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At least 289 records · Page 16Linked to original sources
PubMed1996

Heteromorphic sex chromosomes in Eupsophus insularis (Amphibia: Anura: Leptodactylidae).

The chromosomes of the Chilean frog Eupsophus insularis are described for the first time. This species has a chromosome number of 2n = 30, and based on the karyotype it is concluded that E. insularis is closely related to E. migueli. E. insularis has an XX/XY system of sex determination, and pericentromeric constitutive heterochromatin is present in all chromosomes except in the Y chromosome. It is postulated that the Y chromosome is derived from a small ancestral metacentric chromosome that lost its heterochromatic segment.

Animals↗
PubMed2003

A skeletochronological study of growth, longevity, and age at sexual maturity in a population of Rana latastei (Amphibia, Anura).

Longevity and age at sexual maturity in an Italian population of Rana latastei were studied by skeletochronology performed on the phalanges. Frogs collected in 1998 and 1999 by drift fences and pitfall traps were marked by toe-clipping. After marking, individuals were released and the cut phalanges were processed for skeletochronological analysis. The maximum age so far recorded was 3 years in males and 4 years in females. The smallest male and female that were sexually mature on the basis of histological analysis of the gonads were 36 and 35 mm snout vent length (SVL), respectively. In both sexes, most individuals were estimated to breed shortly after emergence from their first overwintering. Among the European Brown Frogs, Rana latastei appears to be one of the shortest-lived and one of the first to reach sexual maturity.

Animals↗
PubMed2004

A relict trematosauroid (Amphibia: Temnospondyli) from the Middle Jurassic of the Junggar Basin (NW China).

A temnospondyl ilium from the uppermost Toutunhe Formation (Middle Jurassic, Callovian) of the southern Junggar Basin is described. Among the known temnospondyls it is very unusual in morphology because of its very long and slender shaft. It compares closely only to the ilium of one of the latest known trematosaurids from the Ladinian of southern Germany. The Toutunhe Formation has also yielded vertebrae and skull fragments of temnospondyls which belong to the brachyopid Gobiops from the Upper Jurassic of Mongolia. Brachyopoid ilia do not, however, display a morphology similar to that of the new specimen. It is therefore concluded that this specimen represents a second taxon of temnospondyl from the Toutunhe Formation, which probably represents the latest surviving trematosauroid. The Trematosauroidea, which was hitherto exclusively known from the Lower to early Upper Triassic, therefore joins the Brachyopoidea--and possibly the Capitosauroidea --as another group of temnospondyls which survived the end--Triassic mass extinction.

Amphibians↗
PubMed2006

Serum protein profile and blood cell counts in adult toads Bufo arenarum(Amphibia: Anura: Bufonidae): effects of sublethal lead acetate.

Lead is a multiple-source pollutant, well known for its toxicity, of great risk both for the environment and human health. The main target organs of lead are the hematopoietic, nervous, and renal systems; there are also reports in support of its impairment effects on the reproductive and immune systems. It is well known that most of the metal is accumulated in the blood cells and that many of the deleterious effects are related to its circulating concentrations. These adverse effects have been described not only in humans but also in a number of other vertebrates such as fish and birds. The purpose of the present work was to evaluate the effects of weekly administration of sublethal Pb (as acetate, 50 mg x kg(-1)) during 6 weeks on the profile of the serum proteins and blood cell counts of the adult South American toad, Bufo arenarum (Anura: Bufonidae). The electrophoretic patterns of serum proteins pointed out the presence of four fractions; the metal provoked a significant decrease in both total proteins and albumin fraction; among the globulin fractions, the G3 resulted augmented. These findings may be related to the impact of lead on the toads' hepatic cells and immune system. The number of total red blood cells (RBC) showed a tendency to decrease after the injections of the metal, whereas the number of white blood cells (WBC) increased significantly; the differential leukocyte counts showed a statistically significant increase in the absolute number and in the relative percentage of blast-like cells. The decrease in RBC was attributed to the negative impact of the metals on the hemoglobin synthesis. The increasing of the WBC counts may be interpreted as a consequence of the induction of proliferation of pluripotential hematopoietic cells.

Animals↗
PubMed2001

Temporal selectivity by single neurons in the torus semicircularis of Batrachyla antartandica (Amphibia: Leptodactylidae).

We investigated the response selectivities of single auditory neurons in the torus semicircularis of Batrachyla antartandica (a leptodactylid from southern Chile) to synthetic stimuli having diverse temporal structures. The advertisement call for this species is characterized by a long sequence of brief sound pulses having a dominant frequency of about 2000 Hz. We constructed five different series of synthetic stimuli in which the following acoustic parameters were systematically modified, one at a time: pulse rate, pulse duration, pulse rise time, pulse fall time, and train duration. The carrier frequency of these stimuli was fixed at the characteristic frequency of the units under study (n=44). Response patterns of TS units to these synthetic call variants revealed different degrees of selectivity for each of the temporal variables. A substantial number of neurons showed preference for pulse rates below 2 pulses s(-1), approximating the values found in natural advertisement calls. Tonic neurons generally showed preferences for long pulse durations, long rise and fall times, and long train durations. In contrast, phasic and phasic-burst neurons preferred stimuli with short duration, short rise and fall times and short train durations.

Acoustic Stimulation↗
PubMed1997

Temporal selectivity for complex signals by single neurons in the torus semicircularis of Pleurodema thaul (Amphibia:Leptodactylidae).

Responses of auditory neurons in the torus semicircularis (TS) of Pleurodema thaul, a leptodactylid from Chile, to synthetic stimuli having diverse temporal patterns and to digitized advertisement calls of P. thaul and three sympatric species, were recorded to investigate their temporal response selectivities. The advertisement call of this species consists of a long sequence of sound pulses (a pulse-amplitude-modulated, or PAM, signal) having a dominant frequency of about 2000 Hz. Each of the sound pulses contains intra-pulse sinusoidal-amplitude-modulations (SAMs). Synthetic stimuli consisted of six series in which the following acoustic parameters were systematically modified, one at a time: PAM rate, pulse duration, number of pulses, and intra-pulse SAM rate. The carrier frequency of these stimuli was set at the characteristic frequency (CF) of the isolated units (n = 47). Response patterns of TS units to synthetic call variants reveal different degrees of selectivities for each of the temporal variables, with populations of neurons responding maximally to specific values found in the advertisement call of this species. These selectivities are mainly shaped by neuronal responsiveness to the overall sound energy of the stimulus and by the inability of neurons to discharge to short inter-pulse gaps.

Acoustic Stimulation↗
PubMed2002

The morphology of the rostral notochord in embryos of Ichthyophis kohtaoensis (Amphibia, Gymnophiona) is comparable to that of higher vertebrates.

The rostral notochord plays an important role in the head development of vertebrates. Yet, in contrast to trunk notochord, the course and behavior of the head notochord shows species-specific variations. To analyze normal and abnormal development in the head region, knowledge of the normal behavior of the rostral notochord is a prerequisite. Therefore, we studied the rostral notochord of Ichthyophis kohtaoensis, not only in anatomical view a relatively unknown order of Gymnophiona, in embryos of the stages B, C, D, E according to Himstedt (1996) or stages 21, 22, 26, 31 according to Dünker et al. (2000). We described the course, form, and structure of this part of the notochord and compared it with morphological features and variations of the notochord in existing studies of higher vertebrates (Barteczko and Jacob 1999). We found that the rostral notochord of this oviparous Gymnophiona from Thailand is quite similar to that of higher vertebrates: its tendency to elongate directly in a rostral direction is prevented by the adenohypophysis as a barrier; at stage B the neurohypophysis/infundibulum takes the role of a hindrance. Light microscopic results, laser scanning micrographs, and plastic reconstructions based on serial sections showed unequivocally in stages B-E the effects resulting from this hindrance: buckling, variations in volume, screw-like torsions, undulations, deviations, and splintering. The notochord was found to lie dorsal to the developing cartilaginous basicranium. The tendency to press the dura towards the brain was conspicuous. The formation of a bursa pharyngea was likewise observed; the predisposition of several such structures exist. We suggest that the vertebrate phenotype with the appearance of preaxial structures, in contrast to the chordata phenotype, correlate with the formation of a hypophysis. Experiments have yet to prove this hypothesis.

Amphibians↗
PubMed2006

The adrenal gland of newt Triturus carnifex (Amphibia, Urodela) following in vivo betamethasone administration.

The response of the adrenal gland of Triturus carnifex to betamethasone administration was studied; the effects were evaluated by examination of the ultrastructural morphological features of the tissues as well as the serum levels of aldosterone, corticosterone, norepinephrine and epinephrine. In March and June, betamethasone significantly decreased the serum levels of aldosterone and corticosterone and the lipid droplet content in the steroidogenic cells. Moreover, betamethasone influenced the chromaffin tissue, enhancing in March (when the chromaffin cells produce norepinephrine and epinephrine in almost equal quantities) epinephrine serum levels and the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells. In June, (when the chromaffin cells contain almost exclusively norepinephrine granules) betamethasone administration raised norepinephrine serum levels, whereas a decrease in the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells was found. Finally, betamethasone administration did not evoke in June any increase in the mean number of epinephrine granules in the chromaffin cells and/or in epinephrine serum levels, as would be expected if phenyletanolamine-N-methyl transferase (PNMT) enzyme, converting norepinephrine into epinephrine, were activated by corticosteroids. The results of this study showed that betamethasone decreased aldosterone and corticosterone serum levels and enhanced catecholamine serum concentrations. Moreover, the present results suggest that a stimulatory role of glucocorticoids on PNMT enzyme may be ruled out.

Adrenal Glands↗
PubMed1998

Colocalization of serotonin and GABA in retinal neurons of Ichthyophis kohtaoensis (amphibia; Gymnophiona).

Ichthyophis kohtaoensis, a member of the limbless Gymnophiona, has a specialized subterranean burrowing mode of life and a predominantly olfactory-guided orientation. The only visually guided behavior seems to be negative phototaxis. As these animals possess extremely small eyes (only 540 microm in diameter in adults), functional investigations of single retinal cells by electrophysiological methods have so far failed. Therefore, the content and distribution of retinal transmitters have been investigated as indications of a functioning sense organ in an animal that is supposed to be blind. Previous immunohistochemical investigation of the retinal transmitter system revealed immunoreactivity for gamma-aminobutyric acid (GABA), serotonin, dopamine and tyrosine hydroxylase, the rate-limiting enzyme in the catecholamine synthetic pathway. The present studies have been performed in order to determine a possible colocalization of serotonin and GABA in retinal neurons of the caecilian retina. Therefore retinal cryostat sections of various developmental stages have been investigated by the indirect fluorescence method. In single-label preparations, serotonin is localized to cells in the inner nuclear layer and the ganglion cell layer. GABA immunocytochemistry labels a variety of cell types in the inner nuclear layer as well as cell bodies in the ganglion cell layer. In double-label preparations, some of the serotonergic cells are found to express GABA immunoreactivity and some GABAergic neurons also label for serotonin immunocytochemistry. Thus, despite the fact that caecilians mainly rely on olfaction and are believed to have a reduced visual system, their retina exhibits a surprisingly "normal" distribution of neurotransmitters and neuromodulators, also typical of other anamniotes with a well-developed visual system, including the partial colocalization of serotonin and GABA at all developmental stages of I. kohtaoensis. These results indicate that a functional system that is under no strong selective pressure obviously has a long evolutionary persistence irrespective of its need for use.

Amphibians↗
PubMed1999

Serotonergic neurons and processes in the adult and developing retina of Ichthyophis kohtaoensis (Amphibia; Gymnophiona).

Ichthyophis kohtaoensis is a tropical, limbless amphibian species with extremely small eyes (540 microm in adults). Adapted to a subterranean, burrowing mode of life, orientation and prey capture are predominantly guided by olfaction. The only visually guided behavior seems to be negative phototaxis. As electrophysiological single cell recordings have so far failed, immunohistochemical transmitter studies are a starting-point for a functional investigation of the visual system of this group of amphibians. In the present study, the organization and development of the serotonergic system have been examined in the retinae of embryonic, larval and adult I. kohtaoensis, using an antiserum against serotonin. Labeled somata are situated in the inner nuclear layer, presumably representing amacrine cells, and in the ganglion cell layer. However, some immunoreactive cells are located in the middle of the inner nuclear layer that send processes to both plexiform layers, probably representing bipolar cells. An additional type of immunoreactive soma, situated in the inner plexiform layer, have been found only in retinae of embryonic stages. Varicose serotonergic fibers form a diffuse plexus that covers the whole inner plexiform layer. Immunolabeled fibers can occasionally be demonstrated in the optic nerve head. During retinal development, the distribution and number of transmitter-expressing cells changes but no general reduction of the visual system is detectable. Adult stages still have a serotonergic system comparable to amphibians with a well-developed visually guided behavior indicating that the eyes of I. kohtaoensis although being of minor importance in a subterranean habitat, retain all the elements of functioning sense organs.

Amphibians↗
PubMed2000

Cutaneous glands in the Australian hylid Litoria caerulea (Amphibia, Hylidae).

Ultrastructure of cutaneous glands is described in the Australian hylid Litoria caerulea. Three main types of glands could be distinguished in both ventral and dorsal skin: mucous, serous or granular, and lipid glands. Both mucous, and to some extent, serous glands show a PAS-positive reaction. Some of the granular-serous glands react to lipid staining. In addition, a very large gland confined to the dorsal skin of the head reacts to lipid staining. Apparently more than one type of dermal gland is involved in lipid secretion. The subject of skin lipid secretion is discussed in relation to the ecophysiological adaptations of this xeric-inhabiting frog.

Animals↗
PubMed1997

Distribution of vasotocin- and mesotocin-like immunoreactivities in the brain of typhlonectes compressicauda (Amphibia, gymnophiona): further assessment of primitive and derived traits of amphibian neuropeptidergic systems.

To further assess primitive and derived conditions, we have studied the vasotocinergic (AVT) and mesotocinergic (MST) systems by immmunohistochemistry in the brain of Typhlonectes compressicauda. This species belongs to a separate order of amphibians which differs in several morphological and behavioral aspects from anurans and urodeles which have been studied previously. Nevertheless, the vasotocinergic and mesotocinergic systems of T. compressicauda are largely comparable to those of other amphibians. Apart from a well-developed hypothalamo-hypophyseal system, extrahypothalamic AVT-and MST-immunoreactive groups of cells and extensive networks of fibers were found. A major difference, however, is that neuropeptidergic cells in the caudal hypothalamus and the midbrain tegmentum of T. compressicauda contain MST, whereas those in corresponding locations contain AVT in anurans and urodeles. This suggests that certain neuropeptidergic cell groups in the gymnophionan brain have switched from AVT to MST gene expression, and, thereby, offers a new view on the functional significance of these neuropeptidergic systems.

Amphibians↗
PubMed1997

Development and organization of the retinal dopaminergic system of Ichthyophis kohtaoensis (Amphibia; Gymnophiona).

Ichthyophis kohtaoensis, a member of the limbless Gymnophiona, has a specialized subterranean burrowing mode of life and a predominantly olfactory-guided orientation. The only visually guided behavior seems to be negative phototaxis. As these animals possess extremely small eyes (only 540 microm in diameter in adults), functional investigations of single retinal cells by electrophysiological methods have so far failed. Therefore, the content and distribution of retinal transmitters have been investigated as indications for a functioning sense organ in an animal that is supposed to be blind. In this study, the organization and development of the dopaminergic system have been examined in the retinae of embryonic, larval, and adult I. kohtaoensis, by using an antiserum against tyrosine hydroxylase, the rate-limiting enzyme in the catecholamine synthetic pathway, and an antiserum against dopamine itself. Labeled somata are situated in the inner nuclear layer and in the ganglion cell layer. Dopamine-positive fibers form a dense diffuse plexus, that covers the whole inner plexiform layer, whereas tyrosine hydroxylase-immunoreactive processes show a tendency to arborize in a stratified manner. Tyrosine-hydroxylase-immunolabeled fibers can occasionally be observed in the optic nerve head of larval stages. During ontogenesis and larval development, the distribution of transmitter-expressing cells changes and their number decreases, but no general degeneration of the visual system is detectable. Adult Ichthyophis still have retinal transmitters, indicating that the eyes, although obviously playing a minor role in a subterranean ecological niche, retain all the elements of functioning sense organs.

Amphibians↗
PubMed1998

A double-label analysis demonstrating the partial coexistence of tyrosine hydroxylase and GABA in retinal neurons of ichthyophis kohtaoensis (Amphibia; gymnophiona)

Ichthyophis kohtaoensis is a limbless amphibian species with a subterranean mode of life and a predominantly olfactorily guided orientation. The only visually guided behavior seems to be negative phototaxis. As these animals possess extremely small eyes (only 540 microm in diameter in adults), functional investigations of the retina by electrophysiological single cell recordings have so far failed. Therefore, immunohistochemical transmitter studies constitute a starting point for a functional investigation of the caecilian retina. Previous immunohistochemical examinations have revealed immunoreactivity for gamma-aminobutyric acid (GABA), serotonin, dopamine and tyrosine hydroxylase (TH). The double-labeling experiments of the present study show that some TH-immunoreactive cells also express GABA-like immunoreactivity and some GABAergic neurons also label for TH immunocytochemistry, revealing a partial coexistence of TH and GABA in caecilian retinal neurons. On the one hand, these results contrast with previous reports, stating that in amphibians GABA-immunoreactive cells constitute a separate population from TH-positive neurons and colocalization is restricted to higher vertebrates. On the other hand, the findings indicate that a functional system which is under no strong selective pressure obviously has a long evolutionary persistence irrespective of its need for use.

Journal Article↗