Phylogenetic tree resulting from the neighbor-joining analysis of the 18S rRNA sequences obtained from Pseudorasbora parva sampled in France and Sphaerothecum destruens sequences from GenBank, using MEGA4 software. The Dermocystidium salmonis 18S rRNA sequence was used as an outgroup. The bar represents 1% sequence divergence. The evolutionary distances were computed using the Maximum Composite Likelihood method and expressed as the number of base substitutions per site. Accession numbers are indicated in parentheses. Fish species associated with S. destruens infection, country of discovery and reference are from ¹topmouth gudgeon in the Netherlands (Spikmans et al., 2013); ²topmouth gudgeon in France (this study); ³Chinook salmon in Washington, US (Arkush et al., 2003); ⁴Atlantic salmon in US (Arkush et al., 2003); ⁵sunbleak in United Kingdom (Paley et al., 2012); ⁶winter-run Chinook salmon in California, US (Arkush et al., 2003).