1 Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Branišovská 1160/31, 370 05 České Budějovice, Czech Republic. Electronic address: lisnerova@paru.cas.cz.
2 Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Branišovská 1160/31, 370 05 České Budějovice, Czech Republic.