Female alpine newts (Triturus alpestris) mate initially with males signalling fertility benefits

Gametic asymmetry implies that females invest more per gamete than males do and thus sperm is considered to be a relatively cheap resource. However, contrary to this classic view, sperm has been shown to be frequently in short supply; hence, selection favouring females that mate for fertility benefits should occur. For this reason, we determined whether males signalling fertility are preferred by female newts of the species Triturus alpestris . We performed paired female–male trials using unmated and previously inseminated females to determine potential criteria for female interest in a courting male, to establish what factors lead to successful mating and to assess the importance of female choice for direct and indirect benefits. We found that female interest in any potential mate and mating success decreased once mating had occurred. Furthermore, we detected an increase in spermatophore deposition rate and rapid spermatophore transfer in encounters that resulted in a successful mating. The results obtained indicate that female alpine newts are attracted to males showing signs of relatively high fertility and that females exhibit a decreased propensity to mate once initial sperm reserves have been acquired. Our results support the theory of initial female choice for fertility benefits.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 483–491.     

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.     

Effects of ultraviolet radiation on early larval stages of the Alpine newt, Triturus alpestris, under natural and laboratory conditions

Although Alpine newts (Triturus alpestris) are found at altitudes up to 2500 m, their larvae proved to be extremely sensitive to UV radiation when exposed in clear tapwater to natural sunlight or to comparable artificial UV-B radiation in the laboratory. The experiments revealed severe skin damages (lysis of epithelial cells) and mortality after a few days of exposure. In their natural habitats above the timberline, however, the larvae are protected by the high concentration of dissolved organic carbon in the water leading to an almost complete absorption of UV radiation within the first few centimeters of the water layer. Furthermore, when exposed to UV radiation larvae show erratic swimming activities that may carry them into protected areas. Only in very shallow natural habitats did we detect sublethal UV-like histological effects. Shallow high mountain ponds with clear water normally lack newt populations, probably as a consequence of both low temperature and the effects of UV radiation. Received: 4 October 1996 / Accepted: 7 February 1997     

Predation and competition within an assemblage of larval newts (Triturus)

The impact of crested newts (Triturus cristatus) on the smaller-bodied palmate and smooth newts (T helveticus and T vulgaris) was studied during the larval stages using a combination of field and laboratory experiments In pond enclosures T cristatus larvae had no effect on the two smaller species over the first four weeks of development By eight weeks, however. T cristatus had achieved a size advantage which enabled it to eliminate T helveticus and severely reduce T vulgaris by predation In laboratory trials under food-limited conditions, T helveticus and T vulgaris were slightly smaller when raised with T cristatus, suggesting that this predatory effect was complemented by interspecific competition during early development Predation of the smaller species started when T cristatus reached a threshold size of c 27 mm No reciprocal effects on T cristatus growth or survival were observed Although T cristatus may be a significant predator of congeneric species in natural ponds, other factors, such as differences in microhabitat selection, higher-order predator-prey interactions and the occasional desiccation of pond habitats may facilitate coexistence between the species     

Gastric evacuation rates of white perch,Morone americana,determined from laboratory and field data

Synopsis Gastric evacuation rates (R) of white perch,Morone americana, were determined in laboratory experiments and by using field data. The resulting relationship ofR and temperature (T) for white perch wasR = 0.028e^0.106T (r² = 0.98). The high r² of the regression indicates good agreement of the combined laboratory and field data. Our rate compares well with those available for other species; and especially for Eurasian perch, which has a similar thermal existence to white perch in Lake Erie.     

Chromosome 1 in crested and marbled newts (Triturus)

The heteromorphic chromosomes 1 of Triturus cristatus carnifex and T. marmoratus were studied in mitotic metaphase after staining with the Giemsa C-banding technique and with the fluorochromes, DAPI (AT-specific) and mithramycin (GC-specific). They were also examined in the lampbrush form under phase-contrast before fixation and after fixation and staining with Giemsa. Chromosomes 1 of T.c. carnifex are asynaptic and achiasmatic throughout most of their long arms. They are also heteromorphic in most of their long arms for the patterns of Giemsa and fluorochrome staining and the distribution of distinctive lampbrush loops. The heteromorphic regions correspond to the regions that are asynaptic and achiasmatic. They stain more strongly with mithramycin and more weakly with DAPI than the remainder of the chromosomes, signifying that their DNA is relatively rich in GC. The patterns of staining with Giemsa and fluorochromes and the distributions of distinctive lateral loops vary from one animal to another in the same species and even in the same population. The asynaptic and achiasmatic regions of chromosomes 1 in T. marmoratus extend throughout the whole of the long arms and well beyond the heterochromatic region. Chiasmata form only in the short arm and occasionally in the short euchromatic segment at the tip of the long arms. The staining patterns of chromosomes 1 in T. marmoratus differ from those in T.c. carnifex although, like carnifex, their DNA is relatively GC-rich. The chromosomes 1 of T. marmoratus are more submetacentric than those of T.c. carnifex. In T. marmoratus chromosome 1B is about 12% shorter than 1A. There is a short paracentric inversion heterozygosity in the long arm of chromosome 1B in T. marmoratus which probably accounts for the lack of chiasmata in the euchromatin that separates the centromere from the start of the heterochromatin. In both carnifex and marmoratus, embryos that are homomorphic for chromosome 1 arrest and die at the late tailbud stage of development. The same applies to F₁ hybrid embryos T.c. carnifex x T. marmoratus, and this has permitted identification of chromosomes 1A and 1B in both species. There is no correspondence between patterns of Giemsa or fluorochrome staining of the heteromorphic regions of chromosome 1 and any feature of the lampbrush chromosomes. However, the short euchromatic ends of the long arms of chromosomes 1 in both species are distinguished in the lampbrush form by a series of uniformly small loops of fine texture associated with very small chromomeres. The Giemsa C-staining patterns of both chromosomes 1A and 1B are different in each of the four subspecies of T. cristatus. T.c. karelinii stands out by having unusually large masses of Giemsa C-staining centromeric heterochromatin on all but 1 of its 12 chromosomes. A scheme is proposed for the evolution of chromosome 1 in T. cristatus and T. marmoratus, based on all available cytological and molecular data.     

Gastric evacuation in the young lemon shark,Negaprion brevirostris,under field conditions

Synopsis Gastric evacuation in young lemon sharks, Negaprion brevirostris, was studied in a field enclosure. Regression analysis was used to evaluate the adequacy of linear, exponential, and square root models in describing the decrease in stomach contents with time after feeding. The linear model produced the best fit and was thus used to compare gastric evacuation at the three temperatures. Gastric evacuation in young lemon sharks is considerably longer than for carnivorous teleosts but shorter than for other elasmobranchs. These differences are the result of differing energy requirements determined by the physiology and behavior of the species.     

Adaptive significance of facultative paedomorphosis in Triturus alpestris (Amphibia, Caudata): resource partitioning in an alpine lake

1. Facultative paedomorphosis is a polymorphism that has important evolutionary implications in promoting morphological differentiation and variation in habitat use. It occurs in several urodele species throughout the world. Several hypotheses based on life-history theory have been proposed to explain the wide range of habitats in which facultative paedomorphosis occurs, suggesting multifactorial causes.
2. In harsh habitats, such as mountain lakes, paedomorphosis might promote niche partitioning between morphs. This hypothesis was tested by comparing micro-habitat use and diet of two coexisting morphs in an alpine lake.
3. Paedomorphs occupied all microhabitats in the lake while metamorphs occurred only along the shoreline or at the water surface. Paedomorphic newts were frequent in deep water, where they foraged mainly on plankton. Plankton was poorly exploited by metamorphic newts, which fed mainly on terrestrial insects. Difference between morphs in microhabitat use, and consequently in the diet, were consistent in both sexes and in juveniles.
4. In adults, the mass and energy value of stomach contents did not differ between morphs, suggesting a similar food availability in the habitats occupied.
5. This study indicates habitat partitioning between morphs involving dietary differences. Specific benefits and costs of each ontogenetic pathway may allow their coexistence in this deep and fishless lake. Paedomorphosis benefits individual newts by making new food resources available and presumably reducing competition at the shore of the lake. However, the proximate causes of such an ontogenetic switch remain unclear.     

Distribution of GABA-immunoreactive neurons in the brain of adult and developing salamanders (Pleurodeles waltli,Triturus alpestris)

The distribution of GABAergic neurons in brains of the family Salamandridae (Pleurodeles waltli, Triturus alpestris) has been investigated immunohistochemically with an antibody against gamma-aminobutyric acid (GABA). In adult animals, immunoreactive neurons, fibers, and terminals are abundantly labeled. In the telencephalon, pallial areas contain fewer GABAergic neurons and fibers than basal forebrain areas. The amygdalar complex and the habenulae have a complex pattern of GABA-immunoreactivity that is especially pronounced within the neuropil. The pretectal and basal optic systems are provided with GABAergic neurons, corroborating electrophysiological results. The dorsal thalamus and parts of the torus semicircularis are almost completely devoid of GABA-immunoreactive neurons. In the torus, magnocellular neurons known to project to the contralateral counterpart are distinctly GABA-immunoreactive. During ontogeny, GABAergic neurons arise early when the first reflexive movements occur after mechanical stimulation. At stage 28, cells are labeled initially near the nucleus of the medial longitudinal fasciculus, which is the first supraspinal tract to appear in ontogeny. At stage 30 (still before hatching), GABAergic neurons are found in the pretectum, immunoreactive neurons arising in the dorsal tegmentum slightly later. Both systems are known to mediate basic reflexes in gaze stabilization. The commissura posterior is GABAergic at early stages suggesting an important functional role in homonymous inhibition between both sides. Thus in salamanders, the neurotransmitter GABA displays a complex distribution, similar to that in other vertrebrates. This pattern emerges early in ontogeny.     

Alpine newts (Triturus alpestris) as top predators in a high-altitude karst lake: daily food consumption and impact on the copepod Arctodiaptomus alpinus

1. Population dynamics and feeding ecology of adult and larval alpine newts (Triturus alpestris, Laurenti) were investigated in a high-altitude karts lake to estimate their feeding pressure on the copepod Arctodiaptomus alpinuf (Imhof). Estimates of population size for reproducing adults ranged from 666 to 864 individuals in the lake during July and August. Total abundance of larvae before the onset of ice cover varied considerably between 4400 and 25400 individuals in different years. 2. Arctodiaptomus alpinus was an important prey item for adult and larval alpine newts. During the second half of their aquatic period, adult newts moved to deeper water where the copepod reached its highest densities near the sediment. Adults and larvae exhibited no periodic feeding pattern. The feeding rhythm was more synchronized among the larvae than among the adults. 3. Daily food consumption, estimated using the Elliott & Persson (1978) model, reached 4–21 mg dry biomass in adults. The daily ration of larvae was about 7% of body dry weight in the temperature range 6-11°C. Compared to published estimates of daily food consumption in salmonid fishes, the feeding pressure of newts appears low.     

The Ectomesenchymal-Endodermal Interaction-System (EEIS) of Triturus alpestris in Tissue Culture

A piece of head neural fold tissue from behind the prospective ear region of a Triturus alpestris neurula was cultivated, together with a piece of ventrolateral pharynx endoderm from the same neurula, in hanging drop cultures. This system, referred to as the Ectomesenchymal-Endodermal Interaction-System (EEIS), offers insight into the visible processes of attachment, migration and differentiation of neural crest cells emigrating from the piece of neural fold.
The neural crest cells were not found to move preferably in the direction of the pharynx endoderm. Therefore, instead of chemotaxis, the concept of contact inhibition¹ provides a more satisfactory explanation for the distribution pattern of emigrating neural crest cells.
During culture, the neural crest cells differentiate into neuroblasts, pigment cells, myoblasts, chondroblasts and, after about 11 days, into perichondrial cells. After 6 days, a large number of neural crest cells, now called mesenchymal cells, persist without any visible differentiation throughout the culture.
Chondroblasts only develop from neural crest cells which have been in contact with the pharynx endoderm, as opposed to all other crest cells differentiating in the EEIS.     

Morphing of the phylogeographic lineages of the Balkan alpine newts (Ichthyosaura alpestris, Caudata, Salamandridae): in situ morphological diversification

Numerous alpine newt (Ichthyosaura alpestris) populations from the Balkans, representing all the previously established phylogeographic lineages, were studied for variations in various morphological characteristics (body size and shape, skull qualitative traits and number of trunk vertebrae). Here, we present a decoupling of morphological and mtDNA phylogeographic substructuring in the alpine newt on the Balkan Peninsula. In sharp contrast to other European newts (Triturus spp., Lissotriton spp.), the vast majority of morphological variation in the alpine newt is concentrated at the population level indicating an in situ morphological diversification. We found that the rate of morphological change is similar to the rate of mtDNA change. We hypothesize that the alpine newts are characterized by non-adaptive morphological evolution.     

The Ectomesenchymal-endodermal Interaction System (EEIS) of Triturus alpestris in Tissue Culture

Differentiation of visceral cartilage was studied in the Ectomesenchymal-endodermal Interaction System (EEIS), a hanging-drop culture system containing a piece of head neural fold tissue from behind the prospective ear region of a Triturus alpestris neurula together with a piece of ventrolateral pharynx endoderm from the same embryo. Cartilage cells differentiated only from those neural crest cells which have been in contact with the pharynx endoderm. Cartilage differentiation occurred neither in cultures containing neural fold or pharynx endoderm alone nor in distance cultures in which both explants were separated from each other at a greater distance than usual. However, in some critical cultures of the EEIS containing pharynx endoderm, excised more ventrally from the regular site, accumulations of ectomesenchymal cells were observed near the endoderm which were not transformed into cartilage.
The differentiation of cartilage was classified into three stages: (1) prechondroblasts (day 1 to 5), (2) chondroblasts (about day 6) and (3) chondrocytes (about day 10).
The data obtained suggested that cellular contact between the two inductively correlated tissues was a prerequisite for the transmission mechanism while mitotic cell divisions were mainly responsible for the spread of the inductive message within the responding ectomesenchymal cells.     

Thermal behaviour of A4 lactate dehydrogenase purified from the heterothermic and sympatric vertebrate species Brook lamprey (Lampetra planeri), tench (Tenca tenca), smooth (Triturus vulgaris) and alpine newt (Triturus alpestris)

1. The A4 lactate dehydrogenase isozyme was purified to homogeneity from the tissues of Brook lamprey (Lampetra planeri), tench (Tenca tenca), smooth newt (Triturus vulgaris) and alpine newt (T. alpestris). 2. These four species share their geographical distribution in the same freshwater habitats, often live together in the same station and two of them are congeneric. Steady-state kinetic investigations have shown that: 3. Km (apparent) for pyruvate vs. temperature and (apparent) product Ki (Pyruvate) and Ki (Lactate) are fairly similar among species; 4. kcat/Km decreases with temperature in the case of the newts but increases in the case of both lamprey and tench; 5. Thermostability does not correlate to preferred ambient temperature and, in particular, tench LDH starts being inactivated up to 65 degrees C. 6. Thermostability does not correlate with activation energy either; 7. No clear relationships can be demonstrated either between activation energy and conformational transitions in the molecule (these latter indicated by breaks in the Arrhenius plots) nor between activation energy and molecular flexibility, investigated by melting experiments.     

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 chromatography Dedicated to the memory of Dr. Michael Claviez     

Induction of larval diapause in the blowfly, Calliphora vicina R.-D. (Diptera, Calliphoridae) under field and laboratory conditions

Field experiments conducted in the environs of St. Petersburg (Russia) with a local population of Calliphora vicina showed that induction of larval diapause under natural conditions was significantly dependent on day lengths and temperature. The maternal photoperiodic response had a distinct threshold: the first diapausing larvae hatched from the eggs laid in the middle of August when the day length was 16 h; at shorter photoperiods, the fraction of diapausing larvae depended only on temperature. At the mean temperature of 16°C, larval diapause was rarely recorded; at 12–13°C, about 50% of the larvae entered diapause; at 7–9°C, nearly all the larvae entered diapause. These results of the field experiments agree well with the parameters of photoperiodic and thermal responses studied in the laboratory at constant temperatures and photoperiods.     

Nitrogen storage and remobilization in ash (Fraxinus excelsior) under field and laboratory conditions

 Storage and remobilization of nitrogen (N) were studied in ash trees (Fraxinus excelsior) under both field and greenhouse conditions. Experiments in the greenhouse providing ¹⁵N labelled fertilizer to the trees showed that the major quantity of N remobilized during subsequent spring was from the roots, and only a small amount from the stem. This corresponded with a loss of soluble N (proteins and low-molecular-weight compounds) from both roots and stem. On the two field sites, which differed in water availability, there was a decrease in bark N content during leaf growth, but on the dry site net N export from the bark was sustained throughout the whole vegetation period. Remobilized N was derived from soluble proteins and low-molecular-weight compounds on the moist site, which was demonstrated by the seasonal dynamics of a 56 kDa polypeptide in bark and wood. On the dry site, lower contents of soluble proteins were associated with smaller amounts of N remobilized compared to the moist site. Uptake studies of ¹⁵N labelled fertilizer indicated a higher contribution of current uptake to leaf N increment during spring at the dry site compared to the moist site. Differential N availability during the season had a decisive effect on the nitrogen storage dynamics at the two sites. Thus the influence of current N supply on N remobilization and storage as found in the greenhouse-grown plants could be verified under field conditions. Received: 28 July 1995 / Accepted: 17 July 1996