The Buccal Organ of Some Monogenea Polyopisthocotylea

Light and electron microscopic studies of the 'buccal suckers' of Gotocotyla secunda showed that they are complex structures with muscular, glandular, (resorptive?), and probably sensory components. The name 'buccal organ' is therefore proposed for them. Ducts run from the lumen of the buccal organs to their dorsal, ventral and lateral surface and communicate with lacunae surrounding them. The surface of the ducts and of the muscular walls of the buccal organs are lined by tegument with short microvilli, tegument with dense, long surface lamellae, and tegument with thick, long microvilli which have an electron-dense core. The latter type of tegument contains many vesicles and electrondense ovoid bodies, and is traversed by gland ducts containing large secretory droplets. Electron microscopic examination showed that the prebuccal convoluted structures in Heteromicrocotyloides mirabilis are a modified tegument connected to subtegumental cells. Light microscopic studies of Gotocotyla bivaginalis. Pseudothoracocotyla indica, Pricea multae and Heteromicrocotyla australiensis showed that the first three species have buccal organs similar to those in G. secunda , whereas the last species resembles H. mirabilis. It is tentatively assumed that the buccal organs play a role in finding suitable sites for bloodfeeding.