''Cyclocotyla'' is a genus of

monogenea Monogeneans 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 have both male and female reprod ...

flatworm The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegment ...

s first described in 1821. It currently consists of one valid species, ''Cyclocotyla bellones'', with all other former members reassigned to other genera. However, some consider that the genus is currently a ''

taxon inquirendum In biological classification, a ''species inquirenda'' is a species of doubtful identity requiring further investigation. The use of the term in English-language biological literature dates back to at least the early nineteenth century. The term t ...

''. The sole species ''C. bellones'' is notorious for being a

hyperparasite A hyperparasite, also known as a metaparasite, is a parasite whose host, often an insect, is also a parasite, often specifically a parasitoid. Hyperparasites are found mainly among the wasp-waisted Apocrita within the Hymenoptera, and in two othe ...

. It dwells on the

isopod Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...

parasite ''

Ceratothoa ''Ceratothoa'' is a genus of isopod ectoparasites of teleost fish, first described by James Dwight Dana in 1852. Infection by ''Ceratothoa'' can cause anaemia, lesions, growth retardation, emaciation, and mortality in their fish hosts. Specie ...

parallela'' (among others of the same genus), which itself feeds on the fish ''

Boops boops ''Boops boops'' (; from Ancient Greek , literally 'cow-eye'), commonly called the bogue, is a species of seabream native to the eastern Atlantic. Its common name in most languages refers to its large ("bug") eyes. Distribution and habitat The sp ...

'' and ''

Pagellus acarne ''Pagellus acarne'' is a species of fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various ...

''. However, in a 2022 study, it was found that the species was not truly an hyperparasite, since it did not feed on the crustacean but rather on the fish. The authors concluded "''Cyclocotyla bellones'' is thus both an

epibiont An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An epi ...

on the crustacean and a parasite of the fish. It could be considered a hyperparasite only in terms of location (it dwells on a parasite), but not in terms of nutrition (it does not feed on a parasite but on a host which is not a parasite)."

References

Animals described in 1823 Diclidophoridae {{Monogenea-stub