l
The IJ leaves the pathogenic phase in a growth stage that is
known as recovery and changes into the fourth stage (J4) and
then the first-generation adults.
l
J4 stage nematodes mature into egg laying female or male adults
in the insect cadaver and with this undergo four juvenile stages
(J1–J4) and the adult stage has up to three generations [1].
l
Steinernematid IJs develop into males or females in all successive
generations, while heterorhabditids become self-fertilizing hermaphrodite females in the first generation, and in subsequent
generations develop into amphimictic males and females or into
automictic
hermaphrodite,
or
both
can
happen
concurrently [96].
l
Therefore, in general, the two nematodes steinernematids and
heterorhabditids differ slightly in their reproduction in the host
insect. If it is Steinernema, it needs two individuals, one male and
one female, to be present in the insect host before they can
reproduce, whereas for a Heterorhabditis, a single IJ is enough
to invade a host insect to reproduce and develop [97].
l
The progeny of the first-generation adults evolves either
through all the four juvenile stages to the second-generation
adults or into third-stage IJ, depending primarily on the availability of nutrition and density of population.
l
Several hundred thousands of new generation IJs are developed
depending on the size of the insect prey in around 2 weeks from
a single insect cadaver.
l
After two to three reproduction cycles and depletion of all the
nutrition in the cadaver, an increased population density of
nematodes triggers their development into IJs again.
l
The infective juvenile nematodes re-associate with bacterial symbionts and reinitiate the symbiosis.
l
Finally, the IJs emerge from the empty insect carcass into the soil
environment from where they can locate and invade the next
insect hosts.
l
The life cycle of EPNs from infective juvenile penetration to
infective juvenile emergence is completed within 6–11 days for
Steinernematids and 12–14 days for Heterorhabditids [98].
l
Growth of nematode under optimum conditions (soil temperatures 77–82 ºF) takes about 3–7 days for one life cycle from egg
to egg inside an insect host (Fig. 1) [99].
Life Cycle
21
The IJ leaves the pathogenic phase in a growth stage that is
known as recovery and changes into the fourth stage (J4) and
then the first-generation adults.
l
J4 stage nematodes mature into egg laying female or male adults
in the insect cadaver and with this undergo four juvenile stages
(J1–J4) and the adult stage has up to three generations [1].
l
Steinernematid IJs develop into males or females in all successive
generations, while heterorhabditids become self-fertilizing hermaphrodite females in the first generation, and in subsequent
generations develop into amphimictic males and females or into
automictic
hermaphrodite,
or
both
can
happen
concurrently [96].
l
Therefore, in general, the two nematodes steinernematids and
heterorhabditids differ slightly in their reproduction in the host
insect. If it is Steinernema, it needs two individuals, one male and
one female, to be present in the insect host before they can
reproduce, whereas for a Heterorhabditis, a single IJ is enough
to invade a host insect to reproduce and develop [97].
l
The progeny of the first-generation adults evolves either
through all the four juvenile stages to the second-generation
adults or into third-stage IJ, depending primarily on the availability of nutrition and density of population.
l
Several hundred thousands of new generation IJs are developed
depending on the size of the insect prey in around 2 weeks from
a single insect cadaver.
l
After two to three reproduction cycles and depletion of all the
nutrition in the cadaver, an increased population density of
nematodes triggers their development into IJs again.
l
The infective juvenile nematodes re-associate with bacterial symbionts and reinitiate the symbiosis.
l
Finally, the IJs emerge from the empty insect carcass into the soil
environment from where they can locate and invade the next
insect hosts.
l
The life cycle of EPNs from infective juvenile penetration to
infective juvenile emergence is completed within 6–11 days for
Steinernematids and 12–14 days for Heterorhabditids [98].
l
Growth of nematode under optimum conditions (soil temperatures 77–82 ºF) takes about 3–7 days for one life cycle from egg
to egg inside an insect host (Fig. 1) [99].
Life Cycle
21