Electron Microscopic Observations on the Differentiation and Release of Spermatia in the Marine Red Alga Polysiphonia Hendryi (Ceramiales, Rhodomelaceae)

Spermatial differentiation in Polysiphonia hendryi begins after nonpolar, avacuolate spermatia are cleaved from their mother cells. The spermatia and their mother cells are embedded within the spermatangium, a confluent wall matrix of the male branch. As the young spermatium enlarges and becomes ellipsoid, the wall fibrils of the spermatangium are compressed, forming a separating layer. Spermatia become polar with rough endoplasmic reticulum coalescing to form a large, fibrillar spermatial vacuole that becomes extracytoplasmic in later development. Following spermatial vacuole formation, dictyosomes form and deposit a spermatial wall, severing the spermatial mother‐cell pit connection. Enlargement of younger spermatia, which are lateral to the older ones, squeezes the maturing spermatia, pushing them from the male branch, and leaving a scar that compresses and heals. Through this release mechanism, new sites are created for additional spermatial proliferation.