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ŠUMARSKI LIST 7-8/2019 str. 33     <-- 33 -->        PDF

Spore viability of microsporidian species isolated from gipsy moth larvae (Lymantria dispar) after long-term storage in liquid nitrogen
Vitalnost spora mikrosporidija izoliranih iz gusjenica gubara (Lymantria dispar) nakon dugotrajne pohrane u tekućem dušiku
Daniela Pilarska, Manana Kereselidze, Gernot Hoch, Andreas Linde
Data on the viability of microsporidian isolates from Lymantria dispar after long-term storage in liquid nitrogen are presented. Eight microsporidian isolates from L. dispar were tested for their infectivity against L. dispar larvae: ­Vairimorpha disparis, Nosema lymantriae, Nosema portugal, Nosema sp. (Poland), Nosema sp. (Ebergassing), Nosema sp. (Germany), Nosema sp. (Schweinfurt) and Nosema sp. (Veslec). The survival of spores in liquid nitrogen was ­studied in detail for N. portugal and Nosema sp. (Ebergassing) which had been stored in liquid nitrogen almost 19 years and used for individual per oral infections while the other six isolates were used only in surface contamination per oral experiments. Our study confirms that storage in liquid nitrogen is a suitable option for long-term storage of Nosema and Vairimorpha species from lepidopteran hosts. Spores survived for up to 19 years; however, the experiments show that there is a significant loss of viability. In some cases, spores had lost viability already after 7 years in liquid nitrogen. We recommend producing fresh material every 5 years to maintain collections in liquid nitrogen. No material that had been stored in liquid nitrogen for extended periods should be used for infection experiments.
Key words: microsporidia, spore viability, long-term storage, liquid nitrogen
Microsporidia are single-cell pathogens related to the Fungi, infecting animal hosts from all major taxa. Insects are the most commonly reported hosts and at least 80 microsporidian genera are known from insect hosts. As primary pathogens, microsporidia often play an important role in the regulation of insect populations (Solter et al., 2012). Effects of infection are generally rather chronic, leading to only low or moderate mortality (Hoch and Solter, 2018). Microsporidian infection frequently decreases host reproduction and feeding, and epizootics in the host population can reduce populations and, thus, damage to host