AN SEM STUDY OF THE HAPTORAL SCLERITES OF THE GENUS GYRODACTYLUS NORDMANN, 1832 (MONOGENEA) FOLLOWING EXTRACTION BY DIGESTION AND SONICATION TECHNIQUES

Techniques for the preparation of haptoral sclerites of Gyrodactylus s pecies for scanning electron microscopy are described. Enzymatic diges tion using pepsin allows fresh. frozen and alcohol-fixed material to b e examined, but some sclerites, such as the dorsal and ventral bars, a re lost. Sonication of fresh and frozen material retained these access ory bars, including the ventral bar membrane, the guard or sickle fila ment loop on the marginal hooks and even on some occasions ligaments a ssociated with the sclerites. The sclerites of Gyrodactylus spp. from Gasterosteus aculeatus (L.) (three-spined stickleback). Oncorhynchus m ykiss (Walbaum) (rainbow trout) and Salvelinus alpinus (L.) (charr) ar e described from SEM observations following the use of these preparati on techniques, and the articulation between the hamuli and bars is com mented upon.