Microscopy

Gylletråd forms mats up to 2 mm thick, light green in color, composed of unbranched filaments approximately 10 μm thick. The cells are 6–7 μm in diameter and 3–9 μm in length, with 0.3–0.5 μm thick, warty cell walls. Typically, there is a single flattened chloroplast with irregularly lobed edges, pressed against the cell wall and lacking a pyrenoid. Cells have a large, central nucleus. Zoospores have not been observed, but the filaments grow through intercalary cell division. Asexual reproduction occurs via filament fragmentation and the formation of non-motile autospores.

 

Unlike the powdery Apatococcus species, gylletråd exhibits transverse division planes, which result in chains of paired cells adhering to one another, contributing to filament elongation.