New records and the first SEM description of a rare diatom Cavinula lapidosa (Krasske) Lange-Bertalot (Bacillariophyta)

Abstract

Cavinula lapidosa (Krasske) Lange-Bertalot is a rare species found in oligo- and mesotrophic waters with low electrolyte content, on swamps, wet rocks, mosses and bogs. The occurrence of C. lapidosa was recorded during an analysis of the diatom diversity in Poland. This species was found in the headwaters of Jamów stream and a tributary of River Wisłoka from 2007 to 2014. Cavinula lapidosa is a diatom considered "extinct" or "probably extinct" within the territory of Poland. The species develops mainly in the upper, shaded sections of streams, always as single cells among mosses growing on rocks and rarely on the rocks themselves. In 2018–2019 numerous population of this species was found on mosses overgrowing an old abandoned basement in the Wisłoka River basin area. In this study, the lectotype slide of Navicula lapidosa was examined using light microscopy, and based on the collected samples, the first SEM observations of the ultrastructure of the valves were made.