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General Morphology of Nematodes
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Female Reproductive System
Female
Reproductive System
The main parts of the female reproductive
system are ovaries, which are tubular sac consisting of a germinal zone
where rapid cell divisions take place ; the growth zone where the
oogonia gradually increases in size; the oviduct which follows the ovary
and is a constricted thick walled region. The uterus is a broad tube.
The eggs are stored in the uterus. The beginnings of the uterus usually
function as a spermatheca or seminal receptacle. In some nematodes, a
slight enlargement in the proximal part of the oviduct serves as a
spermatheca or seminal recptacle. The uterus is covered also by a muscle
layer. The eggs, after fertilization and maturation, and to some extent
embryonic development also, pass out through the vaginal opening, the
vulva. The nematodes, with a single ovary, sometimes possess also the
rudiments of the second genital tube which may function as a spermatheca.
The rudimentary tube is known as a post-vulval uterine sac.
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Reproduction.
Males are important for
reproduction in the bisexual species. In such cases, the males are
as abundant as the
females in the
populations. In some species, the females can reproduce
parthenogenetically, as in genus Mehidogyne. In
these cases,
the nematode populations are either
devoid of males or if present, their number is small or the males
are degenerated type. The absence of males in the population or any
of the above possible conditions indicates a tendency towards
hermapbrcditism or parthenogenesis, in the latter case, there is
self-fertilization with the sperm, the eggs being produced in the
same gonad (syngonic type of reproduction). In another type, the egg
production by the gonad is preceded by the production of sperms by
the same gonad (protandry type of reproduction). Males, if present,
ia such cases are apparently functionless.
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Aberrent sex forms may be found in some
populations. Fully developed females may have rudimentary male
characters and vice versa. Such individuals are termed as
intersex. Female intersexes, in some cases, have been recorded to have
copulated with males and have produced eggs. Intersexes seem to result
from partial sex reversal under environmental influences.
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