Extreme morphological variation between related individuals of Gyrodactylus pungitii Malmberg, 1964 (Monogenea)

An example of extreme morphological variation in a gyrodactylid monogenean is described. A specimen of Gyrodactylus pungitii collected from Pungitius pungitius at Crowland, Lincolnshire, UK, was found to have very short, slightly asymmetrical hamuli with roots only 12 and 15 µm long, compared to 16–28 µm in typical specimens of this species. When the specimen was cloned on G. aculeatus, the grand-daughter was found to be a typical specimen of G. pungitii. This extreme morphological variation, which was not inherited by the offspring, highlights the dangers of describing gyrodactylids from single small collections of parasites.