''Cystidicoloides tenuissima'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

s in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Spirurida Spirurida is an order of spirurian nematodes. Like all nematodes, they have neither a circulatory nor a respiratory system. Some Spirurida, like the genus ''Gongylonema'', can cause disease in humans. One such disease is a skin infection with ...

and family Cystidicolidae. It is a parasite of salmonid fish (salmon, trout and their allies) in the northern hemisphere and has

mayflies Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the orde ...

as the alternate

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

Ecology

Adult ''Cystidicoloides tenuissima'' are found in the stomachs of salmonid fish. The fish, mostly trout and juvenile salmon, acquire the worms by feeding on infected

which are the alternate hosts of the parasite. In the

River Swincombe The River Swincombe is a tributary of the West Dart River that flows through Dartmoor national park in Devon, south-west England. It rises south-east of Princetown, and flows 2 km south-east to Foxtor Mires, where it turns north-east to me ...

in England, the only mayfly in which the parasite develops is the sepia dun (''

Leptophlebia marginata ''Leptophlebia marginata'', the sepia dun, is a species of mayfly in the family Leptophlebiidae. It is native to Europe and North America where it is distributed widely near lakes, ponds and slow-moving streams. The larvae, which are known as ny ...

''). In Czechoslovakia, nymphs of ''

Ephemera danica ''Ephemera danica'', the green drake or green drake mayfly, is a species of mayfly in the genus '' Ephemera''. Description ''Ephemera danica'' can reach an imago size of in males, while females are larger, reaching . This mayfly, with its cha ...

'', '' Habrophlebia lauta'' and '' Habrophlebiodes modesta'' were found to be capable of transmitting infection, and the larvae were found to be able to survive into the winged adult mayfly stage. When the

stone loach The stone loach (''Barbatula barbatula'') is a European species of fresh water ray-finned fish in the family Nemacheilidae. It is one of nineteen species in the genus ''Barbatula''. Stone loaches live amongst the gravel and stones of fast flowin ...

(''Barbatula barbatula''), a fish in the family

Balitoridae The hillstream loaches or river loaches are a family, the Balitoridae, of small fish from South, Southeast and East Asia. The family includes about 202 species. They are sometimes sold as "lizardfish" or (in Germany) "flossensaugers". Many of the ...

, was experimentally infected, the nematodes did not develop beyond the fourth larval stage. ''C. tenuissima'' is an annual parasite of fish, with the maturation of the nematode being correlated with the temperature of the water. Adult worms lay eggs in summer and autumn and these pass out of the fish. The eggs form part of the diet of many aqueous invertebrates but it is only when they are eaten by developing

nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...

of mayflies that they can continue their life cycle. The juvenile worms live in the body cavities of the nymphs which soon become infective to fish. Fish feed relatively little on early-stage mayfly nymphs during the summer but increasingly consume them as the nymphs grow larger in autumn and winter. Peak incidence of parasitism in fish is in the spring; thereafter the incidence rapidly falls, this being the period when the adult nematodes lay eggs, after which the worms die.

References

{{Taxonbar, from=Q10465200 Spirurida Parasitic nematodes of fish Nematodes described in 1800