Evolution of The Number of Sexes
Most diploid organisms have two sexes, but some have three or more. For instance, among ciliates in which mating occurs by the contact of two diploid cells and the subsequent exchange of haploid genome, cells are grouped into several mating types (or sexes) so that mating occurs only between cells of different sexes (sonneborn, 1939). Stylonychia spp. have as many as 48 sexes (Ammermann, 1965). Other organisms with three or more sexes are fungi, in which mating occurs by the fusion of isogamous haploid gametes (Raper, 1966).
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- Ammermann, D. 1965 Cytologische und genetische Untersuchungen an den Ciliaten Stylonychia mytilus Ehrenberg. Arch. Protistenk 108: 109–152.Google Scholar
- Dini, F. and P. Luporini, 1985 Mating-type polymorphic variation in Euplotes minuta (Ciliophora: Hypotrichida) J. Protozool. 32: 111–117.Google Scholar
- Grell, K.G. 1967 Sexual reproduction in protozoa. pp147–213. In T.T. Chen (ed.) Research in protozoology. Vol. 2 Oxford: Pergamon Press.Google Scholar
- Iwasa, Y. and A. Sasaki, 1987 Evolution of the number of sexes. Evolution (in press)Google Scholar
- Nobili, R. 1966 Mating types and mating type inheritance in Euplotes minuta Yocom (Ciliata, Hypotrichida). J. Protozool. 13: 38–41.Google Scholar
- Raper, J.R. 1966 Life cycles, basic patterns of sexuality, and sexual machanisms. pp 473–511. G.C. Ainsworth and A.S. Sussman (eds.), The fungi: an advanced treatise. vol. 2, the fungal organism. New York: Academic Press.Google Scholar