Life history of Cladophora surera sp. nov. (Cladophorales, Ulvophyceae).

The life history of Cladophora surera sp. nov., described from the south of the province of Buenos Aires, Argentina, was found to be diplobiontic and isomorphic with haploid gametophytic (n = 24) and sporophytic (2n = 48) plants. Other freshwater species, namely C. suhri-ana K ü tz. and C. callicoma Kü tz. have also been reported to be diplobiontic and isomorphic but differing from C. surera by their ploidy Level. Plants exhibit great morphological variation, as the number of branches/mm[sup2] tends to increase with higher water velocity, thus adopting morphotypes that resemble very different species, that is, C. vagabunda (L.) Hoek, C. glomerata (L.) K ü tz., C. laetevirens (Dillw.) Kütz., C. brasiliana Martens, C. dalmatica Kü tz., C. vadorum (Aresch.) Kü tz. and C. rivularis (L.) Hoek., but clearly differing from them by other morphological parameters; apical cell diameters. The ploidy level 24/48 has riot been established for a species of Cladophora. Autogamy is the normal conjugation method and can take place even inside the gametangia before the gametes are released. Iso-gametes conjugate in a slow behavioral anisogamy, in which the contents of one migrate to the other. Tetra-flagellate zoospores result from meiosis. [ABSTRACT FROM AUTHOR]