Scytothamnus australis has a unilocular sporangia reproductive structure which means that it can produce meiospores or asexual spores.

The gametophytes are dioecious (Dioecy) but no structural difference can be detected between the gametangia of male and female isolates.

In the course of the first few divisions the chloroplast loses its characteristic star-shaped shape and the pyrenoid becomes smaller and occupies a side position.

Subsequently the nuclei are concentrated near the outer areas of the cytoplasm, and flagella appear to divide into separate types within vesicles before the division of individual meiospores (spores produced by meiosis).

In the cytoplasm, smooth endoplasmic reticulum (ER) became noticeable and the number of membrane-bound electron-dense (possibly lipid) bodies increased.

Following this, flagella appear within cytoplasmic vesicles and the paired centrioles of the vegetative cells take on the function of basal bodies (organelles that form the base of a flagellum or cilium).

Fertilization was a not very noticeable process by which motile (able to move) gamete (male) approached an unmoving one (female) and, following contact, the two cells fused rapidly.

The development of zygotes and unfused gametes follow the same pattern leading directly to the formation of parenchymatous sporophytes.

Cells of the filament, frequently those lying next to a hair are transformed into peaks and developed into erect, parenchymatous sporophytes.

After gametophytes had been maintained in culture for prolonged periods, exceeding 2 years, they failed to respond to the short-day stimulus, appearing to have lost the capacity to produce gametangia.

Tanaka, Atsuko; Nagasato, Chikako; Uwai, Shinya; Motomura, Taizo; Kawai, Hiroshi (September 2007).

"Re-examination of ultrastructures of the stellate chloroplast organization in brown algae: Structure and development of pyrenoids".