Celestial orientation in the marbled newt (Triturus marmoratus)

Orientation toward breeding ponds plays an important role in the seasonal movements of amphibians. In this study, adult marbled newts were tested in a circular arena to determine sensory cues used to locate breeding ponds. Animals were collected from a temporary pond situated in northern Spain, taken to the experimental site 340 m distant, and tested for orientation under a variety of conditions (i.e., orientation under a clear night sky, orientation under an overcast night sky, and orientation under a clear night sky in the presence of an altered geomagnetic field). These investigations have demonstrated that the marbled newt is able to orient using celestial cues. Animals chose a compass course in the direction of their breeding pond only when celestial cues were available. Conversely, the ambient geomagnetic field does not seem to be relevant to orientation of marbled newts since they were unable to orient themselves using the ambient geomagnetic field in the absence of celestial cues. Electronic Publication     

High aquatic niche overlap in the newts Triturus cristatus and T. marmoratus (Amphibia,Urodela)

We studied spatial niche metrics of large-bodied newts (Triturus cristatus and T. marmoratus) in three breeding ponds in western France. Adults and larvae were sampled with underwater funnel traps. Larvae were identified to the species with diagnostic microsatellite DNA markers. The distribution of adult T. cristatus and T. marmoratus across pond regions differed in one out of six cases, no differences were observed between larvae (two ponds studied). Niche overlap and niche breadth indices across resource states defined as pond regions or individual traps were high (Schoener's C: pond regions 0.60–0.98, traps 0.35–0.71; Levins' B: pond regions 0.71–0.98, traps 0.35–0.76). Adults of large-bodied newts significantly differed in resource use from small-bodied newts (T. helveticus). The results are discussed in view of the occurrence of interspecific breeding attempts, and the unpredictable ecological characteristics of newt breeding ponds.     

The effect of yellow and blue light on magnetic compass orientation in European robins, Erithacus rubecula

To analyze the wavelength dependency of magnetic compass orientation, European robins were tested during spring migration under light of various wavelengths. Under 565-nm green light (control) the birds showed excellent orientation in their migratory direction; a 120° deflection of magnetic North resulted in a corresponding shift in the birds' directional tendencies, indicating the use of the magnetic compass. Under 443-nm blue light, the robins were likewise well oriented. Under 590-nm yellow, however, oriented behavior was no longer observed, although the activity was at the same level as under blue and green light. The spectral range where magnetic orientation is possible thus differs from the range of vision, the former showing parallels to that of rhodopsin absorption. The interpretation of the abrupt change in behavior observed between 565 green to 590 yellow is unclear. There is no simple relationship between magnetoreception and the known color receptors of birds. Accepted: 17 December 1998     

Some features of the behaviour of the marbled newt Triturus marmoratus (Latreille, 1800) in captivity

The behaviour in groups of both sexes of marbled newts (Triturus marmoratus) from Sintra, Portugal, kept for a few weeks in a large aquarium, is described. Behaviour patterns described for this species and for other species in this genus were recognised. The following behaviours are described for the first time: Walk-over, Land-over, Stand-on, Show, Erect-body, Yawn, Circle, and Dig. Females seem to have a more active role in courtship than is usually considered. The behaviour frequencies for each sex were analysed using simulation statistics. Some elements usually classified as male sexual behaviours occur in both sexes and are likely to play other social roles. Received in revised form: 31 May 2001 Electronic Publication     

Alternative life-history pathways: paedomorphosis and adult fitness in European newts (Triturus vulgaris and T. alpestris)

Paedomorphs and metamorphs of the smooth newt ( Triturus vulgaris ) and alpine newt ( Triturus alpestris ) were compared with respect to body size, age structure, age at sexual maturity, survivorship, and female and male fecundity. Paedomorphs were significantly smaller than metamorphs, except for the alpine newt males. Non-significant differences between morphs in both species in terms of the life span, age of sexual maturity, survival rates and male fecundity were found. The relationships concerning female-fecundity parameters were not so straightforward. The total number of oocytes was significantly higher in smooth-newt paedomorphs, while in the alpine newt the difference was insignificant. When ovary mass was compared, significant differences appeared only in the alpine newt, in favour of metamorphic females. Oviductal egg size was similar in both morphs of T. vulgaris . The maintenance of both life-history strategies in the species studied is discussed in the light of these findings.     

The juxtaglomerular apparatus in the mesonephros of Newt (Triturus cristatus)

Summary 1)As in mammals, the juxtaglomerular apparatus of the Newt (Triturus cristatus) is composed by cells of the media of the afferent glomerular arteriole and by cells of the intermediary tubule. 2) The cells of the media of the glomerular arteriole are of two different types: granular and agranular cells. 3) The intermediary tubule is formed by dark and light cells. 4) Part of interrenal body is located close to glomerular arteriole and intermediary tubule.This work was supported by grant of Consiglio Nazionale delle Ricerche of Italy (C.N.R.) N. 115/815/04677.     

Effect of light wavelength spectrum on magnetic compass orientation in Tenebrio molitor

In many animal species, geomagnetic compass sensitivity has been demonstrated to depend on spectral composition of light to which moving animals are exposed. Besides a loss of magnetic orientation, cases of a shift in the compass direction by 90 degrees following a change in the colour of light have also been described. This hitherto unclear phenomenon can be explained either as a change in motivation or as a side effect of a light-dependent reception mechanism. Among the invertebrates, the 90 degrees shift has only been described in Drosophila. In this paper, another evidence of the phenomenon is reported. Learned compass orientation in the Tenebrio molitor was tested. If animals were trained to remember the magnetic position of a source of shortwave UV light and then tested in a circular arena in diffuse light of the same wavelength, they oriented according to the learned magnetic direction. If, however, they were tested in blue-green light after UV light training, their magnetic orientation shifted by 90 degrees CW. This result is being discussed as one of a few cases of 90 degrees shift reported to date, and as an argument corroborating the hypothesis of a close connection between photoreception and magnetoreception in insects.     

Field evidence of compass orientation in migrating juvenile grunts (Haemulidae)

Juvenile French and white grunts, Haemulon flavolineatum (Desmarest) and H. plumieri (Lacé-pède), were captured during their daily migrations between diurnal resting sites on coral patch reefs and nocturnal feeding grounds in seagrass beds. Grunts captured during morning and evening migrations were released on the route and after displacement up to 100 m or 5 km away. Grunts generally moved in the direction which would have taken them back towards their home reef or to their accustomed feeding sites, indicating that familiar landmarks are not essential for orientation. The spatial precision of migration may serve to partition the feeding area most efficiently. The timing of migrations is also very precise, and appears to be adapted to reduce the vulnerability of grunts to predation near their home reef.     

Locomotor activity rhythm and sun compass orientation in the sandhopper <Emphasis Type="Italic">Talitrus </Emphasis><Emphasis Type="Italic">saltator</Emphasis> are related

The sandhopper Talitrus saltator has an endogenous activity rhythm with a circadian periodicity. It is well known for its ability to compensate for the apparent movement of the sun during its migrations along the sea–land axis of the beach. Both chronometric mechanisms are entrained by the natural LD photoperiod. Using actographic recordings and tests of solar orientation of individuals kept under an LD 12:12 clock-shifted cycle, after 1–13 days of treatment, we demonstrate that the timing mechanism of activity rhythm and the chronometric mechanism underlying the sun compass are the same.     

Migratory orientation of European Robins is affected by the wavelength of light as well as by a magnetic pulse

The object of this study was to test the alternative hypotheses of magnetoreception by photopigments and magnetoreception based on magnetite. Migratory European Robins, Erithacus rubecula, were tested under light of different wavelengths; after these tests, they were subjected to a brief, strong magnetic pulse designed to alter the magnetization of single domain magnetite. In control tests under white light, the birds preferred the normal, seasonally appropriate migratory direction. Under 571 nm green light, they continued to be well oriented in the migratory direction, whereas under 633 nm red light, their behaviour was not different from random. The magnetic pulse had a significant effect on migratory orientation, but the response varied between individuals: some showed a persistent directional shift, while others exhibited a change in scatter; one bird was seemingly unaffected.These findings indicate a light-dependent process and, at the same time, suggest an involvement of magnetizable material in migratory orientation. They are in agreement with the model of a light-dependent compass and a magnetite-based map, even if some questions concerning the effect of the pulse remain open.     

Identification of pigment cells during early amphibian development (Triturus alpestris,Ambystoma mexicanum)

Summary The purpose of the present investigation was to provide and apply a methodological manual with which the distribution, patterning and relationship of melanophores and xanthophores can be analyzed during early amphibian development. For demonstration of the methods, which include ultrastructural, histochemical and biochemical approaches, Triturus alpestris and Ambystoma mexicanum (axolotl) embryos are used. These two species differ conspicuously in their larval pigment patterns, showing alternating melanophore bands in horizontal (T. alpestris) and vertical (axolotl) arrangements. With transmission- and scanning electron microscopy melanophores and xanthophores were distinguished by their different pigment organelles and surface structures. The presence of phenol oxidase (tyrosinase) was used to reveal externally invisible or faintly visible melanophores by applying an excess of 3,4 dihydroxy-phenylalanine (dopa). Xanthophores were made visible in fixed and living embryos by demonstrating their pterin fluorescence. In addition, pterins were analyzed by HPLC in embryos before and after pigmentation was visible.Abbreviations DOPA dihydroxy-phenylalanine - FCS fetal calf serum - FIF formaldehyde-induced fluorescence - FITC fluorescein isothiocyanate - HPLC high performance liquid chromatographyDedicated to the memory of Dr. Michael Claviez     

Thermal biology of newts (Notophthalmus viridescens) chronically infected with a naturally occurring pathogen

1.

Newts chronically infected with an Ichthyophonus-like organism selected warmer temperatures than healthy newts, consistent with prior work on behavioral fever, though the magnitude of the difference was much greater than reported in other studies.     

Putative neurotransmitters in the retinae of three urodele species (Triturus alpestris,Salamandra salamandra,Pleurodeles waltli)

Summary The immunocytochemical localization of several substances with putative neurotransmitter or modulator properties was investigated in the retinae of three urodele species. Gamma-aminobutyric acid-like immunoreactive labelling appeared in different types of amacrine and horizontal cells. In addition, labelled fibres in the optic nerve were detected. It was not possible to determine whether these fibres were ganglion-cell axons or part of an efferent projection. Endogenous serotonin was found in several populations of amacrine cells including stratified and diffuse types. Glucagon-like immunoreactivity appeared in one bistratified amacrine cell type, and neurotensin-like immunoreactivity was detected in a single monostratified amacrine cell type. Metenkephalin-like-immunoreactive labelling was rare but found in several sublaminae of the inner plexiform layer. Thus each peptide-like-immunoreactive cell type makes up a distinct and unique population of cells and probably has a special functional role in retinal processing. There are striking similarities in the peptide-like immunoreactive patterns of Triturus alpestris and Necturus maculosus whereas in Ambystomatidae the peptide-like-immunoreactive systems appear to be differently organized. This supports the hypothesis that Salamandridae and Proteidae are more closely related to each other than to the Ambystomatidae.Abbreviations GABA gamma-aminobutyric acid - GCL ganglion cell layer - Glu glucagon - HRP horseradish peroxidase - INL inner nuclear layer - IPL inner plexiform layer - IR immunoreactive or immunoreactivity - M-enk metenkephalin - Neu neurotensin - OFL optic fibre layer - ONL outer nuclear layer - OPL outer plexiform layer - Ser serotonin This work forms part of the doctoral thesis of Gaby Gläsener, Faculty of Biology, Technical University of Darmstadt, Federal Republic of Germany. Supported by a research grant from the Deutsche Forschungsgemeinschaft (Hi 306/1-1)     

Distribution of alpha7 and alpha4 nicotinic acetylcholine receptor subunits in several tissues of Triturus carnifex (Amphibia, Urodela)

The distribution of neuronal and non-neuronal mRNAs for alpha7 and alpha4 nicotinic acetylcholine receptor subunits was investigated in Triturus carnifex tissues using the in situ hybridization approach. The findings reveal a composite pattern of expression only partially overlapping for the two subunits; subunit alpha7 seems to be expressed widely throughout nervous, gastrointestinal and skin tissues, while alpha4 is present in a restricted number of cells of nervous and gastrointestinal tissue. We also found a specific pattern for each subunit; alpha7 and alpha4 associated exclusively to the epidermal glands and hypophysis, respectively; this is probably due to alternative roles that nicotinic acetylcholine receptors play in regulating physiological functions of non-neuronal amphibian tissues, rather than as mere neurotransmitters in the nervous system.     

Osmium Zinc Iodide staining of Golgi elements in oocytes of Triturus cristatus

Summary Developing oocytes of the newt Triturus cristatus were studied in order to clarify the role played by the Golgi apparatus in the formation of yolk. The cytochemical method used for this purpose was that of Maillet (1968) which employs an Osmium Zinc Iodide (OZI) complex.Previtellogenic oocytes reveal a pattern of OZI staining only after hormonal (HCG) stimulation, following which both the Golgi apparatus and the multivesicular bodies are stained.Vitellogenic oocytes taken from non-hormonally stimulated females reveal OZI deposits in a number of vesicles peripheral to the Golgi apparatus as well as within the superficial layer of the forming yolk platelets. Following hormone stimulation, many of the Golgi apparatus located in the central ooplasm of vitellogenic oocytes have all their cisternae blackened by the OZI deposits; other apparatuses, more peripherally located, remain essentially unchanged in their staining pattern. Further, a large number of OZI stained vesicles becomes visible in the vicinity of the Golgi apparatus and within the superficial layer of the forming yolk platelets.The present findings are interpreted as indicating the occurrence of fusion between Golgi derived vesicles and forming yolk platelets. It is also suggested that the vesicles in question function as carriers of Golgi produced enzymes which are presumably required to accomplish the final elaboration of the yolk material.Supported by a grant from the Consiglio Nazionale delle RicercheWe acknowledge the valuable help received from Prof. G. Mancino throughout this investigation     

Distribution of catecholaminergic and serotoninergic systems in forebrain and midbrain of the newt,Triturus alpestris (Urodela)

Summary Mapping of monoaminergic systems in the brain of the newt Triturus alpestris was achieved with antisera against (1) thyrosine hydroxylase (TH), (2) formaldehyde-conjugated dopamine (DA), and (3) formaldehyde-conjugated serotonin (5-HT). In the telencephalon, the striatum was densely innervated by a large number of 5-HT-, DA-and TH-immunoreactive (IR) fibers; IR fibers were more scattered in the amygdala, the medial and lateral forebrain bundles, and the anterior commissure. In the anterior and medial diencephalon, TH-IR perikarya contacting the cerebrospinal fluid (CSF-C perikarya) were located in the preoptic recess organ (PRO), the organum vasculosum laminae terminalis and the suprachiasmatic nucleus. Numerous TH-IR perikarya, not contacting the CSF, were present in the posterior preoptic nucleus and the ventral thalamus. At this level, DA-IR CSF-C neurons were only located in the PRO. In the posterior diencephalon, large populations of 5-HT-IR and DA-IR CSF-C perikarya were found in the paraventricular organ (PVO) and the nucleus infundibularis dorsalis (NID); the dorsal part of the NID additionally presented TH-IR CSF-C perikarya. Most regions of the diencephalon showed an intense monoaminergic innervation. In addition, numerous TH-IR, DA-IR and 5-HT-IR fibers, orginating from the anterior and posterior hypothalamic nuclei, extended ventrally and reached the median eminence and the pars intermedia of the pituitary gland. In the midbrain, TH-IR perikarya were located dorsally in the pretectal area. Ventrally, a large group of TH-IR cell bodies and some weakly stained DA-IR and 5-HT-IR neurons were observed in the posterior tuberculum. No dopaminergic system equivalent to the substantia nigra was revealed. The possible significance of the differences in the distribution of TH-IR and DA-IR neurons is discussed, with special reference to the CSF-C neurons.Abbreviations AM amygdala - CAnt commissura anterior - CH commissura hippocampi - CP commissura posterior - Ctm commissura tecti mesencephali - DH dorsal hypothalamus - DTh dorsal thalamus - FLM fasciculus longitudinalis medialis - Fsol fasciculus solitarius - H habenula - LFB lateral forebrain bundle - ME median eminence - MFB medial forebrain bundle - NID nucleus infundibularis dorsalis - nIP neuropil of nucleus interpeduncularis - NPOP nucleus preopticus posterior - NS nucleus septi - OVLT organum vasculosum laminae terminalis - PD pars distalis - Pdo dorsal pallium - PHi primordium hippocampi - PI pars intermedia - Pl lateral pallium - PN pars nervosa - PRO preoptic recess organ - Ptec pretectal area - PVO paraventricular organ - Ra nucleus raphe - Rm nucleus reticularis medius - SCO subcommisural organ - ST striatum; strm stria medullaris thalami - strt stria terminalis thalami - TM tegmentum mesencephali - TO tectum opticum - TP tuberculum posterius - trch tractus cortico-habenularis - trmp tractus mamillopeduncularis - VH ventral hypothalamus - Vm nucleus motorius nervi trigemini - VTh ventral thalamus - II optic nerve     

Use of a light-dependent magnetic compass for y-axis orientation in European common frog (Rana temporaria) tadpoles

We provide evidence for the use of a magnetic compass for y-axis orientation (i.e., orientation along the shore-deep water axis) by tadpoles of the European common frog (Rana temporaria). Furthermore, our study provides evidence for a wavelength-dependent effect of light on magnetic compass orientation in amphibians. Tadpoles trained and then tested under full-spectrum light displayed magnetic compass orientation that coincided with the trained shore-deep water axes of their training tanks. Conversely, tadpoles trained under long-wavelength (≥500 nm) light and tested under full-spectrum light, and tadpoles trained under full-spectrum light and tested under long-wavelength (≥500 nm) light, exhibited a 90° shift in magnetic compass orientation relative to the trained y-axis direction. Our results are consistent with earlier studies showing that the observed 90° shift in the direction of magnetic compass orientation under long-wavelength (≥500 nm) light is due to a direct effect of light on the underlying magnetoreception mechanism. These findings also show that wavelength-dependent effects of light do not compromise the function of the magnetic compass under a wide range of natural lighting conditions, presumably due to a large asymmetry in the relatively sensitivity of antagonistic short- and long-wavelength inputs to the light-dependent magnetic compass.