Body Size, Genome Size, and Intrinsic Rate of Increase in Ciliated Protozoa

The relationship between rm and body size for ciliates was reviewed using data mostly culled from the literature. Even over a 3.5 order of magnitude range in body volume, size alone only accounts for about 42% of the variation in rm. Data were presented which indicate that the residual variation is related to the relative size of the macronucleus and micronucleus, which is interpreted to reflect genome size. Ciliates which can multiply quickly for their size have relatively small micronuclei or genomes for their size and vice versa. It is suggested that nuclear dualism, like multicellularity, is a means of attaining a degree of independence between body size and rm. These ideas are discussed with respect to the r-K selection hypothesis and the ecological properties of species. We suggest that rm or size should not be used alone as indicators of a species position on the r-K continuum. The potential of these results as a basis for estimating growth rates of wild populations is noted.