Life Cycle

Till now not much extensive studies on Phasmarhabditis has been done, however, whatever the little information available indicates that life cycle of this nematode is dependent upon the slug species it encounters. Researchers have described three distinct life cycles of Phasmarhaditis sp.

1. Saprobolic - Where the nematodes have been reared on rotting flesh (Maupas 1900), on slug faeces (Tan and Grewal 2001) or on a wide range of bacteria (Wilson et al. 1995). Tan and Grewal (2001a) have the opinion that this nematode can be exploited for long-term inoculative slug control as it can persist in the environment without the living hosts. Recently, Rae et al. (2006) in an experiment found that Pp. hermaphrodita strongly attracted to dead slug Deroceras reticula-tum than the live one, which adds weight to the hypothesis that this nematode is a facultative parasite capable of growing and reproducing on decaying plant and animal materials present in soil.

2. Necromenic - The infective juveniles of Phasmarhabditis get entrance into a slug, remain there without further development till the slug dies (Mengert 1953). After this infective juveniles feed on the slug cadaver, develop and reproduce. When the food starts depleting the formation of new infective juveniles takes place. These infective juveniles can be found in the mantle cavity, the general body cavity or the digestive tract of slugs. However, the entrance of nematode into slug and completion of life cycle there is parasitic or necromenic is still not fully understood (Wilson and Grewal 2005).

3. Parasitic life cycle: The infective juveniles enter into slug through the dorsal integumental pouch, through a short canal and reaches into the slug's shell cavity below the mantle (Wilson et al. 1993b; Tan and Grewal 2001). The development and reproduction of nematode takes place inside the slug. The infection in slug causes swelling of the rear half of the mantle where the nematodes reproduce. On an average 250-300 offspring of nematode is produced and once the second generation is produced these offspring spread throughout the slug's body and develop. The slug dies and third-generation nematodes are produced, which feeds on slug cadaver. When the food supply begins to deplete formation of infective juveniles takes place. Although the death of host generally occurs between 4 and 21 days, from the very time after infection the slug feeding is stopped (Glen et al. 2000; Grewal et al. 2001, Grewal et al. 2003).

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