Chloroplast Inclusions in Zoospores of Oedocladium1

SUMMARY Chloroplast inclusions have been studied in zoospores of Oedocladium carolinianum and their ultrastructure compared with the same inclusions previously described in the related genera Oedogonium and Bulbochaete. Structure of the mature pyrenoids is consistent in all 3 genera; the pyrenoid matrix is penetrated by branched cytoplasmic channels delimited by a double membrane system continuous with the chloroplast envelope. Pyrenoids typically arise de novo in zoospores of O. carolinianum. No evidence for the bipartition of a parent pyrenoid has been observed. The incipient pyrenoids of Oedocladium are similar to those found in zoospores of Oedogonium and Bulbochaete, but they frequently demonstrated a crystalline matrix. However, a crystalline matrix was never observed in any mature pyrenoid, even those immediately adjacent to incipient pyrenoids with crystalline structure. Other chloroplast inclusions typical of Oedogonium and Bulbochaete zoospores are the eyespot and striated microtubules. Although the zoospores of O. carolinianum possess striated microtubules, the presence of an eyespot has not been observed.