General discription of Pheretima posthuma, for Educational and competitive exams. Useful for NEET, NET, PGT, TGT, TET, SET, SSC, PG, UG, and other exams.

1. The Indian Earthworm
Part – 1
By- Dr. Mohit Tiwari

2. Basic description for 10+2 all boards,
different competitive exams and
NEET
By Dr. M.K.Tiwari

4. Classification –
Kingdom – Animalia
Phylum - Annelida
Class - Oligochaeta
Genus - Pheretima
Species - posthuma
•Body looks like made up of Rings (Annulus) so called annelida,
•True coelomate, Triploblastic,
•Body shows external as well as internal segmentation,
internally divided by partitions called septum.
• Body is tubular cylindrical with tubular intestine so called
tube within the tube organization.
•Coelomic cavity filled with coelomic fluid which act as
hydraulic endoskeleton which gives the tubular shape to the
body.

5. • Bilaterally symmetrical, Elongated, Tubular,
cylindrical body. Metameric segmentation.
• Deep brown or clay colored due pigment
porphyrin
• 15-20 cm x 3-5 mm in size, 100-120 segments in
body called metameres or somites

6. Morphology of Earthworm

7. Dorsal & Ventral view of Earthworm

8. General characters-
Mouth- Anterior terminal with Prostomium with Thigmo,
Thermo, Chemo sensitive receptors for sensitivity of Touch,
Temperature, Chemicals and pH. Prostomium is followed by 1st
segment of body called Peristomium surrounding mouth
opening.
Anus – Posterior terminal
Clitallum- Circular girdle like band on 14, 15 and 16th segment
of body well developed in breeding season.
Locomotion in earthworm takes place by help of S shaped
chitinious structure called Setae. Present in all segments of the
body except 1st and last segment.

9. Mouth of Earthworm

10. Dorsal view-
Dorsal side of body
shows a mid dorsal line
on body from 2nd to
last segment of body
due to dorsal blood
vessel.

11. Ventral view-
Ventral view of
earthworm shows
one female gonopore
on mid ventral side of
14th segment covered
with clitallum.
one pair male genital
pore on ventrolateral
side on 18th segment.
Two pair male genital
papilla on
ventrolateral side of
!7th & 19th segment of
body.

12. Digestive system-
•Tube with in tube organization.
•Alimentary canal from 1st to last segment of
body.
•Mouth – anterior terminal on 1st segment
surrounded by peristomium, prostomium in
front of mouth on dorsal side.
•Buccal cavity - 2nd segment.
•Pharynx- 3rd & 4th segment.
•Oesophagus - 5th to 8th segment
•Gizzard - 8th segment.
•Stomach – 9th to 14th
•Pre typhlosolar intestine – 14th to 26th
•Intestinal caeca - 26th - 22nd segment.
•Typhlosolar part of intestine – 26th – 80 / 100.
•Post typhlosolar intestine / Rectum – 80/100 to
last segment.
•Anus – posterior terminal end of last segment.

13. Function of different parts of gut -
•Prostomium for detection of taste and pH of food.
•Pharynx with chromophill cells secretes mucin and proteolytic enzymes.
•Esophagus – in some species secretes CaCO3 to neutralize acid in food.
•Gizzard for grinding of food.
•Stomach - secretes digestive enzymes for digestion of food.
•Pre typhlosolar intestine – digestion of food.
•Intestinal caeca – secretes starch digesting enzymes.
•Typhlosolar region of intestine for absorption of digested food.
•Typhlosole – Thick dorsal fold like villi on dorsal side of intestine to
increase surface area for absorption.
•Rectum – for storage of undigested food.
•Fecal matter of earthworm contains large quantity of nitrogenous
contents secreted by excretory structures septal nephredia.

14. Nervous system -
•Simple, from 3rd to last segment of
body.
•Supra pharyngeal ganglion one pair
on dorsal side of pharynx in 3rd
segment.
•Circum pharyngeal connective from
3rd to 4th around pharynx to connect
supra pharyngeal ganglion with sub
pharyngeal ganglion (Fused)on mid
ventral side of 4th segment.
•Ventral nerve cord from 4th to last
segment of body forming segmental
ganglion in each segment,
•Two pair nerves from each segmental
ganglion and one pair nerve from inter
segmental area.

15. Further studies -
1. Bhal Karm Narayan (1947), “The Zoological
memoirs Pheretima (The Indian Earthworm)”
Lucknow Publishing House, Lucknow
2. Tiwari Mohit Kumar (2021), “Bionomics,
Distribution, and Relationships of
Earthworms”.
Anusandhan, Part-9, Vol-1, P.P.- 46-50

16. The Indian Earthworm
Pheretima posthuma
Part – 2,
In Next video

17. The Indian Earthworm
Pheretima posthuma
Part – 2
By- Dr. Mohit Tiwari

18. Basic description for 10+2 all boards,
different competitive exams and
NEET
By- Dr. Mohit Tiwari

19. Circulatory system of Earthworm
Blood of earthworm is red in colure without RBC, Hemoglobin
(Erythrocruanine) is dissolved in plasma for oxygen transport.
Respiration through skin.

20. Blood vessels-
Dorsal blood vessel – 1st to last segment, on dorsal surface of intestine, thick
walled, Blood flow Post -> Ant.
Ventral blood vessel - 1st to last segment , on ventral side of intestine, blood
flow from Ant -> Post.
Supra oesophageal _ 8th -14th just above oesophagus
Lateral oesophageal from 1st to 14th , blood flow Ant -> Post. Placed on
ventrolateral side of gut.
Sub neural blood vessel – formed by fusion of lateral oesophageal blood vessel,
extends from 14th to last segment below ventral nerve cord, blood flow from
Ant-> Post
Hearts- 4 pairs
2 pair anterior lateral hearts , with 4 pairs of valves inside, in 7th & 9th segment,
connects dorsal and ventral blood vessel.
2 pair lateral oesophageal hearts in 12th & 13th segments, connects supra
oesophageal and dorsal blood vessel with ventral blood vessel, contains 3 pair
of valves .
Anterior loops – 2 pair, no valve, connects lateral oesophageal with supra
oesophageal blood vessel.

21. Hearts- 4 pairs
1.anterior lateral
hearts , with 4 pairs of
valves
2. lateral oesophageal
hearts , contains 3 pair
of valves .

22. Excretion –
Removal of metabolic waste by help of nephridia.
Earthworm is ureotelic animal i.e. Urea is formed as main
excretory material.
Nephridia are of 3 type-
A. Pharyngeal nephridia - in 4th, 5th, and 6th segment asmass
of cells, opens in pharyngeal chamber, Entronephric.
B. Integumentary nephridia - V shape, distributed all over
the skin except 1st & last segment, 200-250 /segment,
2000-2500 in 14th,15th &16th segment in region of
clitallum called nephridial garden, Exonephric.
C. Septal nephridia - Along with septum, from 15/16
segment to last segment , 40-50 in each row 80-100 per
segment, Twisted loop like , opens in intestine after 26th
segment, through dorsal excretory canal , Entronephric.

23. Pharyngeal nephridia - In 4th, 5th, and 6th segment
as mass of cells, opens in pharyngeal chamber, 6->3rd ,
5th->4th and 4th->4th segment, Entronephric.

24. Integumentary
nephridia –
V shape, distributed all
over the skin except 1st
& last segment, 200-250
/segment, 2000-2500 in
14th,15th &16th segment
in region of clitallum
called nephridial
garden, Exonephric.

25. Septal nephridia - Along with both side of septum,
from 15/16 segment to last segment , 40-50 in each row 80-100
per segment, Twisted loop like , opens in intestine after 26th
segment, through dorsal excretory canal , Entronephric.

26. Septal nephridia

27. Earthworm is a bisexual (Hermaphrodite).
Female system – Ovary one pair attached with 12/13
segment, Oviduct 1 pair from 13 to 14 segment, Female
genital opening single on mid ventral side of 14th segment
Male system - Testes 2 pair 9/10 & 10/11, testes sac 2
pair in 10 & 11, Seminal vesicle 11 & 12, vasaeffrentia 2
pair from 10th & 11th to 18th segment, one pair prostate
gland between 17 to 20 segment, Male genital pore one
pair in 18th segment ventrolateral position, male genital
papilla 2 pair ventrolateral in 17th & 19th segment.

28. Accessory reproductive structure -
Spermathecae – 4 pair in 6th,
7th, 8th and 9th, segment opens
at 5/6,6/7,7/8,8/9 segment on
ventrolateral side, bilobed sac
like structure for storage of
sperms during copulation.
Clitallum - a proteinaceous
girdle like structure on 14th,
15th and 16th segment ,forms
cocoon containing fertilized
eggs.

30. Copulation and cocoon formation
Breeding/ copulation takes place in early morning of
rainy season. Earthworm is bisexual animal but
copulation and cross fertilzation takes place, sperms of
earthworm are transferred in spermathecae of each
other.
Ova are released in clitallum which slides in anterior
direction, while passing over spermathecae sperms are
released in clitallum where external fertilization takes
place. Clitallum is released in soil as cocoon where
development of embryo takes place. In 8-10 weeks 1 or
2 young earthworms are formed in each cocoon.
Several cocoons are formed after single copulation

31. Habit, habitat and economic importance -
Found in moist soil up to depth of 35 -45 c.m.
Not found in very strong acidic or alkaline soil.
Active and breeds only in rainy season as this is a cold
blooded animal, in rest of the time lives in deep soil.
Feeds on soil (Detritus mode of feeding), utilizes organic
material present in soil.
Economically very important also called friend of farmers,
as they increase fertility of soil by adding nitrogen rich
fecal matter and also increase soil porosity or soil aeration.
END

32. Further studies -
1. Bhal Karm Narayan (1947), “The Zoological
memoirs Pheretima (The Indian Earthworm)”
Lucknow Publishing House, Lucknow
2. Tiwari Mohit Kumar (2021), “Bionomics,
Distribution, and Relationships of
Earthworms”.
Anusandhan, Part-9, Vol-1, P.P.- 46-50