The need for an extracellular component for cell pairing in Tetrahymena.
Abstract Cell pairing in Tetrahymena takes place among cells that have undergone a prepairing interaction, co-stimulation. Pairing does not take place if co-stimulated cells are washed free of their conditioned medium, but washed co-stimulated cells will pair if restored to either co-stimulation conditioned medium or starvation conditioned medium. This demonstrates a need for an extracellular factor in the pairing reaction.
summary ::: Populations of diploid and autotetraploid Anthoxanthum alpinum A. & D. Love formed a narrow hybrid zone in a study area in the Swiss Prealps. Detailed vegetation analyses were performed along transects in several contact zones between the two cytotypes. The vegetation differed according to the position in the hybrid zone. When considering the hybrid zone as a whole, and for one transect that was analysed in detail, there was strong evidence for habitat segregation between the cytotypes. Vegetation transitions, habitat preference and segregation of the two cytotypes differed according to location in the hybrid zone. The origin and dynamics of the hybrid zone are discussed.