The egg bundles of the monogenean Dionchus remorae and their attachment to the gills of the remora, Echeneis naucrates

Gills of three remoras, Echeneis naucrates L., from Heron Island, Queensland, Australia had few adults but many attached egg bundles of the monogenean, Dionchus remorae. Studies of fresh, and preserved and cleared, primary gill lamellae bearing egg bundles and investigations with scanning electron microscopy and serial wax sections reveal proliferated host epithelium surrounding and embedding part of a loop of egg-shell material to which eggs are tethered, but eggs in each bundle hang free of gill tissue. This hyperplasia appears to anchor egg bundles to the host's gills. However, hyperplasia will take time to develop and cannot play a part in tethering newly laid egg bundles. Possible advantages to the parasite by attaching eggs to the gills of its host include improved oxygenation of the eggs, and a reduced risk of egg predation. Egg attachment by D. remorae to their remora hosts seems well adapted to successful larval invasion of fish which exhibit phoresy.