CHAETOTAXY OF MEMBERS OF THE GYRODACTYLIDAE (MONOGENEA), WITH COMMENTS UPON THEIR SYSTEMATIC RELATIONSHIPS WITH THE MONOPISTHOCOTYLEA AND POLYOPISTHOCOTYLEA

This study investigates intra-and inter-generic variation in the chaet otaxy pattern of members of the Gyrodactylidae and compares these data with those from other monogenean groups elucidated by other workers. The staining of surface sensillary structures has revealed areas of ho mology between the two genera Gyrodactylus and Ooegyrodactylus which h ave markedly contrasting modes of reproduction. Although species speci fic maps have been elucidated for members of the genus Gyrodactylus, n o evolutionary trends in their sensillary patterns could be determined . Members of the family Gyrodactylidae are shown to possess a cluster of 3 x 2 sensilla, similar in their size and arrangement to the post-o cular (spa) cluster of sensilla in polyopisthocotyleans, although an t he opposite surface. A comparable cluster of sensilla is lacking in mo nopisthocotyleans. This information gathered from chaetotaxy supports the proposal that the order Gyrodactylidea is close to the polyopistho cotylean line of monogenean evolution.