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Epigeics species are useful for biosolid waste management as these worms can hasten the
composting process to a significant extent and produce better quality of vermicomposts,
compared with those prepared through traditional methods [25].
Two tropical species, African night crawler, Eudrilus eugeniae (Kinberg) (Figure 7a) and
Oriental earthworm, Perionyx excavates (Perrier) and two temperate ones, red earthworm,
Eisenia andrei (Bouche), tiger earthworm, Eisenia fetida (Savigny) (Figure 7b), and Lumbricus
rubellus are extensively used in vermicomposting [26, 27]. Most vermicomposting facilities
and studies are using the worms E. andrei and E. fetida due to their high rate of consumption,
digestion, and assimilation of organic matter, tolerance to a wide range of environmental
factors, short life cycles, high reproductive rates and endurance and resistance during handling
[28]. Eisenia fetida is used throughout the world for this purpose as it is ubiquitous, can tolerate
a wide range of temperature and can live in wastes with good moisture content [29, 30].
Eudrilus eugeniae and Perionyx excavatus is the other commonly used worm. Eudrilus
eugeniae is large in size, grows rapidly but has poor temperature tolerance, hence, may be
suitably used in the areas with less fluctuation of temperature (tropical areas).
Figure 7. Earthworms, a) Eudrilus eugeniae, b) Eisenia fetida
Earthworms grow best on easily metabolised organic matter and unassimilated carbohydrates,
which also support their reproduction. There was a positive correlation between the volatile
solids content of the waste and growth and reproduction. Earthworm growth slows down when
the C:N ratio and temperature are high. Biomass gain in E. fetida was found to depend on
population density and food type during vermicomposting [31, 32]. Scientific studies have
revealed that a single earthworm can gain biomass at a higher rate than those reared in groups.
Some studies reported a decrease in worm biomass in some cases in worms that were
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