Embryonic diapause in the psocid, Peripsocus quadrifasciatus: photoperiod, temperature, ontogeny and geographic variation

ABSTRACT. Embryonic diapause in Peripsocus quadrifasciatus from temperate North America is a maternally-induced, facultative, temperature-dependent response to photoperiod. The length of the critical photoperiod necessary to induce diapause increases approximately 15 min for every degree increase of a population's latitude. Variations in this critical photoperiod cline are probably adaptations to the temperature influences of altitude and other local factors. Nymphs play an important role in reading environmental conditions and determining the adults' response to them. The evidence on cold survival of non-diapausing embryos suggests dormancy as an alternative to winter diapause, particularly in the more moderate, southern latitudes.     

Characterization of an Axenic Strain of Hartmannella vermiformis Obtained from an Investigation of Nosocomial Legionellosis

ABSTRACT. A free-living amoeba identified as Hartmannella vermiformis was isolated from a water sample obtained during an investigation of nosocomial legionellosis. Hartmannella vermiformis is known to support the intracellular multiplication of Legionella pneumophila . This strain of H. vermiformis , designated CDC-19, was cloned and established in axenic culture to develop a model for the study of the pathogenicity of legionellae. Isoenzyme patterns of axenically-cultivated strain CDC-19 were compared with two strains of H. vermiformis derived from the type strain, one axenic (ATCC 50236) and the other grown in the presence of bacteria (ATCC 30966). Enzyme patterns suggested that all three strains are assignable to the species H. vermiformis. Axenic H. vermiformis strain CDC-19 has been deposited with the American Type Culture Collection (ATCC 50237) and should prove useful in the study of protozoan-bacterial interaction.