Agriculture Reference
In-Depth Information
Reproduction is either amphimictic or parthenogenetic. Nematodes produce eggs and
most larvae reach the adult stage in
ca.
20 days (5 to 50), after four stages separated by
moulting of the cuticle (Kühnelt, 1961). However, significant differences occur between
free-living nematodes which become adult in
ca.
eight days, and phytoparasitic species
which have much longer cycles of
ca.
30 days. The length of the development period
may be significantly influenced by temperature conditions (Norton, 1978).
Nematodes progress by undulatory movements and crawl in thin films or swim in
thicker ones. Unable to move soil particles, they are restricted to pores and capillaries of
a diameter larger than their own. The presence of solid particles may be essential to their
growth although they can sometimes be bred in agar or liquid media (Cheng
et al.,
1979).
Basically, all nematodes feed on living protoplasm, including the cell contents of
plants, bacteria, microscropic algae, protists, small Metazoa or plant sap. Their simple
digestive systems do not permit assimilation of decomposing material that is not readily
assimilable. They often have chitinous stylets, spears or buccal armatures that they use to
pierce living cells; cell contents are ingested by a muscular pharynx, which acts as a pump
(Figure III.28).
