Culture studies on the life history of Elachista stellaris Aresch. (Phaeophyceae, Chordariales)

Abstract

Culture studies on three isolates of Elachista stellaris from the Mediterranean Sea were carried out in order to re-examine several unusual features reported in the literature. Chromosome numbers in our isolates deviate significantly from previous reports. We find n = 10–12 in contrast to 3–4 given by previous authors. The regular alternation between haploid microthalli and diploid macrothalli is confirmed. Both phases can reproduce asexually by plurizoids. Meiosis occurs in unilocular sporangia of the macrothalli. The diploid phase is re-established in the trichothallic meristem of young macrothallus filaments developing on the creeping microthallus. Quantitative microspectrofluorometry permitted us to localize this ploidy-increase within consecutive cells of single filaments. In accordance with previous reports, no evidence for syngamy was found. Elachista stellaris seems therefore to be an apomictic species and its nuclear phases are connected by meiosis and somatic diploidization.