Nematode Bacteria Association

The research on the association of slug-parasitic nematode, Pp. hermaphrodita with bacteria has not been carried out extensively as like entomopathogenic nematodes; therefore, a meagre information is available on this aspect. Tan and Grewal (2001b) on the basis of an experiment reported that Pp. hermaphrodita acts as a vector to transport the bacteria Moraxella osloensis into the shell cavity of the grey garden slug, Derocerus reticulatum. The infective juveniles of the nematode move through the soil, locate and infect the slug by penetrating through a natural opening at the backside of the mantle. Once inside the body of the host the infective juveniles release bacterial cells, start feeding on multiplying bacteria and develop into self-fertilizing hermaphrodites. This nematode-bacterial complex can cause the death of slug within 7-21 days after infection. Wilson (2002) reported association of

Pp. hermaphrodita with several bacterial isolates. In an experiment highest yield of Pp. hermaphrodita was obtained when cultured with the bacteria, Providencia rettgeri, M. osloensis (Wilson et al. 1995a) and two isolates of Pp. fluorescens. When a bioassay was conducted with these nematode-bacterial isolates against the slug D. reticulatum only, M. osloensis and Pp. flourescens were found to be pathogenic (Wilson et al. 1995b). However, no highly specific mutualistic association of Pp. hermaphrodita with bacteria has been found. Wilson and Grewal (2005) is of the opinion that lack of bacterial specificity as a food source as well as lack of a rigid cuticle in slugs indicate that more or less there is a general association of bacteria with Pp. hermaphrodita. It has been observed by researchers that the bacteria M. osloensis kill slugs only when they are carried by infective juveniles of nematodes (Tan and Grewal 2001b). New infective juveniles carry more viable cells of M. osloensis than the older one (Tan and Grewal 2001b). Tan and Grewal (2002) reported that M. osloensis produces a heat-stable endotoxin, which consists of a lipopolysaccharide lethal to slugs.

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