Einkerniges Protonema beiBryopsis undPseudobryopsis myura

Abstract

A protonema with a giant nucleus has already been reported forBryopsis hypnoides (Neumann 1969a). The same has now also been found in cultures ofBryopsis monoica. The single nucleus of the protonema reaches about eight times the diameter of the vegetative nuclei in the multinucleate thallus. This giant nucleus contains a long sinuous nucleus similar to that ofAcetabularia mediterranea. Prior to the adventitious formation of the pinnate thalli, transition to the multinucleate stage takes place. The division of the giant nucleus had been observed before inBryopsis hypnoides. The protonema ofBryopsis monoica is capable of holocarp formation of gametes immediately after transition to the multinucleate stage. A mononucleate protonema has further been found inPseudobryopsis (=Trichosolen)myura which fully developed in culture. The protonema is lobed, wound, and irregularly branched. The nucleus increases too, but does not reach the proportions of that ofBryopsis species, and the nucleolus does not become elongate. The transition to the multinucleate stage is accomplished when the development of the pinnate thalli begins. Prior to the formation of the pinnules the young thalli ofBryopsis hypnoides andPseudobryopsis myura resemble each other, especially at their base on the protonema. These similarities, revealed in cultivated specimens, point to a closer taxonomic relation between the generaBryopsis andPseudobryopsis than has hitherto been assumed.

Zusammenfassung

1. Wie bei der siphonalen GrünalgeBryopsis hypnoides, so konnte auch fürBryopsis monoica ein Protonema mit einem Riesenkern nachgewiesen werden. Der Nucleolus dieses Kerns ist ebenso langgestreckt und gewunden, aber auch im Endstadium noch deutlich vakuolisiert.

2. Das Protonema vonBryopsis monoica besitzt die Anlage zur Holocarpie, d. h. es vermag unmittelbar nach dem Übergang in das vielkernige Stadium seinen ganzen Inhalt in Schwärmer umzuwandeln.

3.Pseudobryopsis myura besitzt ebenfalls ein einkerniges Protonema-Stadium, aus dem in gleicher Weise wie beiBryopsis hypnoides die vielkernigen Fiederthalli adventiv hervorsprossen. Der Kern des Protonemas schwillt auch an, erreicht aber nicht die Größe wie beiBryopsis, und derNucleolus bleibt mehr oder weniger abgerundet.