Ophryocystis elektroscirrha
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| Ophryocystis elektroscirrha McLaughlin & Myers, 1970 |
Ophryocystis elektroscirrha is an obligate, neogregarine protozoan that infects monarch (Danaus plexippus) and queen (Danaus gilippus) butterflies. There are no other known hosts. The species was first discovered in Florida, around the late 1960s.[1]. Since then, it has been found in every monarch population in the world. Because of this, it is thought that O. elektroscirrha and monarchs are an example of coevolution.
Dormant spores occur on the cuticles of butterflies, in between the butterfly's scales. They are small, brown or black objects about 1/100th of a butterfly scale.
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[edit] Life cycle
O. elektroscirrha is usually transmitted from females to their offspring when the females scatter spores on milkweed, the host plant of monarchs and queens, during ovoposition, the process of laying eggs. The spores are then eaten by the larvae while they feed on leaves. Once in the gut, the spores germinate and migrate to the hypoderm (the layer of cells that secrete the cuticle), where they undergo two phases of vegetative reproduction. After the caterpillar pupates, O. elektroscirrha starts reproducing sexually. Three days before the adults emerge, spores can be seen through the pupal integument. The adult butterflies emerge covered with spores, mostly on their abdomens. Once the adults emerge, the parasites have already done all the physical damage and they do not continue reproducing.
[edit] Effect on the butterfly population
Because O. elektroscirrha is present in every monarch population, it is thought to be an example of coevolution. Therefore, monarchs and queen butterflies have evolved alongside OE and have developed natural defenses against it. In a study designed to test the effects of OE on the survival and reproduction of monarchs except at the highest dose they tested, which was 1000 spores per larva. Those with such densities had decreased survival and eclosion (emergence from pupae) smaller wingspans, and lower body masses than adults that had not been inoculated. This was especially true if they were inoculated at an earlier stage. It was also found that male lifespan and reproductive success was decreased with the highest dose, while females did not have a significant decline in lifetime fecundity, although the females in outdoor eclosures were less active than uninfected females.
Among the adult populations in nature, parasite density was associated with butterfly condition and activity. In western North America and Florida, those which were infected with a high dose of OE were smaller than uninfected monarchs, while overwintering adults in Mexico and California, mating activity was positively associated with higher parasite loads. Intermediate spore loads had more wing tatter and scale loss than those with no spores.
While size decreased and wing tatter and scale loss increased, the study found that they did not have a big impact on the survival and reproduction of monarch butterflies, which is consistent with the idea that parasites transmitted through the mother should not have a great effect on host fitness compared with horizontally transmitted parasites.
[edit] References
- ^ R. E. McLaughlin & J. Myers (1970). "Ophryocystis elektroscirrha sp. n. a neogregarine pathogen of the monarch butterfly Danaus plexippus (L.) and the Florida queen butterfly Danaus gilippus berenice Cramer". Journal of Protozoology 17: 300–305.
