Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/1999
Publication Date: N/A
Interpretive Summary: Several microsporidia cause significant mortality in fire ants in South America and are being evaluated as potential biological control agents of imported fire ants in the United States. Recently, a microsporidium has been found for the first time in red imported fire ants in the United States. Light-microscopic examination cannot differentiate this isolate from the isolates found in the South American ants. In this study, scientists at the Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida compared ultrastructural and molecular characteristics of the isolates from the United States and South America to determine their taxonomic relationship. Spore ultrastructure and the 16S ribosomal gene sequence of the US isolate were determined and compared to those of the South American isolates. The results support light-microscopic evidence that the different isolates are very closely related and should be considered members of a species complex. This information is necessary for designing a biological control strategy of imported fire ants in the United States utilizing these important natural control agents.
Technical Abstract: The Thelohania solenopsae complex is composed of species from 2 different fire ant hosts and 3 localities: T. solenopsae from the red imported fire ant Solenopsis invicta (type host)(Brazil), Thelohania sp. from the black imported fire ant S. richteri (Argentina), and Thelohania sp. from S. invicta (US). The sequence of the 16SrRNA gene of thelohania sp. (US) was determined and compared to those of T. solenopsae (Brazil) and Thelohania sp. (Argentina). The sequence of Thelohania sp. (Argentina)(98.9% sequence identity), supporting light-microscopic and ultrastructural evidence that Thelohania sp. (US) is closely related to the isolates form Brazilian and Argentinean fire ants. We propose - until additional information is available - to refer to the different isolates of the T. solenopsae complex as T. solenopsae (Brazil), T. solenopsae (Argentina) and T. Solenopsae (US). These fire ant microsporidia are the only hymenopteran microsporidia investigated extensively as potential biocontrol agents. A listing of all hymenopterous hosts for microsporidia is provided.