The haptor is the attachment organ of the

monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...

ns, a group of parasitic Platyhelminthes. The haptor is sometimes called opisthaptor (from ''opistho-'': behind) to emphasize that it is located in the posterior part of the body, and to differentiate it from the prohaptor (from ''pro-'': in front), a structure including glands located at the anterior part of the body. According to Yamaguti (1963), the chief adhesive organ of the monogeneans, the haptor, is posterior, more or less discoid, muscular, may be divided into alveoli or loculi, is usually provided with anchors, has nearly always marginal larval hooklets, or is in a reduced form with anchors. The haptor may consist of symmetrical or asymmetrical, sessile or pedunculate, muscular suckers or clamps with or without supporting

sclerite A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...

s; accessory adhesive organs may be present in form of armed plaques, lappets or appendices. The structure of the haptor is different in the two major groups constituting the

Monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...

, namely the Polyopisthocotylea and the

Monopisthocotylea The Monopisthocotylea are an inferior class of parasitic flatworms in the class Monogenea.WoRMS (2019). Monopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119219 on 2019-02-08 Yamaguti, S. (1963). Systema Helmi ...

, and is an important part of the diagnosis in both groups. * In the Polyopisthocotylea, the haptor usually bears several clamps or suckers, and is often asymmetrical. * In the Monopisthocotylea, the haptor comprises a single, symmetrical attachment unit, and has never haptoral clamps.Whittington, I. D. (2005). Monogenea Monopisthocotylea (ectoparasitic flukes). In K. Rohde (Ed.), Marine Parasitology (pp. 63-72): CSIRO, Collingwood, Australia & CABI, Oxon, UK. In the family

Diplectanidae The Diplectanidae are a family of monopisthocotylean monogeneans. They are all parasitic on the gills of fish (marine or freshwater). Diplectanids are small animals, generally around 1 mm in length. As parasites, they can be extremely numero ...

, the haptor bears special structures (one ventral and one dorsal) called squamodiscs or lamellodiscs.

References

{{reflist Platyhelminth anatomy Animal morphology Monogenea Monopisthocotylea Polyopisthocotylea