Experimental gynogenesis provides evidence of hybridogenetic reproduction in the Rana esculenta complex.

The gynogenetic offspring of the hybrid frog Rana esculenta (R. ridibunda X R. lessonae) are exclusively of the ridibunda type. This is due to the premeiotic exclusion of the lessonae genome from the hybrid's germ cells.     

Genetic control of LDH isozymes in theRana esculenta complex

Summary Studies of LDH isozymes in the European green frogs showed that the synthesis of the B subunits is controlled by 3 alleles at a single genetic locus. The genetic evidence supports the hypothesis thatRana esculenta is the hybrid ofR. lessonae x R. ridibunda.This work was supported by grants from the Schweizerischer Nationalfonds, the Georges und Antoine Claraz-Schenkung and the Karl Hescheler-Stiftung.     

A further study of LDH isozymes in theRana esculenta complex

Summary Electrophoretic analyses of LDH isozymes in the 3 types of European green frogs by using the buffer system of Williams and Reisfeld demonstrated the occurrence of 4 allelic genes coding for the B subunits. Based on the distribution of these alleles and results from dissociation and recombination of the subunits, the hybrid nature of Rana esculenta is confirmed.This study was supported in part by the Swiss National Science Foundation and the Georges-und-Antoine-Claraz-Schenkung.     

Biochemical variation in theRana esculenta complex: A new hybrid form related toRana perezi andRana ridibunda

Summary Investigations of the green frogs from western Europe for electrophoretic variations at 4 enzyme loci demonstrated a new form which must be considered as a hybrid betweenRana ridibunda andR. perezi. Biochemical evidence supports the hypothesis that its reproduction is hybridogenetic, as it is forR. esculenta.     

Genetic control of LDH isozymes in the Rana esculenta complex.

Studies of LDH isozymes in the European green frogs showed that the synthesis of the B subunits is controlled by 3 alleles at a single genetic locus. The genetic evidence supports the hypothesis that Rana esculenta is the hybrid of R. lessonae X R. ridibunda.     

Rana esculenta complex: An experimental analysis of lethality and hybridogenesis

Summary Experiments designed to analyze the lethality and hybridogenesis in the European green frog complex have yielded the following results: 1. As a rule the inter-se cross ofRana esculenta is lethal, but several crosses have produced fully viable progeny. The frequency of such break-through crosses appears to be related to parental population structure. 2. Parabiotic joining of lethal to viable embryos indicates that manifestation of the lethal effect is autonomous. There is, however, a 16–18% increase in the life span of the lethal partner. 3. Studies of LDH isozyme patterns revealed that thelessonae-specific alleles coding for the B^a and B^c subunits can be passed to the F₁ progeny from a parental female or male of theesculenta phenotype. This demonstrates that there is no total elimination of thelessonae genome in theesculenta germ cells. 4. Immunologically, offspring from the inter-se cross ofR. esculenta show a closer relationship to theridibunda than to theesculenta phenotype. Variations of antigenic protein patterns suggest the possibility of chromosomal recombination betweenlessonae andridibunda in theesculenta hybrid. These results are confirmed by two-dimensional electrophoretic analysis of proteins in the oocytes of the three frog phenotypes.This work was supported by grants from the Swiss National Science Foundation and the Georges and Antoine Claraz Schenkung.     

Biochemical variation in the Rana esculenta complex: a new hybrid form related to Rana perezi and Rana ridibunda.

Investigations of the green frogs from western Europe for electrophoretic variations at 4 enzyme loci demonstrated a new form which must be considered as a hybrid between Rana ridibunda and R. perezi. Biochemical evidence supports the hypothesis that its reproduction is hybridogenetic, as it is for R. esculenta.     

Experimental evidence of the territorial defense,hypothesis in insular Blue Tits

Many insular vertebrates have unusually high population densities and are characterized by behavioural shifts including reduced territory size and reduced situation-specific aggressiveness. Compared to their mainland counterparts, Blue Tits on the island of Corsica exhibit many traits that fit the trends observed in crowded insular populations. We demonstrate from behavioural observations in aviaries and from hormone measurements that Corsican its are less aggressive than mainland ones. These shifts, as well as changes in reproductive patterns, support the defense hypothesis.     

Origin of the differences of superficial potentials in Rana esculenta]

The spatial distributions of superficial D.C. potentials on the skin of Rana esculenta have been compared to those of the intensity of short-circuit current (S.C.C.) expressing the transcutaneous active transport of sodium ions. It has been observed that the sites of maximum D.C. potentials coincide with the localisations of maximum S.C.C. values. Moreover, superficial D.C. potentials and S.C.C. are similarly modified by the depression of metabolic activity due to lowered temperature or poisoning by dinitrophenol (DNP). It is thus proposed that the spatial distribution of the transcutaneous active transport system for sodium ions is the origin of the electric generator of superficial D.C. potentials.     

Experimental reproduction of the mechanical process of dental attrition by abrasion: paleoecological implications to fossil man]

By microscopic examination we differentiated rays appearing on dental surfaces according to the geometry of abrasive grains which produced them. Since the aspect of particules originally relied on paleoecological conditions, this new research helps us to complete our knowledge of the bolus and of fossil environment.     

Selective inhibition of reproduction in aminopterin-treated nematodes

Summary Aminopterin was applied to the free-living nematode Caenorhabditis briggsae and subsequent growth was recorded. Nematode populations, containing all developmental stages and selected juvenile stages, were exposed to the drug in both growth-promoting and non-promoting media. It is suggested that aminopterin creates a specific requirement for thymine in thymine-free medium. In otherwise growth-promoting medium, aminopterin-induced thymine deficiency will lead to progressively unbalanced growth and maturation and hence to sterility even after removal of the drug. The omission of essential amino acids from the medium during thymine starvation prevents larval growth and results in better reproduction and faster proliferation in aminopterin-free medium. The 4 juvenile stages exhibit a different response to thymine starvation created by aminopterin.     

Light and electron microscopic evidence of complex synapses (glomeruli) in oliva inferior (cat)

Zusammenfassung Mitochondrienaggregate, die durch mitochondriale Imprägnation in der Oliva inferior der Katze gefunden wurden, bestehen elektronenmikroskopisch aus mehreren dendritischen und mehreren präsynaptischen Elementen. Diese bilden multiple axodendritische Synapsen, gehören also zur Gruppe der Komplexsynapsen.

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With a grant of the Alexander-von-Humboldt-Stiftung.     

Some properties of crystalline inclusion bodies in oocytes ofRana temporaria andRana esculenta

Zusammenfassung Die drei in Oocyten vonRana temporaria undRana esculenta vorkommenden, kristallinen Einschlusskörper wurden mit Elektronenstrahl-Röntgen-Mikroanalyse und enzymatischer Verdauung am Dünnschnitt untersucht. Die hierbei erhaltenen Ergebnisse lassen auf eine unterschiedliche chemische Zusammensetzung der bis jetzt als Dotterplättchen bezeichneten Strukturen schliessen, was im Gegensatz zu bisherigen Annahmen steht.     

Seasonal variations in liver metabolism of the green frogRana esculenta (L.)

Summary Rana esculenta (L.) kept under natural conditions show almost constant b.wt in the annual cycle. Liver weight, however, has a distinct peak in October/November which is also evident in the liver index. The liver storage materials: glycogen, triglyceride and protein, show 2 distinct maxima (spring, autumn).     

Effects of acid precipitation on reproduction in birds

Summary Acidification in aquatic habitats reduces the reproductive success of both piscivorous and non piscivorous birds, mainly by reducing the food supply. Piscivorous birds find some compensation in an increased transparency of the water, non piscivorous birds in less competition for invertebrate prey by fish. Acidification in forests often has large impacts on insect populations but how this affects forest birds is unknown. Some woodpeckers and nuthatches temporarily benefit from an increase in standing dead timber. In advanced stages of forest dieback the breeding density of forest birds is very much reduced, but species of open woodland increase. Calcium deficiency reduces the reproductive output of some passerine species, but the extent of this phenomenon is unknown. Increased exposure to toxic metals has reduced the reproductive success of some lake dwelling species. It is difficult to assess the effect of acid precipitation on birds since acidification affects ecosystems in many ways, the evidence is largely correlative and reliable estimates of the population size are often lacking. Future studies should concentrate on carefully selected indicator species suitable for detailed data collection.Interested readers may also wish to refer to EXPERIENTIA's April and May 1986 issues featuring the 2-part Multi-author Review The Ecological Effects of Acid Deposition coordinated by O. Ravera.