Many amphibians are known to suffer embryonic die-offs as a consequence of an emergent disease known as ‘Saprolegnia infections’. Thus far, the only species of Saprolegnia shown to be involved in natural infections is Saprolegnia ferax. In this study, we have isolated and characterized another Saprolegnia species responsible for ‘Saprolegnia infections’ on embryos of Bufo calamita in mountainous areas of central Spain. The strain was identified as belonging to Saprolegnia diclina based on morphological, physiological and molecular characters (sequencing of the internal transcribed region of ribosomal DNA). Zoospores of the new strain were able to infect embryos of Bufo calamita, and the symptoms observed were the same as those observed in natural infections. The results emphasize the need to carry out isolations and characterizations of the species and/or strains involved in this emergent disease. This will be important in order to design strategies to prevent the impact and spread of species (or strains) pathogenic to amphibians.
Future studies need to be done regarding identification and characterization of species of Saprolegnia causing amphibian embryo die-offs and to differentiate opportunistic Saprolegnia growing in dead eggs from species or strains of Saprolegnia able to grow as primary invaders in amphibian eggs. This is a crucial aspect for designing strategies in order to prevent the impact and spread of species (or strains) pathogenic to amphibians. These strategies might include, for example, the management of species that can act as vectors for pathogenic Saprolegnia species, such as in fish and crustacean restocking practices
Saprolegnia diclina: another species responsible for the emergent disease ‘Saprolegnia infections’ in amphibians. FEMS Microbiology Letters 279 (1), 23–29