Zur Entwicklungsgeschichte der EpithemiaceenEpithemia, Rhopalodia undDenticula (Diatomophyceae) und ihre vermutlich symbiotischen Sphäroidkörper

Abstract

InEpithemiaceae gametogenesis and gamete fusion are uniform and unique. Former contrary descriptions of the behaviour ofRhopalodia gibba are erroneous. OnlyDenticula tenuis which is aberrant also in other respects offers some modifications. The mature gametes in the partners reach only an oblique position instead of turning round by 90° as in other pennate Diatoms. In this oblique position the fusion is accomplished. With regard to the dorsiventrality of the mother cell a turn on the right or the left is realized. In the partners of one pair the direction of turning corresponds or is opposite. In one species one direction and one combination in a pair is strongly favoured, in other species they seem to happen by chance. A sib ofEpithemia turgida produces obligatorily automictic auxospores by paedogamy under maintenance of the special mode of gametogenesis in allogamous species. As a new diagnostic character ofEpithemia species the cross section image of cells has been found. The perizonium exhibits a lattice structure. The epitheca of the primary cell has a complete girdle with intercalary band. The so-called sphaeroid bodies for some reasons can be interpreted as symbionts.