Abstract
Studies on the diversity, distribution and ecological role of Saprolegniales (Oomycota) in freshwater ecosystems are currently receiving attention due to a greater understanding of their role in carbon cycling in various aquatic ecosystems. In this study, we characterized several Saprolegniales species isolated from Anzali lagoon, Gilan province, Iran, using morphological and molecular methods. Four species of Saprolegnia were identified, including S. anisospora and S. diclina as first reports for Iran, as well as Achlya strains, which were closely related to A. bisexualis, A. debaryana and A. intricata. Evaluation of the ligno-, cellulo- and chitinolytic activities was performed using plate assay methods. Most of the Saprolegniales isolates were obtained in autumn, and nearly 50% of the strains showed chitinolytic and cellulolytic activities. However, only a few Saprolegniales strains showed lignolytic activities. This study has important implications for better understanding the ecological niche of oomycetes, and to differentiate them from morphologically similar, but functionally different aquatic fungi in freshwater ecosystems.
Highlights
Saprolegniales, as a monophyletic order, belong to the phylum Oomycota
From all oomycetes isolated from the three locations sampled along the year, 511 out of 720 (* 71%) were assigned to the order Saprolegniales
We were able to confirm the occurrence of four Saprolegnia spp., of which Saprolegnia anisospora and S. diclina have never been reported from Iran
Summary
Saprolegniales, as a monophyletic order, belong to the phylum Oomycota. It includes biflagellate heterotrophic microorganisms that have eucarpic mycelial and coenocytic thalli of unlimited growth. They produce asexual (sporangia) and sexual (gametangia) structures delimited by septa. Saprolegniales are mainly predominantly freshwater saprophytes of plant and animal debris (Beakes and Sekimoto 2009). This order contains three families: Achlyaceae (four genera), Saprolegniaceae (11 genera) and Verrucalvaceae (7 genera) (Beakes et al 2014; Molloy et al.2014; Beakes and Thines 2017; Rocha et al 2018). Achlya, Brevilegnia, Dictyuchus, Leptolegnia, Plectospira, Saprolegnia and Thraustotheca have been commonly reported to inhabit freshwater ecosystems (Czeczuga et al 2005; Mousavi et al 2009; Marano et al 2011)
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