Ultrastructure of the flagellar apparatus of the gametes ofGongrosira papuasica(Chlorophyta)

Abstract

Gongrosira papuasica is the only known filamentous, branching chlorophycean alga to produce biflagellate gametes. The flagellar apparatus of the gametes exhibits 180° rotational symmetry and clockwise absolute orientation. In addition, the gametes have a distal fibre and proximal sheaths similar to those of Chlorosarcinopsis. Other features include a double-banded, striated distal fibre, a 4-2-4-2 pattern of the microtubular rootlets with associated electron-dense material, two rhizoplasts, a mating structure, and a pyrenoid penetrated by thylakoid membranes. The 2s rootlet extends near to the eyespot in the chloroplast. The characteristics of trentepohlialean vegetative filaments and motile cells, including the pits and transverse walls of vegetative cells, and the multi-layered structures, overlap of basal bodies, and keeled flagella of motile cells were not observed. Although the vegetative morphologies of Gongrosira and Chlorosarcinopsis are dissimilar, the ultrastructure of G. papuasica gametes and t...