Analysis of two isolates of a Heterorhabditis bacteriophora population detected in Córdoba, Argentina

Abstract

AbstractEntomopathogenic nematodes of the genus Heterorhabditis are associated with symbiotic bacteria Photorhabdus spp. (Enterobacteriaceae). Taxonomic studies confirm that each species of nematode has a specific natural association with only one species of bacterium (Boemare & Doucet, 1996). Except in a few cases, the bacteria change the colour of the parasitized insect to different reddish tones and produce bioluminescence (Grimont et al., 1984; Boemare & Doucet, 1996). These distinct colours would be assumed to be due to the different species of Photorhabdus and, consequently, to indicate different species of Heterorhabditis. Therefore, the colour of the cadaver has been used as a taxonomic character (Stock, 1993). In a single soil sample from Córdoba City, Argentina, two isolates of Heterorhabditis were found that were clearly distinguished by the colour of the parasitized Galleria mellonella larva: isolate A, violet-brown; B, reddish. These different phenotypes led us to suppose that the nematode isolates were associated with different symbiotic bacteria and that the nematodes were different species. The purposes of this work were: to establish the identity of the isolates and to compare them on the basis of morphological and morphometric characters, and isozyme patterns.