Karyology and nuclear DNA quantification in Bryopsis (Chlorophyta) from North Carolina, USA

Abstract

Chromosome numbers for three species of Bryopsis (Codiales, Chlorophyta) from the warm temperate coast of North Carolina are presented. Bryopsis hypnoides Lamouroux, and B. plumosa (Hudson) C. Agardh have chromosome complements of 1 N = 10, while in B. pennata Lamouroux 1 N = 8. The results obtained by microspectrophotometry with the DNA-localizing fluorochrome hydroethidine, and karyotype comparisons, failed to distinguish B. hypnoides and B. plumosa. By contrast, regional isolates of B. pennata all had a significantly smaller genome than the above species. In B. hypnoides, identical If values for nuclei in gametes and vegetative macrothalli confirmed the mitotic nature of gametogenesis. A small (< 10%) but constant number of these gametes were binucleate, with nuclei having a If amount of DNA. In addition, nuclei in older main axes were apparently endopolyploid, with If values indicative of 4C DNA levels. Incorporation of microspectrophotometric data for two angiosperms with known 2C DNA contents permitted quantification of If values for Bryopsisplants. Extrapolated 2C DNA contents for B. hypnoides and B. plumosa, respectively, are 1.0 pg and 0.7 pg for B. pennata. It is concluded that Bryopsis is represented by two species in North Carolina: B. pennata, and a second entity whose morphotypes have been referred variously to B. hypnoides and B. plumosa.