title: The diversity of oomycetes on crayfish: morphological vs. molecular identification of cultures obtained while isolating the crayfish plague pathogen.
abstract: Numerous oomycetes colonise the crayfish cuticle, the best known being the crayfish plague pathogen Aphanomyces astaci. Although other oomycetes associated with crayfish complicate the isolation and molecular detection of A. astaci, their diversity is little known. To improve this knowledge, we analysed 95 oomycete isolates obtained during attempts to isolate A. astaci from crayfish presumably infected by this pathogen. We characterized the isolates morphologically and by sequencing of the nuclear internal transcribed spacer (ITS) region. We identified 13 taxa by molecular analysis. Ten of them were assigned to five genera; the remaining three were affiliated with the order Saprolegniales but could not be reliably assigned to any genus. Morphological identification to species level was only possible for 15 % of isolates; all corresponded to Saprolegnia ferax, which was confirmed by ITS sequencing. The most frequently isolated species were S. ferax and Saprolegnia australis. Only seven isolates of A. astaci were obtained, all from one disease outbreak. We show that oomycete cultures obtained as by-products of parasite isolation are valuable for oomycete diversity studies, but morphological identification may uncover only a fraction of their diversity. Further, we show that crayfish may be frequently associated with potentially serious parasites of other organisms.
authors.affiliation: Department of Ecology, Faculty of Science, Charles University in Prague, Viničná 7, Prague 2 CZ-12844, Czech Republic. Electronic address: evikkk@post.cz.
authors.forename: Eva
authors.initials: E
authors.lastname: Kozubíková-Balcarová
authors.forename: Ondřej
authors.initials: O
authors.lastname: Koukol
authors.forename: María P
authors.initials: MP
authors.lastname: Martín
authors.forename: Jiří
authors.initials: J
authors.lastname: Svoboda
authors.forename: Adam
authors.initials: A
authors.lastname: Petrusek
authors.forename: Javier
authors.initials: J
authors.lastname: Diéguez-Uribeondo
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000382:microbiology*; D044822:Biodiversity; D016000:Cluster Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D008853:Microscopy; D008969:Molecular Sequence Data; D009868:Oomycetes / Q000145:classification* / Q000166:cytology / Q000235:genetics / Q000302:isolation & purification*; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer
keywords: Aphanomyces astaci; Internal transcribed spacer; Oogonia; Oomycota; Pathogen vectors; Sequencing