KARYOLOGY AND CYTOPHOTOMETRIC ESTIMATION OF NUCLEAR-DNA VARIATION IN SEVERAL SPECIES OF POLYSIPHONIA (RHODOPHYTA, CERAMIALES)

Results are given for a karyological investigation of 13 species of Po lysiphonia from the North Atlantic Ocean and adjacent seas. Chromosome complements of 1 N = 28-36 are newly reported for six species. Micros pectrophotometry with the DNA-localizing fluorochrome DAPI is used to estimate nuclear genome sizes. Incorporation of fluorescence values fo r chicken erythrocytes (RBC) permitted quantification of If values for nine Polysiphonia species. The 2 C DNA contents range from 0.8-2.2 pg . The absence of a positive correlation between estimated genome size and 1 N chromosome complement excludes the possibility that speciation has resulted exclusively from loss or gain of chromosomes and associa ted genome. Information for chromosome numbers, karyotype symmetry and nuclear genome size for species of Polysiphonia is compared with kary ological data for two other genera of red algae, Gracilaria and Porphy ra, which are represented by large numbers of species.