Die Entwicklung von Acanthamoeba castellanii zur Cyste mit und ohne Veränderung des Genaktivitätsmusters*

Die Hemmung der mitochondrialen DNS-Snythese von Acanthamoeba castellanii der logarithmischen Wachstumsphase durch Äthidiumbromid induziert die stationäre Wachstumsphase, in deren Verlauf Cysten gebildet werden. Diese Cystenbildung ist, im Gegensatz zu der durch Sauerstoff oder Nahrungsmangel hervorgerufenen, nicht von einer in DNS-RNS-Hybridisierungen nachweisbaren Synthese qualitativ neuer RNS-Arten begleitet. Wahrend der durch Äthidiumbromid, Sauerstoff- und Nahrungsmangel induzierten stationären Wachstumsphase und Encystierung findet eine starke Reduktion des [₃H]Uridin-Einbaus in die RNS statt; davon ist die ribosomale stärker als die niedermolekulare RNS betroffen. In der durch Äthidiumbromid induzierten stationären Wachstumsphase und in der späten 1WP sind in der RNS weniger DNS-ähnliche RNS-Arten vorhanden als in der frühen logarithmischen Wachstumsphase.     

Introgressive Hybridisation,Sippenbildung und Vegetationsänderung

Introgressive hybridization is a phenomenon, which takes place in natural conditions, on vast territories, during thousands of years and connected with paleogeographic events. The introgressive hybridization usually involves not only certain pairs of species in a definite region, but many species. Species, pertaining to different specific rows or different sections of genus enter into the introgression. Hybrid forms, having arisen in the process of introgression are of low stability. Change of climatic conditions leads to absorption of hybrid by those ancester-parents, for which this change is most favourable. The absorption by one species edificator of his own hybrid populations reflects the displacement of one vicaring formation by another. The introgressive hybridization, which has been occuring during the tertiary time and has lead to speciation nowadays presented in classification by sectional level (Picea sect. Omorika, Larix sect. Multiseriales), has not created new stable lines of development. Introgressive hybridization in cases known, as well as in examples of Picea and Larix has not opened and is not opening new evolutional perspectives.     

Phylogeny and Reclassification of Hemistasia phaeocysticola (Scherffel) Elbrächter & Schnepf, 1996

Hemistasia phaeocysticola is a marine flagellate that preys on diatoms and dinoflagellates among others. Although its morphology and ultrastructure were previously observed and characterized, its phylogenetic position has not been analyzed using molecular sequence data. This flagellate was classified as a kinetoplastid on the basis of the presence of a kinetoplast in the mitochondrion. However, several morphological characteristics similar to those of diplonemids, a sister group of kinetoplastids, have also been noted. Herein, we report that H. phaeocysticola branches within the diplonemid clade in the phylogenetic tree reconstructed by analyzing 18S rRNA gene sequences. Its systematic placement based on this finding is also discussed.     

Zur Funktion von Warnfarben: Die Reaktion junger Stare auf wespenähnlich schwarz-gelbe Attrappen

Social regulation of developmental rate of the African cichlid fish, Haplochromis bur-toni, was studied experimentally. Broods were raised under three different social conditions: total isolation, with no visual, physical or chemical contact with siblings; physical isolation, with no physical or chemical contact with siblings; and in social groups. Development of behavior and color patterns were observed in fish from 2 to 14 weeks of age. Males were sacrificed at 4-week intervals to measure growth and maturation state. Results showed that developmental rate is influenced by the social environment. Males with no territories (raised in groups) grew and matured more slowly than those in all other conditions. These males were not prevented from maturing but both the rate and phenotypic expression of maturation were inhibited.     

Temperaturabhängiges Putzen bei Sammelwespen

The influence of temperature on the preening of foraging wasps (Paravespula vulgaris) collecting sucrose solution at an artificial food source is described. The temperature has an influence on the number of preening movements performed per unit time (= rate of preening) as well as on the spatial distribution of the preening movements. The rate of preening as a function of the temperature is explained in a quantitative manner using a diagram, which corresponds to the disinhibition hypothesis for displacement activities. This also holds true for the honeybee. The degree of disinhibition of the preening tendency does not determine the spatial distribution of the preening movements.