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Title: PREVALENCE OF THELOHANIA SOLENOPSAE INFECTED SOLENOPSIS INVICTA NEWLY MATED QUEENS WITHIN AREAS OF DIFFERING SOCIAL FORM DISTRIBUTIONS

Author
item Preston, Catherine
item FRITZ, GARY - EASTERN ILLINOIS UNIV
item Vander Meer, Robert - Bob

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2006
Publication Date: 10/2/2006
Citation: Preston, C.A., Fritz, G.N., Vander Meer, R.K. 2006. Prevalence of Thelohania solenopsae infected Solenopsis invicta newly mated queens within areas of differing social form distributions. Journal of Invertebrate Pathology. 94(2):119-124.

Interpretive Summary: Biological control efforts aimed at managing the red imported fire ant include both the release of decapitating phorid fly parasites and pathogens, including a recently discovered virus, that have detrimental effects on the health of fire ant colonies. Field or laboratory-based research in areas unrelated to parasites and pathogens have assumed that colonies, often collected from the field or initiated in the laboratory using new fire ant queens, are healthy. Therefore, the increasing prevalence of diseased or parasitized colonies can have a confounding and negative impact on the interpretation of experimental results. In order to compensate for possible diseased colonies it is necessary to know the prevalence of the disease. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida, and the Department of Biological Sciences at Eastern Illinois University at Charleston, Illinois, examined the infection levels of a fire ant disease, Thelohania solenopsae, in newly mated queens (NMQs) from two social types, monogyne (single queen per mound) and polygyne (many queens per mound). The NMQs were collected from monogyne prevalent Gainesville and polygyne prevalent Ocala, Florida. We found that infection levels were lower in Gainesville than Ocala, averaging 1.67% and 14.14%, respectively. Polygyne NMQs collected in Ocala had the highest infection levels, 25.37% in 2003 and 21.43% in 2004. This information will be useful in future experimental designs and highlights the need to consider potential parasites and pathogens when collecting fire ant colonies for research.

Technical Abstract: Newly mated queens (NMQs) originating from monogyne red imported fire ant (Solenopsis invicta) colonies and following a mating flight, initiate new colonies by sealing themselves in a nuptial chamber and using stored food reserves to rear their first workers (claustral colony foundation). This method of colony founding is rarely successful for polygyne-derived NMQs, whose low weight critically limits the number of first workers produced. However, this observation may be confounded by the parasitic microsporidium, Thelohania solenopsae, thus far predominately found in association with polygyne colonies. This microsporidium reduces fat reserves within infected queens and may explain why polygyne NMQs are unable to found colonies claustrally. We collected NMQs following mating flights in Gainesville and Ocala, Florida. Newly mated queens were sorted by weight class, checked for insemination and T. solenopsae infection. Insemination levels were greater than 90% for all weight classes at both collection sites and were not related to infection. Infection levels were lower in Gainesville than Ocala, averaging 1.67% and 14.14%, respectively. Polygyne-derived NMQs collected in Ocala, defined here as weighing ' 12 mg, had the highest infection levels, 25.37% (17/67) in 2003 and 21.43% (6/28) in 2004. Therefore, infection by T. solenopsae cannot be completely responsible for the inability of polygyne NMQs to claustrally establish colonies. This work highlights the need to consider potential parasites and pathogens when collecting fire ant colonies for research.