TAXONOMY, MORPHOLOGY AND ECOLOGY OF BIRENZIS-LUCENS COMB-NOV (BACILLARIOPHYTA) - A BRACKISH-MARINE, EENTHIC DIATOM SPECIES COMPRISING DIFFERENT MORPHOLOGICAL TYPES

Biremis lucens (Hustedt) Sabbe, Witkowski et Vyverman is a common and widespread benthic diatom species in brackish and marine sediments. It usually forms small colonies which are firmly attached to sandgrains. A LM and SEM description of specimens from different localities in Eu rope, Africa and Australasia (including the type locality) is given. I n addition, its taxonomy and ecology are discussed in detail. Morphome tric analysis of a large number of valves revealed the presence of two distinct morphological types in the European material. It is argued t hat these types do not merely represent different forms in a cell size reduction cycle but constitute distinct entities with different morph ologies and different ecological requirements. The morphological varia tion patterns in the African and Australasian material did not corresp ond to the European ones. The significance and taxonomic implications of these observations are discussed.