Morphology and phylogeny of Eudorina minodii (Chodat) Nozaki et Krienitz, comb. nov (Volvocales, Chlorophyta) from Germany

Morphology, sexual reproduction and phylogeny of a colonial green alga coll ected from Germany were studied in culture. Light and electron microscopy o f the gelatinous (extracellular) matrix of vegetative colonies, the absence of obligately somatic cells, and the anisogamous sexual reproduction with sperm packets in this alga indicated that if: is assignable to the genus Eu dorina. This German alga was similar to E. elegans Ehrenberg in its multipl e pyrenoids of nearly identical size and almost identical sized vegetative cells in the colony, but differed from it in having a prominent tubular str ucture (flagellar sheath) surrounding each flagellum in the gelatinous matr ix of the vegetative colonies. Sexual reproduction was homothallic and dioe cious. On the other hand, the vegetative morphology agreed well with that o f Pandorina minodii Chodat with regard to multiple pyrenoids and the promin ent flagellar sheaths. Thus, a new combination, Eudorina minodii (Chodat) N ozaki et Krienitz, is proposed. Molecular phylogenetic analyses of the rbcL -atpB gene sequences from the colonial Volvocales reserved that E. minodii and several heterothallic strains of E, elegans constituted a robust clade. Therefore, prominent flagellar sheaths and homothallic sexual reproduction in E. minodii may be derived characters that evolved recently within the c lade.