Cannibals of Oxytricha bifaria (Ciliata, Hypotrichida). Macro- and micro-nuclear DNA content

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Abstract
Investigation of cell differentiation led us to study the giants of Oxytricha bifaria. Here we report systematic variations in nuclear DNA content. Comparing giants, controls starved for 10–14 days, and controls we conclude that (i) the amount of DNA is indicative of the occurrence of cell differentiation, while cell size or nuclear size is not; (ii) the macronuclear DNA content of a giant is about 3.7 times that of the controls; and (iii) the micronuclear DNA content of a giant is about 1.8 times that of the controls. The macronuclear DNA content declines throughout the four successive divisions which typically lead a giant cell back to the normal morpho-physiological state: the amount decreases steadily from a level of about 3.7 times the macronuclear DNA content of the controls to 2.57 and to 1.77 before dropping to 1.08, the normal value.