The oogonial aperture of Oedogonium decipiens var. decipiens (Oedogoniales, Chlorophyta) and its systematic significance

Abstract

According to traditional taxonomical criteria, the fertilization aperture in the genus Oedogonium has been classified into pore or circumcision type. To contribute with information useful to clarify the systematics of the Oedogoniales, we have studied the oogonial aperture in O. decipiens var. decipiens showing a circumcision in median position. The aperture mechanism and associated structures (line of weakness and thin layer) are similar to those previously described in O. cardiacum. The type and position of the aperture in mature oogonia was also studied in other seven Oedogonium species. In all the analyzed species, the fertilization aperture occurs along the line of weakness, but they would differ only in the opening degree of this line. Therefore, the types of oogonial aperture would not be so different as to discriminate groups of species belonging to the genus Oedogonium, in agreement with a previous molecular phylogenetic study of this group of algae.