Mermithid Infection Research Articles

Observations on the occurrence and collection of mermithid nematodes from blackflies (Diptera: Simuliidae).

From 1973 through 1975 larval blackflies were sampled for mermithid nematodes in 83 streams in Newfoundland. Prosimulium mixtum/fuscum and Simulium venustum were the predominant hosts of the mermithid Neomesomermis flumenalis but rates of infection in late-instar larvae were generally low (4.3 ± 0.7% and 5.4 ± 1.2% for P. mixtum/fuscum and S. venustum respectively). Mermithid infection in the streams studied showed temporal fluctuations and varied among and within host breeding sites. When numbers of parasitized larvae were judged adequate, mass collections of larvae were made and held in the laboratory for emergence of mermithids. Nematode emergence was in two distinct peaks, one for the Prosimulium generation the other for the first generation of S. venustum. The temporal separation of the peaks varied from year to year owing to weather. Observations on the bionomics of both mermithids and blackfly hosts made during the course of the surveys and technical problems inherent to such studies are discussed.

Some effects of mermithid infection on metabolic reserves and flight in Locusta

Low infections of Mermis nigrescens reduce the flight performance of adult male Locusta migratoria, and bring about changes in the levels of blood carbohydrate and protein but not lipid. The quantities of all three metabolites in the fat body are reduced, as is the amount of tissue present. Lipid content only, is markedly decreased in the flight muscle, but the water content is increased. Blood volume and malpighian tubule activity are unaffected by mermithid infection, but the rates of lipid mobilisation in response to injections of extracts of corpora cardiaca or flight are greatly reduced compared with those in uninfected locusts. Additional carbohydrate does not correct flight performance in parasitised locusts as it does in starved animals. Poor flight performance is not due to an effect of the worm on the host endocrine system.

Ecology of Simuliidae, Mermithidae, and Microsporida in Newfoundland freshwaters.

Prosimulium mixtum/fuscum S. &D., Cnephia mutata (Malloch), C. dacotensis D. &S., Simulium aureum Fries, and S. gouldingi Stone are univoltine. S. venustum Say, S. vittatum Zett., S. tuberosum (Lundstrom), S. corbis Twinn, S. latipes (Mg.), and S. decorum Walker are multivoltine. Neomesomermis flumenalis (Welch), Gastromermis viridis Welch, and Isomermis wisconsinensis Welch are univoltine. The eggs of Prosimulium and Cnephia species hatched synchronously with a batch of the eggs of N. flumenalis. The eggs of the first generation of Simulium species hatched synchronously with the eggs of G. viridis and I. wisconsinensis, and the overwintered batch of eggs of N. flumenalis. The larvae of subsequent generations of Simulium species were not infected by mermithids. Mermithid infections occur during the hatching and buildup of blackfly larval population.Caudospora simulii Weiser and C. brevicauda Jamn. occur in Prosimulium and Cnephia species during the cold seasons. Thelohania bracteata (Strickland, 1913), Pleistophora simulii (Lutz and Splendor, 1904), P. multispora (Strickland, 1913), and Coelomycidium simulii Debaisieux occur in Simulium species during the warm seasons. G. viridis and I. wisconsinensis overwinters in the egg stage, and N. flumenalis overwinters partly in the egg stage and partly as parasites in P. mixtum/fuscum. S. venustum and P. mixtum/fuscum are the most prevalent and abundant of the simuliids. N. flumenalis is the most prevalent and abundant of the mermithids and P. multispora is the most abundant of the microsporidans. Aeshna interrupta Walker and Rhyacophila fuscula (Walker) prey on S. venustum larvae.