|
|
 |
Females:
Diovarial, amphidelphic
|
|
Older female with eggs hatching in uteri
 |
|
|
Males: Showing testis,
spicules and gubernaculum |
|
 |
Photomicrographs by Howard Ferris
Nematodes from an organic vegetable
production system, Salinas, California
|
|
Male tail: spicules, gubernaculum, testis, spermatocytes |
 |
|
 |
|
|
|
|
|
|
|
Pristionchus spp.
have cellulases, presumably through horizontal transfer from microbes (Smant,
1998).
Unlike the rhabditids,
Pristionchus and other diplogasterids
do not have a
grinder in the basal bulb of the esophagus, so there are living
bacteria in the intestine.
The mouth also differs from the tubular stoma of the
rhabditids and has two forms, with teeth (eurystomatous) or without teeth (stenostomatous).
Tooth formation is triggered by starvation, similar to the dauer trigger
in C. elegans.
Pristionchus can feed on different food sources. Stenatostomous worms
can feed on bacteria while eurystomatous
Pristionchus can feed on fungi, other organic material and even prey on other nematodes.
Dauerlarva formation occurs under conditions of high
nematode density and low food availability, similar to
C. elegans.
Sommer et al (2008) separate
species based on one nucleotide difference.
Mating occurs if difference is < 1 nucleotide, fails if > 1 nucleotide.
The nematode—insect association, in which nematodes infest the
surface of insects and wait for their associated insect to die before resuming development
on the cadaver, is known as necromeny (Hong et al, 2008).
Pristionchus nematodes infest live insects but do not noticeably
reduce the fitness of their insect associate but consume the microorganisms on the
decomposing carcass after death of the insect.
Developmental phenomena such as formation of dauer
larvae formation, and different forms of the mouth can be influenced by changes
in temperature and food availability to the host insect. (Hong et al., 2008).
The dauerlarva invades the insect, waits for insect death
and then feeds on decomposing microbes — a
necromeny association.
Necromeny may be a pre-adaptation in the evolution of
parasitism.
Each nematode species is able to detect its corresponding beetle by
olfactory signals and the nematodes are attracted to the sex pheromones of the
beetles.