Wolbachia spp.
Jennifer Parks

SEX AND SEXUALITY: WOLBACHIA SPP. IN INSECT REPRODUCTIVE MECHANISMS

Wolbachia spp. is a gram-negative bacteria that is an intracellular parasite that is carried in about 20% of insects and arthropods. This bacteria invades the testes or ovaries and dramatically alters the reproductive future of its hosts. It has been called "widow maker" since it dramatically decreases the role of males in sexual reproduction of infected insects. Passed on to the offspring, it has serious implications in the evolution of certain insect species. A study done in two-spot ladybugs showed that infected females hatch roughly about half of the usual number of eggs, but that the resulting offspring is virtually all female; Wolbachia strangles the males before birth. In some insect species, infected males can only mate successfully with infected females; in others, males are not needed at all, for the females are fertilized via parthenogenesis. In one arthropod species that was studied, Wolbachia has even been shown to transform male embryos into females. Generally, if an infected male mates with an uninfected female, cytoplasmic incompatibility causes few or no offspring to hatch.

An interesting exception to the "no male" rule is in jewel wasps. In instances where infected males mate with uninfected females, only male progeny are produced. This leads to the propagation of the bacterial infection, since it reduces the number of uninfected females in the wasp population and introduces infected males. Of course, it works the same way with the male-killing examples, with only infected females being born and few or no infected males.

Antibiotics have been used to get rid of Wolbachia infections. With treatment, insects can
be bacteria-free in just a few generations.

But this bacteria doesn't just affect bugs. It has been found that river blindness, prevalent in Africa and South America, is in fact caused by Wolbachia and not the parasitic worms that have been blamed in years past. Tests done on mice showed that rodents infected with regular worms did not exhibit severe symptoms, yet ones that received worms infected with the Wolbachia bacteria did. This is one case in which antibiotics are most likely going to be used to fight the infections.

References

1. "About Wolbachia."
<http://www.wolbachia.sols.uq.edu.au/about.cfm>
(January 15, 2003).

2. "Africa: One Step Nearer to Cure for River Blindness."
<http://www.irinnews.org/report.asp?ReportID=24679&SelectRegion=Africa&SelectCountry=AFRICA>
(January 15, 2003).

3. Gee, Henry. "Wolbachia, Widowmaker." Nature Science Update.
<http://www.nature.com/nsu/990429/990429-8.html>
(January 15, 2003).

4. Travis, John. "Undesireable Sex Partners." Science News Online, November 16, 1996.
<http://www.sciencenews.org/sn_arch/11_16_96/bob1.htm> (January 15, 2003).
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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