells with abundant smooth endoplasmic reticulum, mitochondria with tubular cristae, and lipid droplets. During the period of testicular quiescence (November-February), the Leydig cells undergo involution, eventually developing the morphological attributes of mesenchymal cells. Intermingled among these cells, cords of filament-rich cells are observed. During this period of the cycle, spermatozoon cysts supported by FCs are present. At the beginning of the germ cell proliferation period (March), these spermatozoa are released, and the adjacent ICs undergo a transformation into Leydig cells similar to those observed in August-September. Maturation and involution of ICs occur when testosterone levels are known to be rising and falling, respectively.

Animals↗
PubMed1992

Comparative anatomy and phylogeny of the cloacae of salamanders (Amphibia: Caudata). VI. Ambystomatidae and Dicamptodontidae.

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.

Ambystomatidae↗
PubMed1997

Purification and structural characterization of insulin from the lesser siren, Siren intermedia (Amphibia: Caudata).

Insulin has been isolated from an extract of the pancreas of a salamander, the lesser siren Siren intermedia, and its primary structure was established as: A-chain, Gly-Ile-Val- Glu-Gln-Cys-Cys-His-Asn-Thr10-Cys-Ser-Leu-Tyr-Gln-Leu-Glu-Asn-Tyr- Cys20-Asn, and B-chain, Val-Pro-Asn-Lys-Pro- Leu-Cys-Gly-Ala-His10-Leu-Val-Glu-Val-Met-Tyr-Phe-Val- Cys-Gly20-Asp-Arg-Gly-Phe-Phe-Tyr-Pro-Ser-Ser-Thr 30. Although those amino acid residues considered to constitute the receptor-binding region of insulin have been retained, siren insulin contains several substitutions (Gln-->Lys at B4, Ser-->Ala at B9, Ala-->Val at B14, Leu-->Met at B15, Leu-->Phe at B17, Pro-->Ser at B28, and Lys-->Ser at B29) of amino acid residues that are conserved in insulins from species of other amphibian orders. The biological activity of siren insulin was not investigated in this study but the substitutions at B28 (involved in dimer formation) and at B14 and B17 (involved in hexamer formation) may be expected to influence conformation and therefore biological potency. The data are consistent with the view that the Sirenoidea represent an early divergence from the ancestral stock of salamanders.

Amino Acid Sequence↗
PubMed1995

MtDNA phylogeography of the California newt, Taricha torosa (Caudata, Salamandridae).

Thirty-six individuals of the California newt, Taricha torosa, representing 22 populations from throughout the range of the two currently recognized subspecies, torosa and sierrae, were examined for sequence variation in a segment (375 bp) of the mitochondrial (mt) cytochrome b gene. The maximum sequence divergence within T. torosa is about 9%. Phylogenetic analyses used the sister taxa T. rivularis and T. granulosa as outgroups. Eighteen haploid sequence types found in T. torosa were grouped by parsimony, maximum likelihood, and neighbor-joining analyses into five mitochondrial clusters: two in torosa (the northern and southern clusters) and three in sierrae (the northern, central, and southern clusters). The southern sierrae cluster apparently shared a most recent common ancestor with the northern torosa cluster. The approximate time of sequence divergence within the current species was calibrated using the known fossil record (0.8% divergence per million years or 0.01 maximum likelihood distance per million years). Phylogenetic implications of mtDNA sequence variation for evolution and biogeography of the T. torosa species complex are discussed.

Amino Acid Sequence↗