AUXOSPORE FINE STRUCTURE IN A MARINE ARAPHID DIATOM TABULARIA PARVA

Abstract

Recent studies have led to a rapid increase in our knowledge of auxospore structure in diatoms. However, these studies have been limited to centric and raphid pennate diatoms, and there is still very little information on the sexual reproduction in araphid pennate diatoms. Using LM and SEM, the fine structure of the auxospore of the marine epiphytic diatom Tabularia parva (Kützing) Williams & Round were studied. The auxospores were bipolar, as in many other pennate diatoms. SEM revealed a series of transverse perizonial bands that may all be open hoops. No distinct primary transverse perizonial band was detected. A series of longitudinal perizonial bands was observed beneath the transverse series. The well-developed structures of the longitudinal series observed in T. parva have not been reported before in other araphid pennate diatom taxa. Scales were mainly found on the external surface of the perizonium, but curiously they rarely existed on its inner surface, presumably because the scale formation is not strictly regulated during latter stage of centrifugal perizonium development in the pennate diatoms.