Chapter 4 Earthworm

8/13/2019 Chapter 4 Earthworm

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FY.Bsc. Term I / Paper I Zoology

Chapter 4: Study of Earthworms

1) Earthworm appears brown due to the presence of pigment in its body

wa.

!) "eanin

B) #aemogobin

$) Porphyrin

%) Both &B) and &$)

!nswer is 'C

() hat wi happen if strong acoho are poured o*er the body of a i*e earthworm+

!) Bood oo,es through dorsa pore and utimatey due to oss of bood

earthworm wi die.

B) hite coeomic fuid oo,es out to neutrai,e the effect of acoho.

$) Earthworm wi become paraysed.

%) -othing wi happen.

1Sharps Notes

M M Multiple choice questions


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FY.Bsc. Term I / Paper I Zoology!nswer is 'B

) In Earthworm cocoons are found in

!) 10 1 and 12thsegment

B) 10 120 and 13thsegment

$) (0 (0 and (thsegment.

%) 0 0 and 2thsegment

!nswer is A

) Earthworm is paced in a group

!) 4igochaeta

B) Poychaeta

$) #irudinea

%) $rustacea

!nswer is A

) #ow many atera 4esophagea hearts are found in earthworm+

!) Two pairs0 one pair each in 1(thand 1thsegment.

B) Two pairs one pair each in 3thand 5thsegment.

$) Four pairs0 one pair each in 3th0 5th0 1(thand 1thsegment.

%) 6i7 pairs0 one pair each in 3th0 8th0 5th0 11th0 1(th0 and 1thsegment.

!nswer is B

2Sharps Notes


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FY.Bsc. Term I / Paper I Zoology2) Photoreceptors in earthworm occur in

!) Epidermis of 9entra body wa.

B) 6:in of Peristomium

$) 6:in of Prostomium

%) Epidermis of dorsa body wa.

!nswer is 'D

3) -ephridia of earthworm anaogues to

!) Trichocyst of Paramecium

B) Trachea of an insect

$) Fame ces of Taenia

%) ;is of fish.

!nswer is 'C

8) The bood *esses caed dorsa *esses of earthworm is

!) $oecting

B) %istributing

$) $oecting in first thirteen segments and distributing in the rest.

%) %istributing in first thirteen segments and coecting in rest.

!nswer is D) %orsa pores of earthworm are meant for passage of

!) $oeomic Fuid

B) Bood

$) aste materia

%) ;ametes

!nswer is A

11) In earthworm0 the function of choragogen ces is

!) E7cretion.

B) ?eproduction

$) %igestion

%) ?egeneration

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FY.Bsc. Term I / Paper I Zoology!nswer is A

1() Peptonephridia of earthworm are

!) E7onephric

B) Pharyngea nephridia

$) 6epta nephridia

%) Integumentary nephridia

!nswer is B

1) 6permathecae of earthworm ta:es part in

!) $oection of sperms of other animas

B) $oection of sperms of some animas

$) 6perm maturation

%) Fertii,ation

!nswer is A

1) The femae genita aperture in earthworm is present *entray on the segment.

!) 1>th

B) 1(th

$) 1th

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FY.Bsc. Term I / Paper I Zoology%) 18th

!nswer is 'C

1) In earthworm0 fertii,ation occurs in

!) 4*iduct

B) $iteum

$) 6permathecae

%) $ocoon

!nswer is D

12) $iteum of earthworm is connected with

!) Formation of $ocoon

B) $opuation

$) ?eease of sperms

%) 6torage of sperms

!nswer is 'A

13) The segmentation in an earthworm incudes interna seria repetition of

!) The intestine

B) "etanephridia

$) "usces

6Sharps Notes


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FY.Bsc. Term I / Paper I Zoology%) Both & B) and & $ )

!nswer is '% mm in ength and to mm in width.

Colouration:

Earthworm is of a gistening deepbrown in coour.

%orsa surface is dar:er than the *entra surface and carries a dar: cooured

median ine due to dorsa bood *esse which is seen through the integument.

Brown coour of worm is due to the pigment porphyrin present in body wa and

it protects the body against bright and utra*ioet radiation of sunight.

Se!mentation:

6oft and na:ed body of earthworm is di*ided into 1>> to 1(> simiar segments0

caed metameres or somites.

The body segmentation in earthworm is caed 'metameric segmentation

&metamerism).K

%ue to the presence of simiar body segments aong the ongitudina a7is of the

body.

The segments are without parapodia0 and segments are separated from each

other by distinct ringi:e groo*es.

E7terna segmentation corresponds with the interna segmentation of body.

1ead:

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The earthworm has no distinct head and no conspicuous sense organs on the

head.

The first segment at the anterior end of the body is caed 0uccal se!mentor

peristomiumbearing the termina crescentic mouth.

It is proonged anteriory into a feshyobe0 the prostomium which o*erhangs the

mouth.

1ind end:

The ast segment of the body is :nown as the ana segment and carries thetermina anus.

Clitellum:

In mature worms0 a conspicuous e7terna feature is a girdei:e thic: band of

ganduar tissue0 the clitellumor cin!ulum0 which competey surrounds

segments 1 to 18.

%ue to its presence0 the body is distinguished into precitear0 citear0 and

postcitear regions.

The segments forming citeum are not distinct.

$iteum is ganduar organ which secretes mucus0 abumen and an eggcase

or cocoon for eggs.

Setae:

!bout the midde of each segment there is a ring of tiny cur*ed bristes0 caed

setaeor chaetae0 formed of a horny nitrogenous organic substance0 :nown as

chitin.

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!bout 8> to 1(> setae are present on each segment.

Each seta is embedded in a sma pit in body wa0 caed setigerous or seta

sac.

It is formed by a singe formati*e ce present in the basa part of sac.

It has a faint yeow coour and is shaped i:e an eongated '6K with a swoen

midde part0 caed noduus.

!bout onethird of its ength proHects abo*e the surface of s:in in a contracted

segment.

The setae are operated by specia musces and hep the worm in ocomotion by

securing a firm grasp of the soi on surface of the ground.

They can be mo*ed in any direction and e7tended or withdrawn by the action of

these musces.

orn out setae fa out of the body wa and get renewed repeatedy.

There are no setae in the first and the ast segments and aso in the citeum of

a mature worm.

The arrangement of numerous setae in a ring in each segment is :nown as

perichaetine arrangement0 as found in Pheretima.

E5ternal Apertures:

The *arious apertures present on the body of earthworm are as foows A

Mouth:

The mouth is a crescentic aperture situated at the anterior end.

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It is surrounded by the first segment of the body &i.e.0 peristomium).

Anus :

The ast segment of the body or the ana segment bears the termina anus0

which is a *ertica siti:e aperture.

Dorsal pores:

"inute openings0 the dorsa pores0ie aong the middorsa ine.

one pore in each intersegmenta groo*e behind the 1(th segment0 e7cept the

ast.

By means of these pores the coeom communicates with the e7terior.

hen the worm is disturbed0 coeomic fuid may be eHected through these pores

for defense0 to increase the surface moisture or to moisten and ubricate the

was of the burrow.

>ephridiopores:

! arge number of *ery minute nephridiopores or the openings of the

integumentary nephridia are scattered a o*er the body e7cept the first two

segments.

Spermathecal pores:

The spermathecae open to the e7terior through four pairs of sma eiptica

apertures. the spermatheca pores 06ituated *entroateray in the inter

segmenta groo*es /20 2/30 3/8 and 8/5 segments.

Through these apertures spermato,oa are recei*ed from other worm during

copuation.

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It is nonceuar and finey striated0 iridescent0 doubeayered 0and is secreted

by underying epidermis.

It consists of coagenous protein and a poysaccharide aong with a itte

Guantity of geatin.

It bears many perforations0 through which open the epiderma mucous gands.

It protects the body from physica and chemica inHuries.

Epidermis:

It is singeayered and ying Hust beneath the cutice.

$es of epidermis are of *arious types performing different functions.

6upporting ces forming bu: of epidermis are of coumnar type. ;and ces in

cude numerous mucous ces and a few abumen ces pac:ed with secretory

granues.

Basa ces0 which are sma and rounded or conica 0 ie in spaces between

inner ends of supporting ces and gand ces .

?eceptor ces occur in groups with their outer ends gi*ing out fine hairi:e

processes.

Epidermis rests on a thin basement membrane.

Muscles:

"uscuature ies beow epidermis.

It consist of an outer thin ayer of circuar musce fibers running around the

body0 and an inner thic: ayer of ongitudina musce fibres running aong the

ength of body.

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@ongitudina musce fibers ie in parae bundes0 separated by connecti*e

tissue and strengthened by coagen fibers.

The musce fibers are unstriped0 ong and spinde shaped.

when the circuar musce fibers contract 0 the diameter of the body is narrowed

and the worm eongates

when the ongitudina musce fibers contract0 the diameter of the body becomes

greater and the worm shortens.

The two :inds of musce fibres are antagonistic0 because the contraction of onegoes with the rea7ation of the other.

Setal musculature:

Two additiona types of musce aso occur inserted at the base of each seta sac

bearing a seta.

These are a pair of protractor musces passing outwards to Hoin the circuar

musce ayer0 and a singe retractor musce0 passing inwards to Hoin another thin

sheet of circuar musces forming a ring beow the ongitudina musces.

! the musce fibres are unstriped.

Coelomic Epithelium:

The innermost ayer of the bodywa is the somatic peritoneum or the parieta

ayer of coeomic epitheium0 which aso forms the outer ining of the body

ca*ity.

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It consists of a singe ayer of fat pa*ement ces which are recogni,abe by

their nucei ony.

Coelom:

Body ca*ity of earthworm is a true coeom which ies between body wa and

aimentary cana .

It is ined by coeomic epitheium deri*ed from mesoderm.

It communicates with the e7terior through reproducti*e0 nephridia and dorsa

pores.

Morpholo!y of an earthworm

&'(#'Discuss the Di!esti,e system of earthworm

!nsA

%igesti*e 6ystemA

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FY.Bsc. Term I / Paper I ZoologyThe digesti*e system incudes the aimentary cana and the associated digesti*e

gands.

Alimentary canal:

!imentary cana is a compete and straight tube running aong the entire ength

of body.

"outh and anus constitute its anterior and posterior openings respecti*ey0 It is

functionay regionated into *arious parts which are bucca chamber0 pharyn70

oesophagus0 gi,,ard0 6tomach and intestine.

Buccal cham0er:

$rescentic mouth0 situated *entra to prostomium at the anterior end of

peristomium0 eads into a short and narrow protrusibe bucca chamber0

e7tending upto midde of third segment.

Its ining epitheium is thrown into ongitudina fods.

7haryn5:

Bucca chamber eads into a spacious pearshaped muscuar pharyn70 which

e7tends upto the fourth segment.

Its anterior end is mar:ed by the ner*e ring paced in a trans*erse groo*e

between it and bucca chamber.

Its ca*ity is somewhat dorso*entray compressed due to the presence of arge

ganduar pharyngea mass producing a sai*ary secretion.

@atera was of pharyn7 are pushed inside0 thus di*ide the pharyngea ca*ity

into a dorsa sai*ary chamber and a *entra conducting chamber.

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6ai*ary secretions contain mucus and proteoytic en,ymes which are poured

into the sai*ary chamber.

?esopha!us:

Behind pharyn7 ies the oesophagus or guet.

It is a short0 narrow0 thinwaed tube.

It e7tends up to the se*enth segment.

+i==ard:

4esophagus is modified into a prominent0 o*a0 hard and thic:waed muscuar

organ0 the gi,,ard0 ying in ninth segment.

Its muscuar wa consists of circuar musce fibres.

It is internay ined by a tough cutice.

Stomach:

;i,,ard is foowed by a short narrow tube0 the stomach0 which e7tends from

segments 5 to 10with a sphincter at each end.

Its was are highy *ascuar and ganduar and thrown into interna trans*erse

fods.


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Intestine is di*isibe into three parts A

(' 7retyphlosolar re!ion:

The anterior part of intestine ying between segments 1 to (2 is :nown as pre

typhosoar region.

From (2th segment are gi*en out e7ternay a pair of forwardydirected atera

conica outgrowths0 the intestinal caeca'

These are richy *ascuarand internay thrown into *iii:e processes.

#' @yphlosolar re!ionA

This region ies between (3th upto (( segments in front of anus.

This is characteri,ed by the presence of a highy ganduar and *ascuar

ongitudina ridge.

This is caed the typhosoe.

-' 7osttyphlosolar re!ion:

The ast part0 aso :nown as rectum0 and is of (( segments.

It opens outside through the termina anus.

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Di!esti,e of an earthworm

&'(-' Discuss the Circulatory system of an earthworm'

Ans:

Circulatory System:

$ircuatory or bood *ascuar system of earthworm is a cosed system consisting

of bood *esses and capiaries which ramify to a parts of the body.

Bood is composed of fuid pasma and coouress corpusces.

The red respiratory pigment0 haemogobin &or erythrocruorin) occurs disso*ed

in pasma.

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It gi*es a red coour to bood and aids in the transportation of o7ygen for

respiration'

Blood essels:

Bood *esses of Pheretima posthuma may be con*enienty grouped into three

types0 i.e.0 ongitudina0 atera and intestina pe7uses.

on!itudinal 0lood ,essels:

These are fi*e in number and run engthwise in the body.

(' Dorsal ,esselsA

It is the argest bood *esse of body running middorsay abo*e the aimentary

cana.

It has thic:0 muscuar and rhythmicay contractie wa and is pro*ided with a

pair of *a*es in front of the septum in each segment.

Bood fows through it from bac:ward to forward.

Behind 1th segment0 dorsa *esse is a coecting *esse0 recei*ing bood

through two pairs of commissura *esses from subneura *esse in each

segment.

In each of rd0 th0 th 02th and 8th segments0 a pair of stout pusating

branches send bood to the pharyngea nephiridia0 oesophagus and gi,,ard.

In front of 1th segment &anteriory)0 it distributes bood to the anterior regions of

aimentary cana and through the socaed hearts to *entra *esses.

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FY.Bsc. Term I / Paper I Zoology#' entrel ,essel:

It is a arge *esse0 runs mid*entray beow aimentary cana.

Its was are thin and noncontractie and *a*es are atogether absent.

Bood fows through it posteriory.

9entra *esse is principay a distributing *esse.

Besides in each segment behind 1th0 *entra *esse gi*es off a median *entro

intestina *esse to intestine.

-' ateral oesopha!eal ,essels:

These are two *esses ying one on either *entroatera side gut0 running from

the anterior end of body up to 1th segment.

These recei*e a pair of *entro tegumentary *esses in each segment.

Fowing posteriory0 some of its bood passes to the supraoesophagea *esse

?est of bood fows bac:ward into subneura *esse.

4' Su0neural ,essel:

It is a sender *esse which runs immediatey beneath the ner*e cord in mid

*entra position.

It e7tends from 1th segment upto the posterior end and is formed by the unionof two atera oesophagea *esses.

Fow of bood is from infront bac:wards.

It is a coecting *esse.

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It pours bood *ia a pair of commissuras in each segment0 into dorsa *esse.

/' Supra ?esopha!eal 0lood essel:

It is a short thinDwaed coecting *esse ying middorsay abo*e stomach and

confined to segments 5 to 1.

It is connected to atera oesophagea *esse through ( pairs of anterior oops

and to *entra *esse through two pairs of aterooesophagea hearts.

!t paces it di*ides into separate *esses which unite to form a singe *esse.

It coects bood from stomach0 gi,,ard and pumps it through atera

oesophagea hearts into *entra *esse.

ateral or trans,erse 0lood ,essels:

! the ongitudina bood *esses are interconnected with one another0 directy

or indirecty0 through numerous segmentay arranged trans*erse or atera

bood *esses.

@atera bood *esses of anterior region&first 1 segments) and those of

posterior region &behind 1 segment) of body are described separatey.

ateral Blood essels of Anterior 9e!ion

@atera Bood 9esses of !nterior ?egion

"irst (- se!ments%

(' 1eartsA

In each of the segments 30 50 1( and 1 is0 found a pair of arge0 thic:0 muscuar

and rhythmicay contractie *ertica *esses0 caed hearts.

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They pump bood from dorsa to *entra *esse0 whie fow in opposite direction is

pre*ented by interna *a*es.

#earts of 3th and 5th segments connect dorsa and *entra *esses ony0 are

caed atera hearts.

Those of 1(th and 1th segments connect both dorsa and supro oesophagea

*esses with *entra *esse0 are designated as aterooesophagea hearts.

#' Anterior loops:

There is a pair of thin waed 0nonDpusatie0 nonmuscuar and oopi:e broad*esses0 without *a*es 0 in each of the 1>th and 11th segments.

These *esses0 :nown as anterior oops0 carry bood from ateraoesophageas

into supraoesophagea *esse.

-' 9in! ,essels:

These are characteristic circuar *esses of stomach situated within its muscuar

coat0 about 1( *esses per segment.

Through these *esses0 bood or atera oesophageas reaches the supra

oesophagea.

4' entrote!umentary ,essels:

9entra *esse gi*es off a pair of *entro tegumentary *esses in each segment

to body wa0 septa0 nephridia and reproducti*e organs of the same segment.

ateral essels of


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FY.Bsc. Term I / Paper I Zoology(' Commissural ,essels:

There is a pair of these *esses in each segment.

They coect bood from body wa and each gi*es off a sma septointestina

branch to the intestine.

#' Dorso


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Interna pe7us passes on bood aong with absorbed nutrients0 to dorsa *esse

through dorsointestinas.

Blood +lands:

In segments 0 and 20 ying abo*e pharyngea mass and connected with

pharyngea of sai*ary gands0 are found sma0 redcooured0 foicuar bodies0

caed bood gands.

Each gand consists of a mass of oose ces surrounded by a capsue with a

syncytia wa.

Bood gands ser*e for the manufacture of bood corpusces and haemogobin.

Circulation of BloodA

Bood fows from behind to forward in dorsa *esse and from front to bac:wards

in *entra0 aterooesophagea0 supraoesophagea and subneura *esses.

9entra *esse is the main distributing *esse0 suppying bood to a parts of

body.

In first 1 segments0 it suppies bood to body wa0 septa0 nephridia and

reproducti*e organs through *entrotegumentaries.

Behind 1th segment0 it suppies bood to body wa and nephridia through

*entrotegumentaries and to gut wa through *entrointestinas.

6ubneura0 atera oesophageas and supraoesophageas are the main

coecting *esses.

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@atera oesophageas coect bood in first 1 segments from aimentary cana0

body wa0 nephridia0 septa and reproducti*e organs0 and discharge into supra

oesophagea through anterior oops and ring *esses.

6upraoesophagea aso coects bood from gi,,ard and stomach0 and pours it

into *entra *esse through aterooesophagea hearts.

6ubneura coects bood in the intestina region from *entra body wa and

sends into dorsa *esse through commissuras.

%orsa *esse functions both as a coecting and a distributing *esse.

In the intestina region0 it coects bood through dorsointestina from gut wa and

through commissuras from subneura *esse0 septa and nephridia.

In first 1 segments0 it distributes some bood through branches to aimentary

cana and pours the remaining bood through hearts into *entra *esse.

%igested food absorbed through the intestina wa is distributed to different parts

of body by the circuatory system.

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Circulatory system of an earthworm

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Circulation of 0lood in an earthworm

&'(4' Discuss the E5cretory system in earthworm'

Ans:

E5cretory or >ephridial System:

In Pheretima0 e7cretion is effected by segmentay arranged nephridia.

These are typicay unbranched and their inner ends open into coeom by aciiated funne0caed nephrostome.

6uch a nephridium0 opening by a ciiated funne0 is termed as metanephridium.

In Pheretima0 nephridia occur in a body segments e7cept the first three.

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!ccording to their ocation in body0 these are distinguished into typesD

Pharyngea0 Integumentary and 6epta.

7haryn!eal >ephridia:

These occur as paired tufts on side of pharyn7 and oesophagus in the th0 th

and 2th segments.

Each tuft consists of hundreds of coied branched tubues without nephrostomes.

In each tuft0 the termina ducts of a tubues Hoin to form a singe thic:waed

common duct.

Thus there are pairs of common pharyngea nephridia ducts0 which run

anteriory parae to the *entra ner*e cord.

%ucts of th and th segments open into pharyn70whie that of 2th segment open

into the bucca chamber.

Pharyngea nephridia are thus enteronephric.

ephridia:

These nephridia ie scattered on the entire inner or parieta surface of body wa

in each segment0 e7cept the first two.

There are (>>(> nephridia in each segment0but the segments of citeum

&segments 1 to 12)0 their number increases to more than (>>>.

Integumentary nephridia are 9shaped and ac: nephrostomes.

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Their termina ducts open on body surface independenty through minute

openings :nown as nephridiopores.

Integumentary nephridia are thus e7onephric.

Septal >ephridia:

These are the argest nephridia of Pheretima.

They are attached to both the faces of each inter segmenta septum behind

1th segment.

! typica septa nephridium consists of three main partsD-ephrostome0 body

and termina duct.

-ephrostome is a ciiated funne communicating with the coeom.

-ephrostome eads into the main body of nephridium through a short0 narrow

and ciiated tubeDi:e nec:.

Body consists of two parts0 a short straight obe and a ong twisted obe with a

narrow apica part.

The twisted obe consists of a pro7ima imb and a dista imb.

Pro7ima imb is Hoined to the nec:.

%ista imb of nephridium ends in termina duct.

Termina ducts open into a pair of septa e7cretory canas.

These canas discharge their contents into a pair of supraintestina e7cretory

ducts.

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E5cretory System in earthworm

&'(/' Discuss the 9eproducti,e system of Earthworm'

Ans:

9eproducti,e System:

Earthworms do not reproduce ase7uay.

The earthworms are monoecious &hermaphrodite) but they cannot fertii,e their

own eggs because they are protandrous.

!s a rue0 crossfertii,ation ta:es pace.

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It is preceded by copuation and cocoon formation.

Male 9eproducti,e ?r!ans:

These incude testes0 testis sacs0 semina *esices0 *asa deferentia0 prostate

gands and accessory gands.

@estes:

Two pairs of minute and obed testes are present0 one pair in 1>th and the other

pair in 11th segments.

They ie *enteroateray beneath the aimentary cana0 cose to mid*entra ine0

on either side of ner*e cord and attached to the anterior wa of their respecti*e

testis sacs.

Testes are we formed ony in young worms0 but become degenerated in

aduts.

@estis sac:

Both the testes of each segment are encosed within a wide0 thinwaed testis

sac.

Thus0 there are two testis sacs situated in segments 1> and 11.

Each testes sac encoses a pair of testes and a pair of ciiated spermiduca

funnes and aso communicates behind0 by a pair of tubuar connections with

two semina *esces of succeeding segment.

Testis sac of 11th segment is arge enough so as to encose aso the semina

*esices of that segment.

Seminal ,esicles:

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There are two pairs of arge0semina *esices ying in segments 11 and 1(

respecti*ey.

They are aso referred to as septa pouches since they grow as outgrowths of

the septa.

Testis sac of 1>thsegment communicates with semina *esices of 11thsegment

and testis sec of 11th segment with semina *esices of 1(th segment.

6emina *esices of 11thsegment ie encosed within testis sac of the same

segment0 whie those of 1(th segment ie free.

Spermiducal funnels:

There are two pairs of ciiated spermiduca funnes &or spermosettes)0 one of

them ying behind each testis in the same segment and encosed within the

same testis sac.

asa deferentia:

Each spermiduca funne eads behind into a sender0 ciiated0 threadi:e sperm

duct or *as deferens.

Two *asa deferentia of same side run cose together posteriory aong the *entra

body wa up to 18thsegment to Hoin the prostatic duct.

7rostate !land:

Prostate gands are a pair of fat 0soid0 irreguar and obuate masses0 ying one

on either side of gut and e7tending from 12th or 13th segment up to (>th or (1st

segment.

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Immediatey on emergence of prostatic duct from the inner side of gand0 it is

encosed in a common muscuar sheath0 aong with the two *asadeferentia on

its own side0 forming a common spermatic and prostatic duct0 within which the

three tubes remain separate.

Both common ducts cur*e inwards to open to the e7terior independenty by a

pair of mae genita pores *entray on 18th segment. Prostate gands

manufacture a fuid0 the prostatic fuid0 of un:nown function.

Accessory !lands:

In each of the 13th and 15 thsegments0 is found a pair of rounded white fuffy

masses0the accessory gands0 on *entroatera body wa0 one on either side of

ner*e cord.

They open to the e7terior by a number of ducts on two pairs of genita papiae0

situated e7ternay upon the 13th and 15th segments0 one on either side of mid

*entra ine.

Their secretion heps probaby in uniting the two worms during copuation.

From testes0 spermatogonia or spermmother ces are shed into testis sacs.

From here they enter semina *esices to undergo maturation and de*eop into

spermato,oa.

"ature sperms mo*e bac: into testis sac 0 enter spermiduca funnes0 tra*e

aong *ase deferentia and finay pass out through genita pores during

copuation.

emale 9eproducti,e ?r!ans:

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The femae reproducti*e organs consist of o*aries0 o*iduca funnes0 o*iducts

and spermathecae.

?,aries:

! pair of sma white digitate o*aries ies in 1th segment attached to the

posterior face of septum 1(/1 in form of it0 one on either side of *entra ner*e

cord.

Each o*ary is a white compact mass made of fingeri:e processes in which

o*a are arranged in a inear series in *arious stages of de*eopment.

?,iducal funnels:

! arge saucershaped o*iduca funne0 with much foded and ciiated margins0

ies immediatey behind each o*ary in the 1th segment.

?,iducts:

Each 4*iduca funne eads behind into a short conica ciiated tube0 the

o*iducts.

The two o*iducts run bac:wards0 perforate septum 1/1 and con*erge to meet

in *entra body wa beneath ner*e cord0 forming a *ery short common o*iduct.

It opens to the e7terior through the femae genita aperture0 situated mid

*entray on 1th segment.

Spermathecae:

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There are pairs of sma fas:shaped structures0 caed spermathecae or

receptacua seminais.

These are present *entroateray0 one pair in each of the segments 20 30 8 and

5.

Each spermatheca has a broad pearshaped body0 the ampua0 and a short

narrow nec:0 which gi*es off a narrow eongated bind caecum or di*erticuum

before opening to the e7terior.

Thus pairs of spermethecae open to outside by pairs of separate

spermatheca pores situated *enteroateray in the groo*es between /20 2/30

3/8 and 8/5 segments0 respecti*ey.

6permathecae recei*e sperms from another worm during copuation0 and store

them in their di*erticua in Pheretimaand in ampuae in other earthworms.

"ature o*a shed from o*aries are entanged by o*iduca funnes0 tra*e aong

o*iducts0 and pass out to the e7terior through the femae genita aperture0 to be

aid inside the cocoon.

Copulation and ertili=ation:

Earthworms are bise7ua0 sti seffertii,ation does not occur because they are

protandrous.

! reciproca crossfertii,ation of one worm are transferred to another during a

process0 termed copuation.

%uring copuation.two worms approach each other by their *entra surfaces with

head endo pointing in opposite directions0 so that the mae genita pores of each

ie against a pair of spermatheca pores of other.

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FY.Bsc. Term I / Paper I Zoologyertili=ation:

Fertii,ation occurs after the cocoon has been deposited in a moist pace.

$ocoon of Pheretima is a sma spherica body.

$ocoon formation ta:es pace in Pheretima time in summer0 especiay during

and after the monsoon.

"any cocoons may be formed in succession after each mating0 so that a

sperms stored in the spermathecae are not passed out at once.

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9eproducti,e system of earthworm'

&'(3' Discuss the >er,ous system of earthworm'

Ans:

>er,ous System

-er*ous system is we de*eoped and concentrated.

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It consists of three parts$entra0 Periphera and 6ympathetic ner*ous systems.

Central >er,ous System:

It comprises an anterior ner*e ring and a posterior *entra ner*e cord.

-er*e ring comprises paired cerebra gangia0 circumpharyngea connecti*es

and subpharyngea gangia.

! pair of cosey united white0 pearshaped cerebra or suprapharyngea

gangia0 forming the so caed brain0ie dorsay in the rd segment.

! pair of thic: stout circumor peripharyngea connecti*es arise from them

ateray and meeting *entray in a pair of fused subpharyngea gangia

beneath the pharyn7 in th segment.

In this way0 a compete ner*e ring is formed around pharyn7.

9entra ner*e cord arising from the subpharyngea gangia0 runs bac:wards in

mid*entra ine to the posterior end of body.

*entra ner*e cord appears to be singe but it is doube0 consisting of two

compacty united right and eft cords.

Each segmenta gangion aso represents the fusion of a pair of gangia0 one

beonging to each cord of the doube *entra ner*e cord.

#istoogicay0 the ner*e cord consists of ner*e fibres and ner*e ces.

E7ternay the ner*e cord is co*ered by a ayer of *iscera peritoneum0 beneath

which ies a thin ayer of ongitudina musce fibres0 surrounding a fibrous

capsue of epineurium.

Fibres form the core of the cord.55

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In the regions of segmenta gangia0 the two cores of ner*e fibres are

competey fused aong the midde ine.

4n the sides and beow cores of ner*e fibres ie the ner*e ces.

These are of two typesDmotor neurons and association neurons.

-er*e ces occur more in the gangia.

-er*e ces and ner*e fibres ie embeded in a mass of connecti*e tissue0 caed

neuro!lia.

7eripheral >er,ous System:

Each cerebra gangion gi*es off ateray 8 to 1> ner*es which inner*ate the

prostomium and bucca chamber.

-er*es from peripharyngea connecti*es suppy the peristomium and bucca

chamber0 whie ner*es from subpharyngea gangia suppy structures in the (0

and segments.

Each segmenta gangion of *entra ner*e cord gi*es off pairs of atera

ner*es0 one pair in front and two pairs behind the row of setae0 which inner*ate

the gut wa.0body wa and other interna organs of their segments.

-er*es are of mi7ed type0 consisting both afferent and sensory fibres and

efferent or motor fibres.

Sympathetic >er,ous System:

It consists of an e7tensi*e ner*e pe7us spread beneath epidermis0 within

musces of body wa and on aimentary cana.

These pe7us are connected with the peripharyngea connecti*es.

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Documents

Chapter 4 Earthworm