Ultrastructure of the type material of Encyonema leibleinii and E. lacustre (Cymbellales, Bacillariophyta)

Abstract

Encyonema leibleinii and E. lacustre were among the first species of Encyonema to be described, in 1830 and 1824, respectively. Until now, however, only light microscopic features (and SEM of non-type material for E. lacustre) of these species have been documented. Here, we provide ultrastructural (scanning electron micrograph) characterization of their type material. We find that the SEM , as well as LM, features of E. leibleiniiare indistinguishable from those of E. prostratum and E. paradoxum. Consequently, the results support the synonomization of the three taxa, with E. leibleinii having priority as the first name applied to this entity. Encyonema leibleinii and E. lacustre have similar ultrastructural characteristics, mainly concerning the internal stria structure, and the terminal and central raphe fissures. Based on this information and SEM characterizations in the literature, ultrastructural features of the genus Encyonema are discussed.