Freeze fixation-dehydration as a method of preparation of Gyrodactylus (Monogenea) for SEM

Freeze fixation-dehydration was used for the first time in the preparation of attached Gyrodactylus for SEM viewing. The technique provided instant immobilization of specimens before death and negligible shrinkage throughout the fixation-dehydration process. Comparisons of sample means of two linear measurements of attached opisthaptors showed 20% more shrinkage of Gyrodactylus fixed using 10% neutral buffered formalin than those which were freeze fixed. Freeze fixation-dehydration was excellent for the study of gross external morphology of attached Gyrodactylus. However, the freeze fixation-dehydration process may cause disruption of intracellular structural components making delicate tissues brittle and more prone to damage during subsequent manipulation.