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Die jahreszeitlichen Zugmuster der häufigeren Singvogelarten auf dem Col de Bretolet im Herbst sind von Dorka (1966) dargestellt und eingehend analysiert worden. Basierend auf Beobachtungen und FängIingen legte er charakteristische Unterschiede zwischen Kurz- und Langstreckenziehern dar. Aus der Form der Zugmuster konnten in der Folge Rückschlüsse auf die Art der Steuerung der Zugaktivität gezogen werden (Berthold & Dorka 1969). Seither haben sich die Fangzahlen vom Col de Bretolet mehr als verdoppelt und die Fangzeit wurde gegen den Sommer hin ausgedehnt. Dadurch wird es einerseits möglich, bisherige Aussagen zu verfeinern ; andererseits können wesentlich mehr Arten einbezogen werden, und die bisher kaum untersuchte Phase vor der eigentlichen Zugzeit kann analysiert werden. Ein erstes Ziel dieser Arbeit ist es, die jahreszeitlichen Zugmuster nach Fänglingen für möglichst viele Arten darzustellen und damit - ohne eine eingehendere Besprechung der einzelnen Arten - eine Arbeits- und VergleichsgrundIage zu schaffen. Eine Besonderheit der Beringungsstation auf dem Col de Bretolet liegt in der subalpin-alpinen Brutvogelgemeinschaft der Umgebung. Die Durchzugsverhältnisse der Tieflandarten sind dadurch im Vergleich zu anderen Stationen in Europa, die meist im Tiefland liegen, leichter zu interpretieren. Beim Vergleich mit solchen Stationen ergeben sich bei manchen Arten augenfällige Unterschiede in der Form der Zugmuster. Solche Formunterschiede hat auch Denker (1973) beim Fitis Phylloscopus trochilus zwischen Helgoland und dem Festland gefunden. Deshalb sollen die Zugmusterformen der einzelnen Arten sowie von Bretolet und anderen Stationen miteinander verglichen werden. Dabei stehen nachbrutzeitliche Bewegungen, d. h. das Umherstreifen ohne Bindung an den Brutort zwischen dem Ende der Brutzeit und dem Beginn des Wegzuges, im Vordergrund, wobei die Lage der Fangstationen zum Herkunftsgebiet der auftretenden Arten besondere Bedeutung erhält.
Hatching asynchrony and the onset of incubation in birds revisited : when is the critical period?
(1995)
1. Birds are unique among animals in being able to influence the birthing intervals of their young through the timing of the onset incubation. However, many species hatch their young asynchronously, frequently resulting in reduced survivorship for later-hatched young. This is the Paradox of Hatching Asynchrony. 2. The Brood Reduction Hypothesis provided a resolution to the paradox by suggesting an adaptive function to the offspring mortality that results from asynchrony. Experimental tests have provided little support, and 16 alternative hypotheses have been proposed, but few have been tested. Most experimental tests have not measured important parameters such as parental effort and postfledging survival. Many have lacked adequate controls or sufficient statistical power. 3. We divide the hypotheses for hatching asynchrony into four categories based on the effects of intrinsic or extrinsic factors during a critical period of the nesting cycle which constrains reproductive success. Hatching asynchrony could be simply the consequence of the early onset of incubation during egg-laying, either as a result of physiological constraints on incubation or because parents derive fitness benefits from the protective function of early incubation. During the nestling period, hatching asynchrony could be adaptive if it allowed parents to eliminate one or more nestlings selectively, or increased parental efficiency. Alternatively, parents could manipulate the duration of the different periods of the nesting cycle to maximize benefits. 4. Because the onset of incubation generally determines hatching patterns, we encourage refocusing attention from the search for adaptive hatching patterns during the nestling period to the events surrounding the onset of incubation during egg-laying. Many factors can affect when incubation is begun, including physiology, and interactions with the environment, predators, competitors, and mates. 5. Patterns of the onset of incubation are difficult to determine and to quantify, in part because many birds begin incubating gradually, or at night. In some species, the onset of incubation varies with clutch size, but not in others. 6. The onset of incubation is the principle proximate control of hatching patterns, but other factors, such as egg size, embryonic vocalizations, and time of year may also affect hatching patterns. 7. Synchronous hatching is the primitive condition in birds, and is widespread in the lower, primarily precocial taxa. Most altricial species hatch their eggs asynchronously, although some exhibit synchrony as a secondarily derived trait. Hatching patterns show wide variation within some orders and families. 8. Patterns of the onset of incubation and hatching in a species may reflect the influence of multiplefactors. The relative importance of those factors may depend on the trade-offs associated with the potential benefits of early incubation to the survival of eggs and the potential costs to the survivor of later-hatching young associatedwith nestling size hierarchies. 9. The relative effects of multiple factors can be examined by integrating the results of empirical tests of single factors through modeling. 10. We demonstrated the use of a stochastic model by using empirical data from the House Sparrow. Results revealed the trade-offs inherent in the onset of incubation from differences in egg viability and nestling survivorship. An intermediate onset of incubation produced the greatest fledging success. 11. Other factors may be integrated into such models if they can be measured in terms of their effects on fledging success. Different factors, represented by different hypotheses, vary in how readily they may be modeled.
Habitat, food and population dynamics of the field vole Microtus agrestis (L.) in south Sweden
(1971)
The habitat, food and population dynamics of the field vole (Microtus agrestis) were studied mainly in southernmost Sweden (Scania) with a few comparisons from a northern locality. The habitats of Microtus agrestis consist mainly of successional stages, arising from abandoned cultivated fields, drained mires and felled mature forests. They were characterized botanically and classified according to moisture and time since abandonment. Capture distributions were significantly clumped, being most contagious at the lowest densities. Microdistribution was affected more by shelter than by food conditions. The weight of the stomach contents showed various skewed distributions, giving indications of the feeding behaviour of various population categories. The staple food in southernmost Sweden was various grasses, while herbs, gnss seeds, vegetative storage organs and moss were primary food items during summer, summer-autumn, winter and early summer respectively. In a northern locality herbs played a more important role in summer. Among plant species e.g. Agrostis spp., Festuca rubra, Achillea millefolium and Ranunculus spp. were often eaten, while the common Deschampsia caesjJiiosa and Charnaenerion angustifoliurn were disliked. There were clear differences between habitats but plant species belonging to the same group replaced each other in the diet. There were few differences between populatipn categories. Experiments disclosed the same preferences as found at stomach analysis. Digestibility was higher during spring than winter, that of the preferred species being highest. The digestibility was most affected by the proportions of crude protein but the changes in weight by the amounts consumed. The animals showed a decided interest in certain carbohydrates and fatty substances with differences between seasons and years. The interest in sugars was not correlated with the similar interest in bark. The probability of capture was especially low in juveniles and during winter. Trap lines and grids showed the same trappability, but, the intervals between checkings influenced the removal rate. The density changes on two distant, large, dry fields in southernmost Sweden were correlated, while a nearby isolated population in a spruce plantation fluctuated out of phase. The increases during the reproductive season were significantly lower than those expected at exponential increase. The density in various habitats did not depend on the moisture conditions. Differences in population structure and body weight in various areas were partly related to the phase of population development. However, there were also differences in the same area between habitats, which might differ in plant nutrient supply. The animals had a low energy reserve in their depot fat, which would only sustain the animals for 5-14 hours in an emergency. It was highest during midwinter but with significant depressions in April and December. Drier habitats could sustain populations of little more than 200 animals/ha over :winter and these densities were not realized in southernmost Sweden. The spring-summer density variations in a northern locality were correlated with the spruce seed supply during the following autumn-winter. A relation was assumed with the quantity or quality of previous storage tissues. In southernmost Sweden, with irregular and low-amplitude fluctuations, there was no clear relation to primary production.
Geschlechts- und Gattungsunterschiede an Metapodien und Phalangen mitteleuropäischer Wildwiederkäuer
(1968)
Zur Beurteilung der Geschechtsunterschiede und zur Bestimmung der Gattungsunterschiede wurden die Metapodien und Phalangen von im ganzen 258 Exemplaren von Cervus elaphus hippelaphus Erxleben, 1771, Dama dama dama (Linne, 1758), Capreolus capreolus capreolus (Linne, 1758), Rupicapra rupicapra rupicapra (Linne, 1758) und Capra ibex ibex Linne, 1758, ausgewertet. 93 Tiere entfielen auf Capreolus capreolus, von denen aber zur Geschlechtsunterscheidung nur 78 Tiere verwendbar waren; die restlichen 15 Tiere waren ohne Geschlechtsangabe und konnten auch nachträglich nicht bestimmt werden. Weiterhin kamen zur Untersuchung 56 Tiere von Cervus elaphus, 22 von Dama dama, 49 von Rupicapra rupicapra und 38 von Capra ibex (5. Tab. 1).
Was die Geschlechtsunterscheidung betrifft, so gilt mit Ausnahme von Capreolus capreolus die Regel, daß die Metapodien und Phalangen der Weibchen alles in allem länger und stärker sind als die der Männchen. Zur Bestimmung erwies sich die Länge des jeweiligen Knochens - an der Phalanx 3 die diagonale Sohlenlänge - als am besten geeignet. Dabei ließen sich Gesmlechtsunterschiede nicht nur in den Mittelwerten aufzeigen, sondern auch zum Teil in absolut größeren Maßen, wie das bei Dama in der Länge und bei Caprn ibex in der Breite der Fall war (s. Tab. 2-7).
Für die Unterscheidung zwischen den Gattungen waren in erster Linie Gestaltunterschiede von Bedeutung, in zweiter Linie die absoluten Maße und Indices, wovon letztere für sich allein oft schon Gattungsbestimmungen zulassen. Die Unterscheidung der hier behandelten Arten ist nahezu immer möglich, wenn man davon absieht, daß unter Siedlungsabfällen kleine, uncharakteristische Fragmente sein können. Schwierigkeiten können entstehen bei der Unterscheidung von Steinbock- sowie manchen Gemsenknochen von solchen der Gattungen Capra hircus und Ovis ades; auf sie wurde in dieser Arbeit nicht näher eingegangen.
Comparing the modern level in the biology of gastrointestinal stem cells with that achieved in the hemopoietic stem cell studies, we can say, using Till's expression (1982), that at present the "morphological phase" in the investigations of the former is continuing. Still urgent is the problem of morphological verification of presumable stem cells in colonic crypts and gastric glands. Also important is to clarify the ways of renewal of the well-differentiated but low proliferating activity endocrine cells, the chief cells of the fundic glands, and the cells of Brunner's glands. Further studies of interaction between epithelial and stromal cells are needed. The knowledge of relationships between stem cells and their differentiated "neighbors" in the niches, as well as of peculiarities of contacts between epithelial cells proper and of the cells with the basement membrane is of major importance. It is also necessary to clarify the mechanisms of the stem cells "anchoring" as well as of the disturbances of this important property during carcinogenesis. Briefly summarized below are the most essential, in our opinion, directions of the study of stem cells; some of these have already been started, whereas others can only be predicted. 1. The isolation from normal tissues of the fractions of intact cells enriched with the stem cells, with their subsequent culture. 2. The clarification of the factors governing the regulation of renewal of stem cells: specific stimulators and inhibitors of proliferation; and characterization of the receptor apparatus of stem cells, particularly for the enteropancreatic hormones. 3. The antigenic characteristic of stem cells. 4. The study of molecular peculiarities of DNA replication of clonogenic cells. 5. The molecular aspects of commitment and differentiation of stem cells. 6. The quantitative and qualitative characteristics of stem cells in the process of carcinogenesis. 7. The qualitative evaluation of the dynamics of formation and disappearance of carcinogenic DNA adducts in stem cells. 8. The clarification of interspecies features of stem cells as well as of their morphogenetic potentialities in onto- and phylogenesis. 9. The characterization of metaplastic changes in stem cells.
In 1080 samples (feathers, nesls, pellets, droppings, cloaca contents and visceral organs) collected from 92 species of free-living birds in many localities and habitats, a total of 6266 fungi was found; we identified 232 species and 112 genera of fungi (73.4 % Ascomycetes, 12.4 % Fungi imperfecti, 8.0 % Zygomycetes, 5.7 % Endomycetes, 0.3 % Oomycetes; and 0.2 % Basidiomycetes). The most common fungal genera were, in plumage, Alternaria. Cladosporium, Arthroderma, Chaetominum, Aspergillus, Penicillium and Chrllsosporium; in nests, Alternaria, Arthroderma, Penicillium, Aphanoascus and Scopulariopsis; on pellets, Penicillium, Mucor, Aspergillus, Chrysosporium and Rhizopus; in droppings, Scopulariopsis, Mucor, Aspergillus, Penicillium and Candida; from the cloaca contents, we isolated Penicillium, Candida, Aspergillus, Scopulariopsis, a. o., and from the visceral organs, Aspergillus, Penicillium, Rhodotorula, and some others. Of the fungi with a potential pathogenicity for homeotherms, we obtained, e. g., Absidia corymbifera, Aspergillus fumigatus, Candida albicans, Cryptococcus neoforrnans and Microsporum gypseum. We confirmed also the presence of several species of toxinogenic fungi (e. g., Aspergillus flavus), of the fungi with a potential pathogenicity for poikilotherms (e. g., Beauveria bassiana. Paecilomyces jarinosus, P. fumoso-roseus), and of plant parasites (Cylindrocarpon radicicola, Fusarium oxysponom and Verticillium albo-atrum). Aphanoascus reticulisporum has been described as comb. nov. (basionym: Anixiopsis: reticulispom ROUTIEN). 66 species of the fungi have not been recorded earlier in Czechoslovakia. Similarly, the occurrence of 111 species had, apparently, not been confirmed in free-living birds on a world-wide scale.
Gastropod molluscs were collected by the author between May and September 1962 from a variety of freshwater habitats in Ethiopia. Twenty-eight forms are represented in the collection of which a total of eleven have not been previously recorded from Ethiopia or have been recorded with doubt by previous authors. Two forms in each of the genera Bulinus and Ancylus appear to be new. It is considered that seven of the forms recorded from Ethiopia for the first time belong to the African component in the fauna, whereas only three are possibly of palaearctic origin. It is concluded that the wide distribution and diversity of some of the palaearctic forms justify the importance attached by Bacci (1951) to the palaearctic element in the molluscan fauna of the Ethiopian Plateau.