Geoscience Reference
In-Depth Information
cially on plant tissues - to those that burrow deeply into roots and create cavities with-
in them. The most specialized forms are found in the family Heteroderidae in which
the sedentary females become swollen and flask-shaped and scarcely recognizable
as eelworms at all. The typical vermiform males are sometimes rare or absent. Even
when present they may be unnecessary for fertilization because, in some species, new
generations are produced parthenogenetically.
F
IG. 37
Potato root eelworm
Globodera rostochiensis;
developing females and cysts on potato roots. (Photograph
K. Evans.)
The root-knot eelworms of the genus
Meloidogyne
are so called because they
produce gall-like growths in the tissues they attack. The females become firmly em-
bedded in the root, and the eggs are laid into a gelatinous sac where they can survive
for over a year in the soil. They are mainly tropical species attacking important crops
such as tea, coffee, peanut, tobacco and sugar-cane as well as vegetables and cereals.
The cyst-forming nematodes of the genus
Heterodera
take this life style a stage
further. The eggs are retained within the body of the female which becomes a tough
