Subclass MONOPISTHOCOTYLIDEA

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Introduction

Monopisthocotyleans infect a diversity of microhabitats across many fish groups, can move readily, feed on epithelial cells and have a haptor forming a single, symmetrical attachment unit. Most adult monopisthocotyleans have proteinaceous sclerites in the form of 14 or 16 small hooklets usually around the haptor periphery for attachment to host epithelial cells. Larvae use haptoral hooklets to attach to a newly invaded host. The adult haptor often also has one or two pairs of larger hooks called hamuli for firm attachment to host epithelial cells. Adults in some families may have additional tiny sclerites resembling teeth, studs and/or spines for extra grip.

Arrangement, morphology and origin of sclerotised haptoral elements are important for classification, systematics and identification. The monopisthocotylean haptor can: form a muscular sucker supplemented by sclerites (e.g. Capsalidae); be divided into partitions called loculi each able to generate suction (e.g. Monocotylidae, some Capsalidae); have gland cells that secrete adhesives (e.g. Microbothriidae, Udonellidae, Anoplodiscidae); comprise sclerites and adhesives combined (e.g. Dactylogyridae). Unlike Polyopishtocotylea, Monopisthocotylea have no haptoral clamps. Monopisthocotylea also have anterior organs for attachment to hosts. Alternate use of haptor and anterior attachment organs permits leech-like movement over host epithelial cells despite strong shear forces from water flow as hosts swim and respire (Whittington, 2005).

The incredible diversity of Monopisthocotylea in form, function and structure of haptor and anterior attachment organs is matched by broad diversity in body plan (see Whittington 2005).

In Australia, 11 monopisthocotylean families are represented comprising 75 genera.

General References

Whittington, I.D. 2005. Monogenea Monopisthocotylea (ectoparasitic flukes). pp. 63-72 in Rohde, K. (ed.). Marine Parasitology. Collingwood, Victoria : CSIRO Publishing 592 pp. [63]

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