Parasites and Natural Enemies: Life Cycle of O. elektroscirrha

Background and Life Cycle of Ophryocystis elektroscirrha

Ophryocystis elektroscirrha is a protozoan parasite that was first recovered from monarch and queen butterflies in Florida in 1966 (McLaughlin and Myers 1970).  New infections occur when larvae ingest parasite spores as they feed on contaminated egg shells or milkweed leaves.   Most spores are transmitted from infected adults to their offspring (vertical transmission), although horizontal transmission may also occur.  Following ingestion, spores lyse in larval guts. Emerging sporozoites then penetrate the intestinal wall, enter the hypoderm, and undergo two phases of vegetative, asexual replication. After host pupation, the parasite undergoes sexual reproduction and forms dormant spores around the scales of the developing adult butterfly (McLaughlin and Myers 1970). Most spores form on the adult abdomen, although spores also develop on the wings, head, and thorax (Leong et. al. 1992; S.M. Altizer, personal observation).

Life Cycle of O. elektroscirrha

Heavily infected adults have difficulty emerging from their pupal cases and expanding their wings, although adults with low parasite loads appear normal (McLaughlin and Myers 1970; Leong et al. 1992). High parasite doses decrease larval survivorship from hatching to eclosion, and heavily captive adults are smaller and shorter-lived than uninfected adults (Altizer and Oberhauser 1999).

Clusters of O. electroscirrha spores form dark blotches under the cuticle of developing pupae (L) about 3 days before eclosion.  A monarch dissected out of its pupal case (R) shows that most spores form in the abdomen of infected butterflies.

Heavily infected captive monarchs (L) often are too weak to emerge from their pupal cases or expand their wings.  Spores of O. electroscirrha (R) appear as small brown ovals next to the larger butterfly scales.

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References

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Altizer, S. and Oberhauser, K. 1999.  Effects of the protozoan parasite, Ophryocystis elektroscirrha, on the fitness of monarch butterflies (Danaus plexippus).   Journal of Invertebrate Pathology.  In press.

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Leong KLH.  Kaya H.K. Yoshimura M.A. Frey D.F. 1992.  The occurrence and effect of a protozoan parasite Ophryocystis elektroscirrha (Neogregarinida: Ophryocystidae) on overwintering monarch butterflies Danaus plexippus (Lepidoptera: Danaidae) from two California winter sites.  Ecological Entomology 17(4).  338-342.

Leong KLH. Yoshimura M.A. Kaya H.K. and Williams, H.  1997.  Instar susceptibility of the monarch butterfly (Danaus plexippus) to the neogregarine parasite, Ophryocystis elektroscirrha.  Journal of Invertebrate Pathology.   69(1) 79-83.

McLaughlin, R.E. and Myers, J.  1970.  Ophryocystis elektroscirrha sp. n. a neogregarine pathogen of the monarch butterfly Danaus plexippus (L.) and the Florida quen butterfly Danaus gilippus berenice Cramer.  Journal of Protozoology. 17. 300-305.

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Urquhart, F.A. 1987.  The Monarch Butterfly: International Traveler.   Nelson-Hall, Chicago, IL. 232 pp.

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