Ciliates in the “Maare” (mires) of Bornheim: local diversity of Spirostomum spp.

Thilo Bauer (Bornheim, Germany)

Eight morphospecies of Spirostomum spp. are valid species until present day. Despite morphological differences exist, the Spirostomum minus clade is considered as environmental modification because of genetic similarities. This work presents the current state of a privately funded project to monitor ciliate species living in the mires of Bornheim, North Rhine-Westphalia, Germany. About 20 ephemeral mires are spread over an area of approximately 35 square kilometres. A novel fluorescence double staining method is successfully tested to observe ciliate species using a fluorescence microscope. Fluorescent life-cell imaging supports quick determination of species, isolation of individuals for further cultivation, and replaces well the classical methyl green-pyronin staining. Samples taken from several mires yielded new insights about the local diversity of Spirostomum spp. Along with Spirostomum ambiguum and Spirostomum teres multiple morphologically different types of Spirostomum minus are found abundant in the samples. A new green Spirostomum strain with no symbiotic algae is reported here for the first time. White hyaline strains of similar size and shape are also abundant. Present observations confirm existence of at least two hyaline and slender morphospecies, similar to Sp. minus depicted by Kahl (1932). They mainly differ in the length of the AZM, with 1/3 and 1/2 of the total length of individuals, respectively. A small morphospecies of about 200 μm in length with a moniliform macronucleus of 6-10 nodules and multiple micronuclei is found similar to a short Spirostomum sp. Multiple Spirostomum minus strains often are found in dense clumps within the samples. The different morphotypes do not change their shape when isolated in culture. Current observations support well the idea of Kahl (1932) to split the Spirostomum minus clade into distinct species, of which he described Spirostomum intermedium and Spirostomum minus. Three suggested new morphospecies are described here.

40th Jahrestagung der Deutschen Gesellschaft für Protozoologie, 22.-25. Februar 2021