Authors

Discussion

Polystomatid flatworms (Monogenea: Polystomatidae) are globally distributed parasites. Currently, there are 30 recognised genera comprising of more than 180 species. The vast majority (20 genera) are associated with amphibian hosts with one genus known from caecilians, two from salamanders and 17 from frogs. One genus is described from a dipnoan fish, eight from chelonians and one from a mammal. Based on molecular analyses, not all of the currently recognised genera are monophyletic and a few clusters remain unresolved.

Polystomatids display a variety of life history strategies with deep evolutionary origins. In terms of diet, the amphibian polystomatids are sanguinivorous while the remainder are mucophagic. There is also considerable variability in infection site, although none of the representatives of this family are truly endoparasitic. In frogs and caecilians, mature polystomatids are found in the urinary bladder. Conversely, they are found on the external gills or in the oral region of salamanders. The genus known from the Australian lungfish is also found in the oral region. The greatest diversity is known from freshwater chelonians, where polystomatids are found in the oral region including the nasal passages and pharyngeal pouches, in the urinary bladder, accessary bladders and the cloaca, and on the eyes. Finally, the sole species known from a mammal infects the eye of the hippopotamus.

The present study explored the unique features and adaptations that enable these parasites to survive in their respective microhabitats with regards to the evolutionary relationships within the group.