The opisthaptor is found on the posterior of all monogeneans. It is purely at attachment organ and is of critical importance in helping these ectoparasites remain attached to their host.
Tetraonchus (top) and Gyrodactylus (bottom) have prominent anchors.
Microcotyle (top) and Nudacirraxine (bottom) have numerous clamps.
Rajonchocotyle has several clamps composed of a sucker (Su) and sclerite (Sc), and also a haptorial appendage (H).
Megalocotyle uas small anchors (A) but numerous large loculi (L).
Pseudacanthocotyle has a tiny true opisthaptor (arrow) but the secondary development of a large spine-covered disk surrounding it.
Sphyranura has two prominent anchors (A), two suckers (S) and many large marginal hooklets (H).
