Dissertation Proposal - The University of Arizona Campus Repository

Also, the number of cells in V. carteri is determined by the number of cleavage divisions
that take place during embryonic development (Section II). Thus, the larger the size a
germ cell reaches before cleavage starts, the higher the number of cells it produces to
develop a daughter colony (i.e. rmax ∝ N 1/3 , Section III).
To find out whether advection and collective flagellar mixing are important for the
productivity of large volvocalean colonies, I measured the increase of the germ cell
diameter in V. carteri during the growth phase for a fixed time period before cleavage
started. I compared the growth rate of V. carteri germ cells that were liberated by
breaking the colonies apart, in deflagellated colonies, and in normal colonies. These germ
cells, outside or inside colonies, were placed in still and artificially mixed medium, with
and without the presence of a flagellar regeneration inhibitor. I hypothesize that germ
cells from colonies that are deflagellated, are inhibited from regenerating flagella
(flagellar mixing prevented), and placed in still medium, have a decrease in their growth
rate. I expect this negative effect to disappear when placing those permanently
deflagellated colonies in a turbulently mixed medium (artificially mixed by air bubbling).
My results were in accord with these expectations. This effect is clearly due to the
modulation of nutrient uptake by advection or its absence.
METHODS
The V. carteri f. nagariensis Eve strain was used for the experiments. To synchronize V.
carteri, the same growth protocol as in Section III was used. When synchronized, V.
carteri completed one asexual life cycle in 48h (Figure 7). Colonies hatch 2h into the
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