Karyological investigations on the genus oedogonium link (Oedogoniales, chlorophyceae)

Abstract

Six dioecious macrandrous and three monoecious macrandrous taxa of Oedogonium Link were studied cytologically and subjected to karyotypic analyses. Nuclear events conformed to the standard pattern of mitosis met with in typical eukaryotes. The chromosome numbers exhibited by various taxa are Oe. gracilius var. globosum, n = 13; Oe. hindustanense, n = 17; Oe. lemmermannii, n = 19; Oe. hatei, n = 21; Oe. plagiostonum f. minuta, n = 22; Oe. calcareum, n = 32; Oe. intermedium f. tenuis, n = 21; Oe. pseudaureum var. maius, n = 25 and Oe. tropicum, n = 37. These taxa were investigated for the first time and most of the chromosome numbers represented new counts for the genus. A perusal of chromosome number revealed that aneuploidy has played a more efficient role in the speciation and evolution of this genus. Furthermore, clear differences in karyotypes of the taxa with common chromosome numbers indicated positive role of chromosomal rearrangements in speciation of the genus Oedogomum. Lack of identifiable sex chromosomes in macrandrous homothallic taxa and the presence of identical karyotypes- chromosome number and morphology in the male and female strain of macrandrous heterothallic taxa clearly suggested that sex differentiation, in Oedogonium, is controlled by genes rather than specific sex-chromosomes. Thus, the decisive role of genes in the evolution of taxa investigated cannot be ignored. © 1990 Taylor & Francis Group, LLC.