Earthworm:
Classification
Kingdom: animalia
Phylum: annelid
Class: oligochatea
Order: opisthopora
Genus: pheretima
Species: posthuma
morphology:
i) Shape and size: the body is long, symmetrical, cylindrical and narrow. The body is divided into numerous cross sections. The anterior end is tapering while posterior end is blunt. The dorsal surface is marked by the presence of dark median line of dorsal blood vessel which runs along the length of body. The ventral parts marked by genital openings and papillae
ii) Segmentation: the body consists of 100-120 segments. The segmentation is true i.e. external segmentation corresponds with internal segmentation. Hence, segmentation of earthworm is called metamerism.
ii) Peristomium: they have no distinct head, eyes and tentacles. The first segment of body is called peristomium. It bears crescent mouth.
iii) Clitellum: a girdle like thick band of glandular tissue is found toward the anterior end of body which is called as clitellum.clitellum extends from 14-16th segments. Glands of clitellum secrets mucus , albumin and cocoon for egg.
iv) Setae: they are the locomotary organelles of earthworm. They are found in all segment except first, last and cliteller region. All setae of a segment remain at the middle of the segment forming ring of setae. Each setae is a “s” shaped structure with swollen middle part called as nodule.1/3 part remains outside the body and is called as neck. 2/3 part remains inside the body called as base, setae is made up of nitrogenous compound chitin. The movement of setae is controlled by pair of protector and retractor muscles.
v) Openings of body: earthworms have several openings. They are:
a) Mouth: it is the anterior opening of alimentary canal and is present on ventral side of peristomium.
b) Anus: it is the posterior segment of alimentary canal and is present in the last segment.
c) Genital openings: it consists of two type of pore:-
1. Male genital pore: a pair of male genital pore is present ventro laterally in 18th segment. They are the opening of common spermatic and prostatic ducts.
2. Female genital pore: a single median female genital pore is present on the ventral surface of 14th segment. It is the opening of common oviducts.
d) Spermethecal openings: four pairs of Spermethecal openings are found in earthworm. They are the openings of spermethica.each pair of spermethecal openings is found in ventro-lateral position of intersegmental groove lying between 5/6,6/7,7/8,8/9th segments.
e) Nephridiopores: these are the openings of integumentary nephridia. Number of nephridiopores is found scattered on each segment except in first two segments.
f) Dorsal pores: there are some openings of coelomic chamber called as dorsal pores. A single median dorsal pore is found on dorsal surface of each intersegmental groove lying behind 12th segment except in last segment.
g) Genital papillae: there are two pairs of genital papillae found each in ventro-lateral position of 17th and 19th segment.
Digestive system:
The digestive system of earthworm consists of alimentary canal. Alimentary canal is the straight tube through the body length from mouth to anus.the parts of alimentary canal are:
Mouth: it is the anterior opening of alimentary canal and is present on ventral side of peristomium. It is crescentic opening. It opens into buccal chamber.
Buccal chamber: it is small, short, thin walled chamber. It extends upto the middle of third segment. Its wall are slightly folded and surrounded by muscular strands. Its outer wall remains supported by protractor and retractor muscles.
Pharynx: the buccal chamber open into pear shaped muscular pharynx. It extends upto 4th segment. It is separated from buccal chamber by a groove. Roof of pharynx is thick and glandular and acts as pharyngeal mass which is lined by ciliated epithelium. It contains connective tissue, blood vessel and salivary gland. Pharynx is divided into salivary chamber and conducting chamber. Mucus and proteolytic enzyme are produced here.
Oesophagus: pharynx opens into short, narrow, thin walled tube, the oesophagus. It passes food from pharynx to gizzard. It extend from 4-8th segment.
Gizzard: the oesophagus leads into a prominent, oval, thick walled, hard, highly muscular organ gizzard. The muscular wall consists of circular muscles fiber surrounded by tough cuticle. It is found on 8th segment and ground the food into fine state.
Stomach: the stomach is the short, narrow, highly vascular region of the gut. It extends from 9th – 14th segment. Each end of stomach is spintchered.it is rich in glandular cell and is folded inside. The gland secrets proteolytic enzyme and it digests the protein. It also contains calciferous gland to secrete calcium carbonate to neutralize the food. Calciferous glands are also excretory in function.
Intestine: stomach is followed by a long, wide and thin walled chamber called as intestine. It extends from 15th segment to the last segment. It is folded internally and is ciliated and glandular. These folding are called villi.one of these villi is larger and called as typhlosole.typlosole runs from 26th segment to last 23,25th segment. Villi absorb the nutrition. It divides intestine into:-
Pre-typhlosoler region: it extends from 15th to 26th segment. It is folded internally with absence of typhlosole. At 26th segment, it contains two outgrowths, the intestinal caecum. The caecum runs forward upto 22th segment. It secrets amylatic enzyme to digest starch.
Typhlosoler region: it is 2nd part of stomach. It extends from 26th segment to last 23,25th segments. It contains typhlosole, which increase area of absorption.
Post-typhlosoler: it is also called rectum. It extends from last 23,25th segment to last segment. It is the last part of intestine. It contains no villi.
Anus: the last segment of earthworm is called anus.the passes out undigested food, wastes and mud.
Food and feeding:-
The earth worm feed on decaying organic matter. The proportion of organic matter is less in soil so they ingest a large amount of soil. They also feed directly on leaves, grass, protozoan, nematodes, insects and others. The food is ingested by pumping action of pharynx. Pumping action is bought by muscles fibres.it draws food into buccal chamber by pressing mouth and sucking.
Digestive glands:- the mucus secreting glands present all over the alimentary canal secrets mucus to keep the gut sleepery.the salivary gland, the calciferous gland, the intestinal glands,caeca etc are the various digestive glands of earthworm. They produce enzyme to digest food.
Physiology:- the swallowed food passes into the pharynx through buccal chamber. In pharynx, digestive enzymes mucin and proteolytic enzyme is secreted and poured into food. Mucin lubricates the food and proteolytic enzyme digest protein. In gizzard food particles are pulverized into fine state. The food now passes into stomach and mix with secretion of calciferous gland which neutralize the food. When the food is passed into intestine, it mixes with pepsin, tripsin, amylase, lipase and cellulase. Now pepsin converts protein into peptones and proteases. Trypsin hydrolyses peptones to amino acids. Amylase converts starch into sugar. Lipase hydrolyses fats into glycerol and fatty acid. Cellulose digests cellulose into cellulobiose.
Absorption:- the digested food is absorbed by intestinal villi and typhlosole. Active digestion takes place at typhlosoler region. Absorbed food is passed into blood vessel by capillary network. Finally it reaches at coelomic chamber and coelomic food transport it all over the body.
Ejection:- all the undigested food and mud are passed out from the body through anus in the form of worm castings.
Nervous system:-
Nervous system in earthworm is well developed. It consists of:-
Central nervous system
Peripheral nervous system
Systemic nervous system
Central nervous system
it consists of nerve ring and ventral nerve cord. The nerve ring consists of supra pharyngeal ganglia, circumpharengeal connectives and sub pharyngeal ganglia.
A pair of supra pharyngeal ganglia are present on the dorsal surface of depression lying between buccal chamber and pharynx at the middle of 3rd segment. Each ganglia is small, rounded and white colored structure. The two ganglia remains fused with each other. They are called as cerebral ganglia or brain.
The circum pharyngeal connectives arises from the outer side of each supra pharyngeal ganglia and run posterior-ventrally encircling the pharynx and meet with the subpharengeal ganglia.
A pair of subpharengeal ganglia is present ventrally below the pharynx in 4th segment. They remain fused with each other at middle.
Due to the position of suprapharyngeal ganglia, circum pharyngeal connectives and sub pharyngeal ganglia, a ring like structure is formed around pharynx and is called nerve ring.
The ventral nerve cord arises from the sub pharyngeal ganglia and runs mid-ventrally upto the posterior end of the body. From 5th segment, at the middle of each segment, the ventral nerve cord remains enlarged to form segmental ganglia .though it seems single from outside, ventral nerve cord consist of two nerve cords each arising from each subpharengeal ganglia.
Histologically, ventral nerve cord consists of nerve cells and nerve fibres.the fibers are present at the centre forming the core. The nerve cells are present on the side and under surface of core of fibers. Dorsal to the core of fibres, 4-giant nerve fibers are present which help in rapid conduction of nerve impulse. All these remains in mass of connective tissue called as neuralgia which remain in capsular form and covered by epineurium.nerve cord is externally covered by longitudinal muscle and peritoneum.
Peripheral nervous system
the nerves arising from central nervous system form peripheral nervous system, about 8-10 pairs of nerves arises from the supra pharyngeal ganglia and these nerves pass into prostomium,buccal chamber and pharynx. Two pair of nerves arises from circum pharyngeal connectives and each pair pass into buccal chamber and peristomium. Three pair of nerves arises from sub pharyngeal ganglia and each pair pass into 2nd, 3rd and 4th segment. Three pair of nerves arises from each segmental ganglia and these pass into different organ of segment. The nerves are both sensory and motor in nature.
Systemic nervous system
it consists of network of nerve fibers i.e. nerve plexus lying on muscles if body wall and muscles of wall of alimentary canal. It remains connected with the circumpharengeal connectives.
Excretory system:-
It involves the process of removal of nitrogenous metabolic wastes from body. Nephridia are the excretory organelles of earthworm. Each nephridia is coiled, tubular structure and is highly vascular.nephridium consists of three part i.e. nephrostome, mainbody and terminal duct. In some cases nephrostome may be lost. If terminal duct of nephridia opens inside body,it is called entero nephric and if terminal duct of nephridia opens outside body,it is called exonephric. Types of nephridia are:-
Septal nephridia
Pharyngeal nephridia
Integumentary nephridia
Septal nephridia:- Septal nephridia are present on the surface of septum. They are present on both surface of lying between 14th to last segment. On each surface of septum, two rows of nephridia are present and each row contains about 20-25 nephridia. Thus 80-100 nephridia are found on each segment. Each Septal nephridium is contained of nephrostome, mainbody and terminal duct. The nephrostome is ciliated funnel shaped body and it opens into coelom. Its mouth remains guarded by upper and lower lips. The upper lip consists of large central cell and 8-9 marginal cells. The lower lip contains 4-5 compact cells.
The nephrostome remains connected with main body by a short neck. The main body consists of straight lobe and twisted lobe. The length of st-lobe is half of twisted lobe. The twisted lobe consist twisted proximal and distal limb and a short apical part.
Pharyngeal and Integumentary nephridia : these Nephridia regulate the volume and composition
of the body fluids. A nephridium starts out as a
funnel that collects excess fluid from coelomic
chamber. The funnel connects with a tubular part
of the nephridium which delivers the wastes
through a pore to the surface in the body wall into the digestive tube.
Reproductive system :
Earthworm is hermaphrodite , i.e.,testes and ovaries are present in the same
individual .
There are two pairs of
testes present in the 10th and 11th segments.
Their vasa deferentia run up to the 18th segment
where they join the prostatic duct. Two pairs of
accessory glands are present one pair each in
the 17th and 19th segments. The common prostate
and spermatic duct i.e vasa differentia opens to
the exterior by a pair of male genital pores on
the ventro lateral side of the 18th segment. Four
pairs of spermathecae are located in 6th-9th
segments .single pair lie in each segment. They receive
and store spermatozoa during copulation. One
pair of ovaries is attached at the inter-segmental
septum of the 12th and 13th segments. Ovarian
funnels are present below the ovaries which
continue into oviducts and they join together and open on
ventral side as a single median female genital
pore on the 14th segment.
A mutual exchange of sperm soccurs between
two earth worms during mating. One earthworm has to find
another worm and they mate juxtaposing
opposite gonadial openings exchanging packets
of sperm called spermatophore. Mature sperm
and egg cells and nutritive fluid are deposited in
cocoons produced by the gland cells of clitellum.
Fertilisation and development occur within the
cocoons which are deposited in soil. The ova
are fertilised by the sperm cells within the
cocoon which then slips off the worm and is
deposited in or on the soil. The cocoon holds the
worm embryos. After about 3 weeks, each cocoon
produces two to twenty baby worms with an
average of four. Earthworms development is
direct, i.e., there is no larva formed.
The importance of earthworms in agriculture
1. Their burrows increase soil drainage.
2. Their burrows increase soil aeration.
3. They soften the soil allowing easier root penetration.
4. They speed up the formation of humus.
5. They mix soil layers.
6. Increase the depth of topsoil by bringing subsoil to the surface.
7. The passage of soil through their alimentary canal results in the particles of soil being ground to a finer texture in the gizzard of the worm.
8. Their dead bodies become part of humus.
9. They reduce the acidity of the soil.
Classification
Kingdom: animalia
Phylum: annelid
Class: oligochatea
Order: opisthopora
Genus: pheretima
Species: posthuma
morphology:
i) Shape and size: the body is long, symmetrical, cylindrical and narrow. The body is divided into numerous cross sections. The anterior end is tapering while posterior end is blunt. The dorsal surface is marked by the presence of dark median line of dorsal blood vessel which runs along the length of body. The ventral parts marked by genital openings and papillae
ii) Segmentation: the body consists of 100-120 segments. The segmentation is true i.e. external segmentation corresponds with internal segmentation. Hence, segmentation of earthworm is called metamerism.
ii) Peristomium: they have no distinct head, eyes and tentacles. The first segment of body is called peristomium. It bears crescent mouth.
iii) Clitellum: a girdle like thick band of glandular tissue is found toward the anterior end of body which is called as clitellum.clitellum extends from 14-16th segments. Glands of clitellum secrets mucus , albumin and cocoon for egg.
iv) Setae: they are the locomotary organelles of earthworm. They are found in all segment except first, last and cliteller region. All setae of a segment remain at the middle of the segment forming ring of setae. Each setae is a “s” shaped structure with swollen middle part called as nodule.1/3 part remains outside the body and is called as neck. 2/3 part remains inside the body called as base, setae is made up of nitrogenous compound chitin. The movement of setae is controlled by pair of protector and retractor muscles.
v) Openings of body: earthworms have several openings. They are:
a) Mouth: it is the anterior opening of alimentary canal and is present on ventral side of peristomium.
b) Anus: it is the posterior segment of alimentary canal and is present in the last segment.
c) Genital openings: it consists of two type of pore:-
1. Male genital pore: a pair of male genital pore is present ventro laterally in 18th segment. They are the opening of common spermatic and prostatic ducts.
2. Female genital pore: a single median female genital pore is present on the ventral surface of 14th segment. It is the opening of common oviducts.
d) Spermethecal openings: four pairs of Spermethecal openings are found in earthworm. They are the openings of spermethica.each pair of spermethecal openings is found in ventro-lateral position of intersegmental groove lying between 5/6,6/7,7/8,8/9th segments.
e) Nephridiopores: these are the openings of integumentary nephridia. Number of nephridiopores is found scattered on each segment except in first two segments.
f) Dorsal pores: there are some openings of coelomic chamber called as dorsal pores. A single median dorsal pore is found on dorsal surface of each intersegmental groove lying behind 12th segment except in last segment.
g) Genital papillae: there are two pairs of genital papillae found each in ventro-lateral position of 17th and 19th segment.
Digestive system:
The digestive system of earthworm consists of alimentary canal. Alimentary canal is the straight tube through the body length from mouth to anus.the parts of alimentary canal are:
Mouth: it is the anterior opening of alimentary canal and is present on ventral side of peristomium. It is crescentic opening. It opens into buccal chamber.
Buccal chamber: it is small, short, thin walled chamber. It extends upto the middle of third segment. Its wall are slightly folded and surrounded by muscular strands. Its outer wall remains supported by protractor and retractor muscles.
Pharynx: the buccal chamber open into pear shaped muscular pharynx. It extends upto 4th segment. It is separated from buccal chamber by a groove. Roof of pharynx is thick and glandular and acts as pharyngeal mass which is lined by ciliated epithelium. It contains connective tissue, blood vessel and salivary gland. Pharynx is divided into salivary chamber and conducting chamber. Mucus and proteolytic enzyme are produced here.
Oesophagus: pharynx opens into short, narrow, thin walled tube, the oesophagus. It passes food from pharynx to gizzard. It extend from 4-8th segment.
Gizzard: the oesophagus leads into a prominent, oval, thick walled, hard, highly muscular organ gizzard. The muscular wall consists of circular muscles fiber surrounded by tough cuticle. It is found on 8th segment and ground the food into fine state.
Stomach: the stomach is the short, narrow, highly vascular region of the gut. It extends from 9th – 14th segment. Each end of stomach is spintchered.it is rich in glandular cell and is folded inside. The gland secrets proteolytic enzyme and it digests the protein. It also contains calciferous gland to secrete calcium carbonate to neutralize the food. Calciferous glands are also excretory in function.
Intestine: stomach is followed by a long, wide and thin walled chamber called as intestine. It extends from 15th segment to the last segment. It is folded internally and is ciliated and glandular. These folding are called villi.one of these villi is larger and called as typhlosole.typlosole runs from 26th segment to last 23,25th segment. Villi absorb the nutrition. It divides intestine into:-
Pre-typhlosoler region: it extends from 15th to 26th segment. It is folded internally with absence of typhlosole. At 26th segment, it contains two outgrowths, the intestinal caecum. The caecum runs forward upto 22th segment. It secrets amylatic enzyme to digest starch.
Typhlosoler region: it is 2nd part of stomach. It extends from 26th segment to last 23,25th segments. It contains typhlosole, which increase area of absorption.
Post-typhlosoler: it is also called rectum. It extends from last 23,25th segment to last segment. It is the last part of intestine. It contains no villi.
Anus: the last segment of earthworm is called anus.the passes out undigested food, wastes and mud.
Food and feeding:-
The earth worm feed on decaying organic matter. The proportion of organic matter is less in soil so they ingest a large amount of soil. They also feed directly on leaves, grass, protozoan, nematodes, insects and others. The food is ingested by pumping action of pharynx. Pumping action is bought by muscles fibres.it draws food into buccal chamber by pressing mouth and sucking.
Digestive glands:- the mucus secreting glands present all over the alimentary canal secrets mucus to keep the gut sleepery.the salivary gland, the calciferous gland, the intestinal glands,caeca etc are the various digestive glands of earthworm. They produce enzyme to digest food.
Physiology:- the swallowed food passes into the pharynx through buccal chamber. In pharynx, digestive enzymes mucin and proteolytic enzyme is secreted and poured into food. Mucin lubricates the food and proteolytic enzyme digest protein. In gizzard food particles are pulverized into fine state. The food now passes into stomach and mix with secretion of calciferous gland which neutralize the food. When the food is passed into intestine, it mixes with pepsin, tripsin, amylase, lipase and cellulase. Now pepsin converts protein into peptones and proteases. Trypsin hydrolyses peptones to amino acids. Amylase converts starch into sugar. Lipase hydrolyses fats into glycerol and fatty acid. Cellulose digests cellulose into cellulobiose.
Absorption:- the digested food is absorbed by intestinal villi and typhlosole. Active digestion takes place at typhlosoler region. Absorbed food is passed into blood vessel by capillary network. Finally it reaches at coelomic chamber and coelomic food transport it all over the body.
Ejection:- all the undigested food and mud are passed out from the body through anus in the form of worm castings.
Nervous system:-
Nervous system in earthworm is well developed. It consists of:-
Central nervous system
Peripheral nervous system
Systemic nervous system
Central nervous system
it consists of nerve ring and ventral nerve cord. The nerve ring consists of supra pharyngeal ganglia, circumpharengeal connectives and sub pharyngeal ganglia.
A pair of supra pharyngeal ganglia are present on the dorsal surface of depression lying between buccal chamber and pharynx at the middle of 3rd segment. Each ganglia is small, rounded and white colored structure. The two ganglia remains fused with each other. They are called as cerebral ganglia or brain.
The circum pharyngeal connectives arises from the outer side of each supra pharyngeal ganglia and run posterior-ventrally encircling the pharynx and meet with the subpharengeal ganglia.
A pair of subpharengeal ganglia is present ventrally below the pharynx in 4th segment. They remain fused with each other at middle.
Due to the position of suprapharyngeal ganglia, circum pharyngeal connectives and sub pharyngeal ganglia, a ring like structure is formed around pharynx and is called nerve ring.
The ventral nerve cord arises from the sub pharyngeal ganglia and runs mid-ventrally upto the posterior end of the body. From 5th segment, at the middle of each segment, the ventral nerve cord remains enlarged to form segmental ganglia .though it seems single from outside, ventral nerve cord consist of two nerve cords each arising from each subpharengeal ganglia.
Histologically, ventral nerve cord consists of nerve cells and nerve fibres.the fibers are present at the centre forming the core. The nerve cells are present on the side and under surface of core of fibers. Dorsal to the core of fibres, 4-giant nerve fibers are present which help in rapid conduction of nerve impulse. All these remains in mass of connective tissue called as neuralgia which remain in capsular form and covered by epineurium.nerve cord is externally covered by longitudinal muscle and peritoneum.
Peripheral nervous system
the nerves arising from central nervous system form peripheral nervous system, about 8-10 pairs of nerves arises from the supra pharyngeal ganglia and these nerves pass into prostomium,buccal chamber and pharynx. Two pair of nerves arises from circum pharyngeal connectives and each pair pass into buccal chamber and peristomium. Three pair of nerves arises from sub pharyngeal ganglia and each pair pass into 2nd, 3rd and 4th segment. Three pair of nerves arises from each segmental ganglia and these pass into different organ of segment. The nerves are both sensory and motor in nature.
Systemic nervous system
it consists of network of nerve fibers i.e. nerve plexus lying on muscles if body wall and muscles of wall of alimentary canal. It remains connected with the circumpharengeal connectives.
Excretory system:-
It involves the process of removal of nitrogenous metabolic wastes from body. Nephridia are the excretory organelles of earthworm. Each nephridia is coiled, tubular structure and is highly vascular.nephridium consists of three part i.e. nephrostome, mainbody and terminal duct. In some cases nephrostome may be lost. If terminal duct of nephridia opens inside body,it is called entero nephric and if terminal duct of nephridia opens outside body,it is called exonephric. Types of nephridia are:-
Septal nephridia
Pharyngeal nephridia
Integumentary nephridia
Septal nephridia:- Septal nephridia are present on the surface of septum. They are present on both surface of lying between 14th to last segment. On each surface of septum, two rows of nephridia are present and each row contains about 20-25 nephridia. Thus 80-100 nephridia are found on each segment. Each Septal nephridium is contained of nephrostome, mainbody and terminal duct. The nephrostome is ciliated funnel shaped body and it opens into coelom. Its mouth remains guarded by upper and lower lips. The upper lip consists of large central cell and 8-9 marginal cells. The lower lip contains 4-5 compact cells.
The nephrostome remains connected with main body by a short neck. The main body consists of straight lobe and twisted lobe. The length of st-lobe is half of twisted lobe. The twisted lobe consist twisted proximal and distal limb and a short apical part.
Pharyngeal and Integumentary nephridia : these Nephridia regulate the volume and composition
of the body fluids. A nephridium starts out as a
funnel that collects excess fluid from coelomic
chamber. The funnel connects with a tubular part
of the nephridium which delivers the wastes
through a pore to the surface in the body wall into the digestive tube.
Reproductive system :
Earthworm is hermaphrodite , i.e.,testes and ovaries are present in the same
individual .
There are two pairs of
testes present in the 10th and 11th segments.
Their vasa deferentia run up to the 18th segment
where they join the prostatic duct. Two pairs of
accessory glands are present one pair each in
the 17th and 19th segments. The common prostate
and spermatic duct i.e vasa differentia opens to
the exterior by a pair of male genital pores on
the ventro lateral side of the 18th segment. Four
pairs of spermathecae are located in 6th-9th
segments .single pair lie in each segment. They receive
and store spermatozoa during copulation. One
pair of ovaries is attached at the inter-segmental
septum of the 12th and 13th segments. Ovarian
funnels are present below the ovaries which
continue into oviducts and they join together and open on
ventral side as a single median female genital
pore on the 14th segment.
A mutual exchange of sperm soccurs between
two earth worms during mating. One earthworm has to find
another worm and they mate juxtaposing
opposite gonadial openings exchanging packets
of sperm called spermatophore. Mature sperm
and egg cells and nutritive fluid are deposited in
cocoons produced by the gland cells of clitellum.
Fertilisation and development occur within the
cocoons which are deposited in soil. The ova
are fertilised by the sperm cells within the
cocoon which then slips off the worm and is
deposited in or on the soil. The cocoon holds the
worm embryos. After about 3 weeks, each cocoon
produces two to twenty baby worms with an
average of four. Earthworms development is
direct, i.e., there is no larva formed.
The importance of earthworms in agriculture
1. Their burrows increase soil drainage.
2. Their burrows increase soil aeration.
3. They soften the soil allowing easier root penetration.
4. They speed up the formation of humus.
5. They mix soil layers.
6. Increase the depth of topsoil by bringing subsoil to the surface.
7. The passage of soil through their alimentary canal results in the particles of soil being ground to a finer texture in the gizzard of the worm.
8. Their dead bodies become part of humus.
9. They reduce the acidity of the soil.
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