Description and development of Gastromermis anisotis sp n. (Nematoda : Mermithidae), a parasite in a quadritrophic system involving a cyanobacterium, midge and virus

摘要

This paper reports the results of a 25 year study on an obligate quadritrophic system involving a midge, Cricotopus nostocicola (Diptera: Chironomidae), its cyanobacterial food source, Nostoc parmeliodes (Nostocales), a new species of nematode parasite of the midge, Gastromermis anisotis sp. n. (Mermithidae), and a virus infecting the nematode. Occurring in a mountain stream in California. the components of this system are adapted for survival at temperatures just above freezing (4-8degreesC). Developmental studies of the nematode include mating, oviposition, egg hatch, host penetration, parasitic development, free-living habits, spermatogenesis, platelet structure. and virus infection. Rates of parasitism varied between 5-42% over the 25 year period. The nematode was considered to be the most significant biological control agent of Cricotopus populations in the stream.