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PubMed2000

Neoteny and progenesis as two heterochronic processes involved in paedomorphosis in Triturus alpestris (Amphibia: Caudata).

Current theories on the evolution of paedomorphosis suppose that several ontogenetic pathways have appeared according to different selective pressures. The aim of this study was to find out whether two distinct processes can lead to paedomorphosis in the Alpine newt, Triturus alpestris. In this respect, we compared age structures of paedomorphic and metamorphic individuals in two newt populations where the two forms lived syntopically. Whereas paedomorphosis resulted in a slower rate of somatic development in one population, it resulted in an acceleration of sexual maturation in the other population. These processes correspond to neoteny and progenesis, respectively. These results suggest that phenotypic plasticity can result from contrasted ontogenetic pathways between two populations of the same species. They give support to models that consider gonadic development as the target of selection under different environmental pressures.

Animals↗
PubMed2005

A comparative analysis of predator-induced plasticity in larval Triturus newts.

Species that occupy similar habitats are expected to show convergent phenotypes. If habitats are defined by the presence of predators, then traits that modify vulnerability to predation, including predator-induced phenotypic plasticity, should be similar within habitats. We tested this idea using larvae of six syntopic newt species belonging to the two Triturus clades. Behavioural plasticity induced by odonate predators was strongly dissimilar between the two main clades but similar within them. Morphological plasticity was variable among species, even between one pair of closely related species. A predation experiment tested whether differences between clades could be caused by differences in body size. Size-specific vulnerability differed between newts in the small-bodied and large-bodied clades, indicating that similar predators may affect the two clades differently. The results showed both similarity and dissimilarity in predator-induced phenotypic plasticity in syntopic larval newts although theory suggests that divergence is unlikely in such ecologically similar species.

Animals↗
PubMed2005

Contemporary gene flow and the spatio-temporal genetic structure of subdivided newt populations (Triturus cristatus, T. marmoratus).

Gene flow and drift shape the distribution of neutral genetic diversity in metapopulations, but their local rates are difficult to quantify. To identify gene flow between demes as distinct from individual migration, we present a modified Bayesian method to genetically test for descendants between an immigrant and a resident in a nonmigratory life stage. Applied to a metapopulation of pond-breeding European newts (Triturus cristatus, T. marmoratus) in western France, the evidence for gene flow was usually asymmetric and, for demes of known census size (N), translated into maximally seven reproducing immigrants. Temporal sampling also enabled the joint estimation of the effective demic population size (Ne) and the immigration rate m (including nonreproductive individuals). Ne ranged between 4.1 and 19.3 individuals, Ne/N ranged between 0.05 and 0.65 and always decreased with N; m was estimated as 0.19-0.63, and was possibly biased upwards. We discuss how genotypic data can reveal fine-scale demographic processes with important microevolutionary implications.

Animals↗
PubMed1982

Selective reinnervation of skeletal muscle in the newt Triturus cristatus.

1. A study was made of the effectiveness of synapses formed by foreign and original nerves during reinnervation of skeletal muscle of the newt Triturus cristatus. The extensor cranialis nerve (e.c.n.) of the forelimb was implanted into the humeroantebrachialis muscle (biceps) which was denervated by cutting or crushing the forelimb flexor nerve (f.f.n.). 2. Although biceps became innervated by the implanted nerve, neuromuscular transmission was abnormal. The ratio of the tensions developed by biceps during single and repetitive (50 Hz) stimulation of e.c.n. was lower than either that obtained in normal biceps or during stimulation of f.f.n. after it had regenerated. Similarly, the mean quantal content of e.p.p.s evoked in biceps during stimulation of e.c.n. were lower (m = 17.1) than those evoked in normal muscles (m = 74.6) or during stimulation of the regenerated f.f.n. (m = 40.4). 3. Although the implanted e.c.n. had innervated biceps, after 2-3 months a sprout had grown out of the side of the nerve to reinnervate the extensor digitorum communis muscle (e.d.c.) of the forearm. The mean quantal content of e.p.p.s evoked in this muscle by stimulation of e.c.n. (m = 32.2) was higher than that of those e.p.p.s evoked by stimulation of e.c.n. (m = 32.2) was higher than that of those e.p.p.s evoked by stimulation of the same nerve in biceps (m = 17.1). 4. The results suggest that the synapses formed when a muscle is innervated by an inappropriate nerve are less effective than those formed when reinnervation by the correct nerve occurs. This may account for the tendency of the inappropriate synapses to regress following reinnervation by the correct nerve. In addition however, in the newt there seem to exist mechanisms which ensure that regenerating nerves reinnervate their correct muscles.

Animals↗
PubMed1968

Isolation and characterization of viruses from the kidneys of Rana pipiens with renal adenocarcinoma before and after passage in the red eft (Triturus viridescens).

Viruses were isolated from kidneys of normal and renal tumor-bearing Vermont Rana pipiens after subinoculation into red eft newts (Triturus viridescens). Organs of efts inoculated with viable cell suspensions from four of seven tumor-bearing kidneys yielded virus (LT-1, -2, -3, -4) when inoculated into TH-1 (Terrapene heart) cell culture. One tumor-bearing kidney also yielded virus (L-4) by direct inoculation into TH-1 cells. An additional isolate (L-5) was obtained from 1 of 52 normal Vermont frog kidneys inoculated directly into TH-1 cells. LT-1 was propagated with cytopathic effect (CPE) in each of 38 cell types tested, of fish, amphibian, reptilian, avian, and mammalian origin, at 23 or 30 C. LT-1 through LT-4, L-4 and L-5, and FV-1 through FV-3 each induced similar CPE in all cells tested. LT-2, however, induced CPE that progressed at a slower rate than that caused by the other isolates and produced smaller plaques (<0.8 mm) under starch gel overlay. Each of the viruses replicated to high titer in embryonated eggs incubated at 30 C. The viruses also grew in efts and adult newts, but not in bullfrog (Rana catesbeiana) tadpoles or adult leopard frogs. Tumor induction in adult leopard frogs inoculated with LT-1 was not demonstrated. Electron microscopic observations of LT-1 and LT-2 viruses revealed cytoplasmic particles, hexagonal in cross section, approximately 120 to 140 mmu in diameter, containing a dense nucleoid. LT-1 and LT-2 viruses were indistinguishable from FV-1 and Tipula iridescent virus. LT-1 was presumed to be a deoxyribonucleic acid virus on the basis of 5-bromodeoxyuridine inhibition. The isolates were ether-sensitive. On the basis of biological, physicochemical, and antigenic similarities, LT-1 through LT-4, L-4, L-5, FV-1 through FV-3, and isolates recently recovered from the bullfrog and the newt may represent strains of the same amphibian cytoplasmic virus.

Adenocarcinoma↗
PubMed1995

Connections of the posterior pallium in the crested newt, Triturus carnifex.

The connections of the posterior pallial regions were studied in the crested newt, Triturus carnifex, by means of the horseradish peroxidase technique. The tracer was injected into the lateral and medial pallia, caudal to the interventricular foramen. In addition, the connections between the posterior pallium and the infundibular hypothalamus were investigated with both horseradish peroxidase and the fluorescent dye DiI. The results show important differences between the connection patterns of the medial and lateral pallia. The lateral pallium receives inputs from the main olfactory bulb and send fibers to the contralateral hemisphere through the anterior commissure. It also shows modes extra-telencephalic connections. Conversely, the medial pallium receives direct afferent inputs from the amygdala (pars medialis) and the anterior dorsal thalamus. It is reciprocally connected to the contralateral homologue region through the hippocampal commissure, and its main efferent system is the medial forebrain bundle, which reaches the infundibular hypothalamus. The infundibulum also receives a prominent projection from the amygdala (pars lateralis). The connectivity of the posterior pallium is comparable to that reported previously for the anterior pallium, although a few differences are noted. These differences in the connectivity of the lateral pallium and the medial pallium may reflect different functional properties of these telencephalic regions.

Amygdala↗
PubMed1997

Presence of pituitary adenylate cyclase-activating polypeptide 38-immuno-like material in the brain and ovary of the female crested newt, Triturus carnifex: its involvement in the ovarian synthesis of prostaglandins and steroids.

The presence of pituitary adenylate cyclase-activating peptide (PACAP) 38-immuno-like material (PACAP 38-IL) in the brain and ovary of the crested newt, Triturus carnifex, and its action on ovarian steroidogenesis and prostaglandin synthesis were evaluated. The HPLC, brain and ovary extract peaks that eluted like PACAP 38 were considered PACAP 38-like material. The concentrations of PACAP 38-II in the HPLC extracts were measured by RIA. T. carnifex ovary was incubated with PACAP 38, brain and ovary PACAP 38-IL, and inhibitors of cyclooxygenase (COX), adenylate cyclase (AC) and phospholipase C (PLC) for 30 and 60 min. PACAI 38, and brain and ovary PACAP 38-IL increased prostaglandin E2 (PGE2) (30 and 60 min), and progesterone and corticosterone (60 min), but decreased oestradiol-17 beta (60 min). COX and PLC inhibitors counteracted the increases in PGE2, progesterone and corticosterone and the decrease in oestradiol-17 beta, and the AC, inhibitor also counteracted them except for PGE2. These results suggest that PACAP 38-IL, present in T. carnifex brain and ovary, acts on PLC, inducing the increase of PGE2 which, in turn, acting on AC, induces increases in progesterone and corticosterone and a decrease in oestradiol-17 beta.

Adenosine↗
PubMed1990

Demonstration of sensory-motor innervation of postmetamorphic forelimb regenerates of Triturus alpestris (Urodela) on cryotome serial sections using horseradish peroxidase.

A method has been developed to obtain horseradish peroxidase-treated serial sections containing spinal cord as well as bilateral ventral and dorsal roots, dorsal root ganglia and spinal nerves. Young postmetamorphic newts (Triturus alpestris) served as experimental animals. After cryotome cross sectioning the forelimb region of the trunk, slices 80 microns in thickness were mounted serially with up to 15 sections per slide. This facilitated subsequent staining manipulations and made partial loss of sections less likely.

Animals↗
PubMed1992

Characterisation of secondary spermatocytes in the marbled newt (Triturus marmoratus).

Secondary spermatocytes in the marbled newt (Triturus marmoratus) were identified by means of cytophotometric quantification of nuclear DNA in the testicular lobules containing primary spermatocytes in advanced stages of the first meiotic division (from pachytene onwards) and newly formed spermatids. The nucleus of secondary spermatocytes has an intermediate size between that of primary spermatocytes and round spermatids and was characterised by the presence of abundant masses of dense chromatin and the absence of a nucleolus. At the prophase the chromatin masses were located at the periphery of the nucleus. The ultrastructural study revealed that the nuclear envelope displayed blebs and that the cytoplasm was very similar to that of primary spermatocytes including the presence of smooth endoplasmic reticulum whorls, multiple small dictyosomes, and a proacrosomal-like granule near the nucleus. This granule stained weakly with aqueous PTA and was observed in about 6% of secondary spermatocytes. Many of the mitochondria were grouped beneath the plasma membrane. Approximately 2% of these cells presented an axoneme which was not associated with other flagellar components.

Animals↗
PubMed1989

Differentiation of liquor contacting neurons in the regenerating spinal cord of the newt Triturus.

This paper reports a detailed electron microscopic study of the ventricular cells in the growing spinal cord during the first two months of tail regeneration in Triturus vulgaris and T. cristatus. In the proliferating ependyma some cells undergo a neural differentiation in order to produce "Cerebro-Spinal-Fluid-Contacting-Neurons (CSFCNs). These round or pear-like cells store dense core vesicles, 80-100 nm in diameter, and show less electron-density than ependymal elements. The stereociliar apparatus is the last cytological differentiation of these elements and after two months of regeneration, synapse-like endings were occasionally found.

Animals↗
PubMed1975

Incomplete antibodies and immunoglobulin characterization in adult urodeles, Pleurodeles waltlii Michah. and Triturus alpestris Laur.

Humoral immunoglobulin synthesis has been studied in two adult urodeles, Pleurodeles waltlii Michah. and Triturus alpestris Laur. following SRBC immunization. The specific antibody response is detected after a long period of immunization and is due exclusively to 'incomplete' antibodies which are unable to induce agglutination. The antibody titre is essentially dependent on the number of stimulations rather than on the dose or nature of the antigen (papainized or normal erythrocytes). Antibodies are detected in only 50 per cent of the immunized animals, 50 per cent never respond. This suggests that the latter group does not possess the genetic equipment (Ir genes) to recognize the antigenic determinants and to synthesize the corresponding antibodies. The sedimentation coefficient of the synthesized immunoglobulins was investigated by sucrose density gradient centrifugation and their characterization was carried out by starch and polyacrylamide gel electrophoresis. With this peculiar antigen even after a booster injection, only one class of immunoglobulin, an 18-2S IgM could be detected.

Animals↗
PubMed1982

Effect of hypophysectomy and starvation on the fine structure of vitellogenic oocytes in the newt, Triturus pyrrhogaster (Laur).

Hypophysectomy and starvation in Triturus pyrrhogaster result in a similar ultrastructural pattern of follicular atresia. The first detectable change in the oocytes is decrease in the size and number of microvilli. Subsequently the yolk precursor bodies (YPB) disappear from the micropinocytotic vesicles and the mitochondria degenerate. Finally the yolk platelets undergo decomposition. The smaller yolk platelets disintegrate by granulation, vacuolation and lobule formation. The larger platelets, after losing their superficial layer and the inner crystalline lattice, are surrounded by a laminated membrane complex. The pattern of yolk breakdown is comparable to that during development. A rather delayed effect is observed on the nucleolus of the oocytes. Pigment granules seem to play an important role in the proteolysis of the yolk.

Animals↗
PubMed1999

Ultrastructure and lectin cytochemistry of the cloacal ventral glands in the male newt Triturus marmoratus marmoratus.

Ventral glands are found in the cloacal walls of male urodele amphibians except for sirenids. These glands are mucous, and secrete substances that will form part of the spermatophore used in transfer of sperm during fertilization. Ventral glands are formed by secretory and ductal portions; both possess epithelial and myoepithelial cells with different characteristics. Urodeles have cyclic reproduction, and cloacal ventral glands show seasonal differences with electron microscopy. The glycoproteins secreted by these glands have been studied by means of lectin histochemistry. The labeling was detected mainly in the nuclei, rough endoplasmic reticulum, Golgi complex, and cytosol. Secretory granules in these glands are composed by mucous glycoproteins that bind PNA lectin (which binds galactose) and SBA and HPA lectins (N-acetylgalactosamine), UEA-I (fucose), and LcA (glucose and/or mannose). These findings suggest that the mucins secreted by ventral glands contain both N- and O-linked oligosaccharides. Ventral glands secrete higher quantity and more diverse mucous substances in the reproductive period, as confirmed by lectin-histochemical reactions. Based on these results, the major similarity between ventral cloacal glands and accessory mammalian glands, can be established with bulbourethral glands.

Animals↗