Chromosomes of the brown algae

Abstract

Investigations concerning brown algal chromosomes have contributed to our understanding of the reproductive biology of brown algae. Techniques used in observing chromosomes in the light microscope are briefly summarized. Mitosis and meiosis are discussed, with an emphasis on aspects that are distinctive in the brown algae. Observations of chromosome morphology, although limited by the small size of brown algal chromosomes, have provided evidence for the existence of sex chromosomes. The few investigations quantifying brown algal genomes, and the potential for such techniques in further studies, are discussed. Most studies of brown algal chromosomes have been concerned with chromosome numbers, and reports for 183 species are presented along with discussions of the implications of these numbers on discerning basic chromosome numbers and patterns of chromosome numbers in taxonomic groups, and polyploidy. Many studies of brown algal chromosomes have been made in conjunction with life history studies, in order to establish the position of meiosis and karyogamy. Chromosome studies have been useful discovering departures from the typical life history, such as apomeiosis, apomixis, and spontaneous increase in chromosome number. Hybridization is discussed as a special case in which two different sets of chromosomes are combined.