Zygnema has short, unbranched filaments composed
of cylindrical cells within a mucilage sheath. Each cell has
two stellate chloroplasts, each with a large central pyrenoid.
The nucleus is located within the cytoplasmic bridge connecting
the two chloroplasts (arrow, below image). The basal cells occasionally
develop rhizoidal growths for attachment in turbulent waters.
The
large, distinctive star-shaped chloroplasts easily distinguish
Zygnema from other filaments.
