Induction of Temperature Sensitivity in Paramecium aurelia by Nitrosoguanidine*

Paramecium aurelia cells were exposed to N-methyl-N-nitroso-N′-nitroguanidine for periods of 15–30 min. The lethality in homozygous clones derived from treated cells depends on the time of treatment within the cell cycle. Exposures at interfission ages 0.04, 0.40, and 0.80 were tested yielding lethalities of 12.5, 44 and 2%, respectively. These results correlate with the period of DNA synthesis in the micronuclei. A temperature sensitive mutant has been found which cannot live at 31 C but divides at ～1 fission per day at 19 and 25 C. The rise in temperature from 19–25 C does not significantly change the fission rate whereas in normal cells it would be doubled. Genetic analysis shows that this mutation is caused by a single recessive gene.     

Patterns of abundance, distribution, and alary polymorphism among the salt marsh Delphacidae (Homoptera: Fulgoroidea) of Northwest Florida

Abstract. 1. The species of Delphacidae captured in nearly 16000 sweeps of salt marsh vegetation in Northwest Florida, U.S.A., are examined. Individuals belonging to fourteen species were captured during the 15-month study, a somewhat larger number than is found in most locations.
2. Abundances ranged from one to 1064 individuals per species. The abundances, habitat preferences, and patterns in wing-polymorphism among the species collected were similar to those reported previously from other locations, but important differences were found which reflect the vegetational composition typical of our study area.
3. Wing-morph ratio differences between delphacid populations may reflect strategies for dealing with differences in stability and distribution of their respective habitats. The ratio of macropter/brachypter individuals in various populations of delphacids investigated correlates with the probability that a dispersing individual will find a more suitable habitat patch. The phenomenon is illustrated with a comparison of wing-morph ratios in populations of Prokelisia marginata (Van Duzee) from locations which differ in the extent, distribution, and stability of their stands of Spartina alterniflora Loisl. (smooth cordgrass), the common host of P.marginata .
4. Macroptery is favoured in Atlantic Coast marshes, where habitat patches are differentially suitable, but extensive and predictable. The probability of finding a better patch by dispersing is therefore high.
5. Brachyptery predominates at Cedar Key, Florida, where habitat patches are extensive, stable, and equally suitable during most of the year; and at St Marks, Florida, where resource patches are small, infrequent, isolated, and regularly disturbed. Under these conditions, the probability of finding a better patch by dispersal is low.
6. The conditions at St Marks may have promoted a local host expansion by P.marginata at this location.     

Oral Structure Development and Nuclear Behavior During Conjugation in Paramecium aurelia1

SYNOPSIS. Conjugation in Paramecium aurelia has been studied in live and sectioned cells and oral development studied following ultraviolet microbeam irradiation. The live cells allow a clear correlation to be made between nuclear behavior and gullet development. The paroral cone lies at the level of the buccal overture. The new oral area develops while the old one is still present, the latter structure being still visible after the conjugants have separated. Sectioned material confirms the fact of cytoplasmic fusion at the level of the paroral cones. It also confirms the appearance of new buccal organelles on the right side of the buccal overture of the pre-existing gullet. Ultraviolet microbeam irradiation of the buccal area shows that the posterior edge of the buccal overture must remain undisturbed for normal development. Irradiation of the anterior edge of the buccal overture also affects development. These results differ from earlier work on fissioning cells. Discussion of these differences leads to the conclusion that the factors controlling stomatogenesis are developmentally regulatory.     

Beyond Anthropology: Toward a Man-Science

Culture and Biological Man: Explorations in Behavioral Anthropology. ELIOT D. CHAPPLE.
Ethology: The Biology of Behavior. IREN-ÄUS EIBL-EIBESFELDT. Erich Kling-hammer, trans.
Studies in Animal and Human Behaviour. Volume I. Volume II. KONRAD LORENZ. Robert Martin, trans.