Keywords Earthworm · Growth rate · Cocoon · Fecundity · Vermicomposting ·
Vermistablization
11.1 Introduction
Charles Darwin (1881) in his book The Formation of Vegetable Mould through the
Action of Worms mentioned earthworm’s role in the disappearance of overground
leaf litter. Since then, more than a century has passed to evaluate the role of
earthworms in the breakdown of organic wastes, plant litter, and their redistribution
and incorporation in the soils through their feeding, burrowing, and casting activities
(Lee 1985). Earthworm is physically an aerator, crusher, mixer, and chemically a
degrader and biologically a stimulator in the decomposer system (Mitchell 1978).
The burrowing activities of earthworm enhance aeration and porosity of the soil,
thereby improving its water-holding capacity.
Earthworms are metamerically segmented, vermiform, skin-breathing coelomate
invertebrates belonging to the class Oligochaeta under phylum Annelida. Their
locomotion is aided by the hydrostatic function of the coelome and segmentally
arranged chitinous setae. They possess a simple straight alimentary canal with
terminal mouth and anus. The circulatory system is of closed type. Central nervous
system is simple with paired cerebral ganglia (Brain), paired subesophageal ganglia,
circumesophageal connectives joining the cerebral with subesophageal ganglia and
ventral nerve cord that originates from subesophageal ganglia. They have no discrete
endocrine glands, instead the highly vascularized central nervous system along with
enormous number of neurosecretory cells act as the neuroendocrine system. The
neurosecretory cells are the sole source of hormones (neurohormone) in Oligochaetes that control all the physiological events such as growth, reproduction,
cocoon laying, regeneration, thermal acclimation, osmoregulation, etc.
Earthworms are found in the soils of forest, grassland, pasture, agricultural lands,
and also in the organic wastes. There are more than 8300 species of Oligochaeta of
which about 50% are terrestrial earthworms (Reynolds and Wetzel 2004). According
to Julka (2014), presently, 420 species of earthworms under 70 genera are found in
the Indian soil. Endemism, both at the genus and species level, is very high. About
71% of genera and 89% of species are endemic (Julka 2014).
Earthworm scientists often recognize three broad ecological groups of earthworms: epigeic, endogeic, and anecic. The epigeic earthworms (e.g. Perionyx
excavatus) inhabit degrading organic matter, such as cattle dung, litter heaps, etc.
They are generally small to medium-sized, deeply pigmented, flat ventrally, tolerant
to disturbance and have short life cycle, higher fecundity and regeneration capacity
(Bhattacharjee and Chaudhuri 2002; Banik and Chaudhuri 2017). Anecic earthworm
(Metaphire houlleti) lives in deep vertical burrows in the soil, and they emerge at
night to draw dead leaves and other organic decaying matter down into their
burrows. Anecics are phytogeophagous. They are generally large, moderate to
heavily pigmented and intolerant to disturbance. Endogeic species (Pontoscolex
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P. Chaudhuri and S. Debnath
Vermistablization
11.1 Introduction
Charles Darwin (1881) in his book The Formation of Vegetable Mould through the
Action of Worms mentioned earthworm’s role in the disappearance of overground
leaf litter. Since then, more than a century has passed to evaluate the role of
earthworms in the breakdown of organic wastes, plant litter, and their redistribution
and incorporation in the soils through their feeding, burrowing, and casting activities
(Lee 1985). Earthworm is physically an aerator, crusher, mixer, and chemically a
degrader and biologically a stimulator in the decomposer system (Mitchell 1978).
The burrowing activities of earthworm enhance aeration and porosity of the soil,
thereby improving its water-holding capacity.
Earthworms are metamerically segmented, vermiform, skin-breathing coelomate
invertebrates belonging to the class Oligochaeta under phylum Annelida. Their
locomotion is aided by the hydrostatic function of the coelome and segmentally
arranged chitinous setae. They possess a simple straight alimentary canal with
terminal mouth and anus. The circulatory system is of closed type. Central nervous
system is simple with paired cerebral ganglia (Brain), paired subesophageal ganglia,
circumesophageal connectives joining the cerebral with subesophageal ganglia and
ventral nerve cord that originates from subesophageal ganglia. They have no discrete
endocrine glands, instead the highly vascularized central nervous system along with
enormous number of neurosecretory cells act as the neuroendocrine system. The
neurosecretory cells are the sole source of hormones (neurohormone) in Oligochaetes that control all the physiological events such as growth, reproduction,
cocoon laying, regeneration, thermal acclimation, osmoregulation, etc.
Earthworms are found in the soils of forest, grassland, pasture, agricultural lands,
and also in the organic wastes. There are more than 8300 species of Oligochaeta of
which about 50% are terrestrial earthworms (Reynolds and Wetzel 2004). According
to Julka (2014), presently, 420 species of earthworms under 70 genera are found in
the Indian soil. Endemism, both at the genus and species level, is very high. About
71% of genera and 89% of species are endemic (Julka 2014).
Earthworm scientists often recognize three broad ecological groups of earthworms: epigeic, endogeic, and anecic. The epigeic earthworms (e.g. Perionyx
excavatus) inhabit degrading organic matter, such as cattle dung, litter heaps, etc.
They are generally small to medium-sized, deeply pigmented, flat ventrally, tolerant
to disturbance and have short life cycle, higher fecundity and regeneration capacity
(Bhattacharjee and Chaudhuri 2002; Banik and Chaudhuri 2017). Anecic earthworm
(Metaphire houlleti) lives in deep vertical burrows in the soil, and they emerge at
night to draw dead leaves and other organic decaying matter down into their
burrows. Anecics are phytogeophagous. They are generally large, moderate to
heavily pigmented and intolerant to disturbance. Endogeic species (Pontoscolex
180
P. Chaudhuri and S. Debnath