Natural occurrence of the fire ant nematode Allomermis solenopsii (Mermithidae) in Argentina and effect on worker ants

VARONE, LAURA; CABRERA, SONIA; BRIANO, JUAN A.

Charleston

Congreso; Imported Fire Ant Conference; 2008

Entomological Society of America

Mermithids have been reported several times from Neotropical ants. Only recently Allomermis solenopsii was described as new species from Solenopsis invicta colonies in Argentina (Poinar et al. 2007). Studies have been conducted at SABCL to determine occurence of Allomermis solenopsii and effect on worker ants, in order to evaluate the organism as biological control agent of Solenopsis spp. in the United States. The mechanism of entrance of the nematode to the host is unkwown, and the hyphotesis of entrance in earlier stages was supported by the finding of parasitized pupae. Five of the 21 surveyed sites were positive, with 37.6% of the colonies parasitized and 82 parasitized workers in each (range 1-411). Positive sites were revisited to monitor mermithid persistence. The infection persisted in all sites but the parasitization rate showed great variations. Survival of healthy and parasitized workers from 13 infected colonies was compared. Parasitized workers lived shorter. Stinging tests were conducted with 5 volunteers exposed for 10 minutes to 10 parasitized workers each. Parasitized workers did not sting and the typical gaster-curved sting position was not observed. Aggression tests are being conducted by confining two workers from different colonies. Most interactions between parasitized workers were not aggressive (n=69). Future plans include determination of the entrance mechanism of Allomermis to the ant host, estimation of the impact of Allomermis on fire ant colonies and determination of the causes for the lack of stinging behaviour.