Entomopathogenic Nematode - Life Cycle

Life Cycle

Since they are economically important, the life cycles of the genera Heterorhabditidae and Steinernematidae are particularly well known. Although not closely related, phylogenetically, both share similar life histories (Poinar 1993). The cycle begins with an infective juvenile, whose only function is to seek out and infect new hosts. After entering an insect, infective juveniles release an associated mutualistic bacterium. These bacteria of the genus Xenorhabdus or Photorhabdus, for steinerernematides and heterorhabditids, respectively—cause host mortality within 48 hours. The nematodes provide shelter to the bacteria, which, in return, kill the insect host and provide nutrients to the nematode. Together, the nematodes and bacteria feed on the liquefying host, and reproduce for several generations inside the cadaver. Steinernematid infective juveniles may become males or females, whereas heterorhabditids develop into self-fertilizing hermaphrodites with later generations producing two sexes. When food resources in the host become scarce, the adults produce new infective juveniles adapted to withstand the outside environment. After about a week, hundreds of thousands of infective juveniles emerge and leave in search of new hosts, carrying with them an inoculation of mutualistic bacteria, received from the internal host environment (Boemare 2002, Gaugler 2006).