Ultrastructure of the male gametes from two centric diatoms, Chaetoceros laciniosus and Coscinodiscus wailesii (Bacillariophyceae)

Abstract

The ultrastructure of the male gametes of two centric diatom species, Coscinodiscus wailesii and Chaetoceros laciniosus, is described. The species differ in the presence and configuration of certain organelles and structures, e.g. chloroplasts, Golgi bodies and microtubules (MTs), but both display a deviant configuration of the flagellar apparatus, as in other diatoms that have been examined, viz. a 9 + 0 microtubular configuration in the flagellar axoneme and a ring of nine doublets of MTs in the basal body. MTs were seen to arise from the basal body; in Coscinodiscus wailesii, the MTs formed several small bundles, which radiated in all directions from the basal body and extended down into the cell, whereas in Chaetoceros laciniosus only one bundle of MTs was observed, which was associated with the nucleus. Both species possessed two transitional plates in the flagellar transition region, one at the level of the plasmalemma, the other – less distinct – further into the basal body.