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The Mode of Gregarine Infection in Zygoptera (Odonata)
Author(s) -
Åbro Arnold
Publication year - 1976
Publication title -
zoologica scripta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.204
H-Index - 64
eISSN - 1463-6409
pISSN - 0300-3256
DOI - 10.1111/j.1463-6409.1976.tb00708.x
Subject(s) - biology , odonata , chironomidae , ceratopogonidae , zoology , ecology , budding , woodland , host (biology) , predation , parasite hosting , intermediate host , larva , botany , world wide web , computer science
Åbro, A. (Institute of Anatomy, University of Bergen, N‐5000 Bergen, Norway). The mode of gregarine infection in Zygoptera (Odonata). Zool. Scr. 5 (6): 265–275, 1976.—The eugregarine Hoplorhynchus oligacanthus (Sieb.) is an intestinal parasite in imagines of the zygopterans Pyrrho‐soma nymphula (Sulz.) and Enallagma cyathigerum (Charp.). Gameto‐cysts, resulting from the union of a presumed male and a female gregarine gamont, leave the host with the faeces which drop to the woodland floor. Gametogony, zygote formation, and subsequent sporogony take place within the extrahost gametocysts. Infective sporozoites become enclosed in oocysts furnished with a highly resistent shell. When fully formed, the oocysts are released by simple rupture of the gametocyst envelopes. The oocysts, which probably disperse in the habitat by means of rain‐water, appear to enter a cryptobiotic state. Enzymic tests implied that liberation of sporozoites occurred more readily if oocysts were submitted to repeated freezing and thawing. Zygopterans consume lots of small insects; about three‐quarters of zygopteran food was found to consist of Chironomidae and Ceratopogonidae. Examination of various small insects available as prey for zygopterans revealed imagines of medium‐sized Chironomidae and Ceratopogonidae as vectors of Hoplorhynchus oocysts, which were found suspended on their tarsal bristles. An infective oocyst appears to contain 8 sporozoites. When introduced into a host, each of the sporozoites released from the oocyst will eventually develop into a gamont. Only one in a hundred chironomids and ceratopogonids was found to carry oocysts; none the less, this is considered sufficient to cause a high infection of the entire zygopteran populations. The occasional large number of non‐infective oocysts without sporozoites indicates that sporogony and formation of an oocyst capsule are independent events.