Indian Earthworm (Pheretima posthuma)ppt.pdf

Deals with brief description of Pheretima posthuma, useful for students appearing in different competitive exams, UG, PG, 10+2 , PreMed, PreVet, students. Prepared by Dr. Mohit Tiwari, Ex Principal, and Senior Faculty Biological Sciences with 46 years of teaching experience, recipient of 6 National and International awards author of 8 books and number of research papers. For more study contents you can visit my YouTube channel by Dr. Mohit Tiwari and my facebook page Understand Biological Sciences. To discuss or learn any topic you can call me on phone number 9839119223, 9839119920. No any fee is required .

2. 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.
•Coelomiccavity filled with coelomicfluid which act as
hydraulic endoskeleton which gives the tubular shape to the
body.

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

4. Morphology of Earthworm

5. Dorsal & Ventral view of Earthworm

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

7. Mouth of Earthworm

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

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

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

11. Function of different parts of gut -
•Prostomiumfor detection of taste and pH of food.
•Pharynx with chromophillcells secretes mucinand proteolyticenzymes.
•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 typhlosolarintestine –digestion of food.
•Intestinal caeca–secretes starch digesting enzymes.
•Typhlosolarregion of intestine for absorption of digested food.
•Typhlosole–Thick dorsal fold like villion 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 septalnephredia.

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

13. 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.

14. Blood vessels-
Dorsal blood vessel –1
st
to last segment, on dorsal surface of intestine, thick
walled, Blood flow Post -> Ant.
Ventral blood vessel -1
st
to last segment , on ventral side of intestine, blood
flow from Ant -> Post.
Supra oesophageal_ 8
th
-14
th
just above oesophagus
Lateral oesophagealfrom 1
st
to 14
th
, blood flow Ant -> Post. Placed on
ventrolateralside of gut.
Sub neural blood vessel –formed by fusion of lateral oesophagealblood vessel,
extends from 14
th
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 7
th
& 9
th
segment,
connects dorsal and ventral blood vessel.
2 pair lateral oesophagealhearts in 12
th
& 13
th
segments, connects supra
oesophagealand dorsal blood vessel with ventral blood vessel, contains 3 pair
of valves .
Anterior loops –2 pair, no valve, connects lateral oesophagealwith supra
oesophagealblood vessel.

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

16. Excretion –
Removal of metabolic waste by help of nephridia.
Earthworm is ureotelicanimal i.e. Urea is formed as main
excretory material.
Nephridiaare of 3 type-
A.Pharyngeal nephridia-in 4
th
, 5
th
, and 6
th
segment asmass
of cells, opens in pharyngeal chamber, Entronephric.
B.Integumentarynephridia-V shape, distributed all over
the skin except 1
st
& last segment, 200-250 /segment,
2000-2500 in 14
th
,15
th
&16
th
segment in region of
clitallumcalled nephridialgarden, Exonephric.
C.Septalnephridia-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 26
th
segment, through dorsal excretory canal , Entronephric.

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

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

19. Septalnephridia-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 26
th
segment, through dorsal excretory canal , Entronephric.

20. Septalnephridia

21. 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 14
th
segment
Male system -Testes 2 pair 9/10 & 10/11, testes sac 2
pair in 10 & 11, Seminal vesicle 11 & 12, vasaeffrentia2
pair from 10
th
& 11
th
to 18
th
segment, one pair prostate
gland between 17 to 20 segment, Male genital pore one
pair in 18
th
segment ventrolateralposition, male genital
papilla 2 pair ventrolateralin 17
th
& 19
th
segment.

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

24. Copulation and cocoon formation
Breeding/ copulation takes place in early morning of
rainy season. Earthworm is bisexual animal but
copulation and cross fertilzationtakes place, sperms of
earthworm are transferred in spermathecaeof each
other.
Ova are released in clitallumwhich slides in anterior
direction, while passing over spermathecaesperms are
released in clitallumwhere external fertilization takes
place. Clitallumis 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

25. 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