Analysis of the type of Synedra acus var. ostenfeldii (Bacillariophyta) and its transfer to the genus Fragilaria

Abstract

The type material of Synedra acus var. ostenfeldii Willi Krieg. was investigated using light and scanning electron microscopy. The species is one of the few fragilarioid taxa that forms stellate colonies. Its morphology was compared with that of Fragilaria tenera var. lemanensis Druart, Lavigne & M.Robert, another taxon forming star-shaped colonies, on the type slide and in material from a neighboring lake. The results show both taxa not being conspecific based on valve outline, valve dimensions and presence of spines. Based on the observations, Synedra acus var. ostenfeldii is transferred to the genus Fragilaria as F. ostenfeldii (Willi Krieg.) Van de Vijver, Alexson & Reavie nov. comb. nov. stat. whereas F. tenera var. lemanensis is raised to species level as Fragilaria lemanensis (Druart, Lavigne & M.Robert) Van de Vijver, Ector & Straub stat. nov. Brief notes on their ecology are added.

Revision of the non-marine centric diatom flora (Bacillariophyta) of the sub-Antarctic Campbell Island (southern Pacific Ocean) with the descriptions of five new species

“…13) provide a more detailed indication of the correct locality. The presence of a diatom described from Chile on Campbell Island is, however, not surprising given the presence of more species originally described from southern South America on the island such as Adlafia tenuis Van de Vijver & Goeyers (Van de Vijver et al 2019a) and Planothidium aueri (Krasske) Lange-Bert. (Goeyers & Van de Vijver, unpubl.…”

Analysis of the Fragilaria rumpens complex (Fragilariaceae, Bacillariophyta) with the description of two new species

“…The results of our study contradict this statement, since these taxa are conspecific. Fragilaria fragilarioides can be distinguished from similar taxa such as F. vaucheriae (no colonies, unilateral hyaline central area), F. radians (no colonies, coarser striae), F. pectinalis (no colonies, finer striae), and F. gloiophila (Grunow) Van de Vijver et al (no colonies, narrower valves, unilateral hyaline central area), justifying its recognition as an independent species ( Van de Vijver et al 2020c). Fragilaria pararumpens showed some similarity with F. fragilarioides.…”

Reproductive Compatibility of European Populations of Two Species of Ulnaria (Bacillariophyta)

“…[6], U. verhaegeniana Van de Vijver, M. de Haan, Mertens & Cocquyt [7], с перемещениями видов между родами Ulnaria и Fragilaria Lyngb. [8]. Однако описание новых видов зачастую идет только на основании небольших отличий по морфологическим признакам или даже одному признаку.…”

“…Одним из критериев описания видов рода Ulnaria является форма колоний [8], однако наблюдения за клоновыми культурами U. acus показывают, что в зависимости от стадии жизненного цикла клетки могут вести себя по-разному. В дорепродуктивной фазе жизненного цикла, когда клетки имеют большую длину, они в основном находятся в среде во взвешенном состоянии, лишь часть клеток оседает на дно.…”