- Describe the circulatory system of Periplaneta.
- Haemocoel:-
- Pericardial sinus (surrounding the heart & aorta).
- Perivisceral sinus (surrounding the various visceral organs)
- Perineural sinus ( surrounding the ventral nerve cord).
- Heart:-
- Position:- the heart is present along the middorsal line of the body. It extends from the tip of the head up to the abdominal end.
- Attachment:- The heart remains attached with the dorsal body wall dorsally & the dorsal diaphragm ventrally by a sets of alary muscles. The alary muscles hold the heart in position.
- Structure:- The heart of cockroach is an elongated muscular tube. It consists of 13 segmentally arranged funnel shaped chambers.
- Haemolymph:-
- Course of circulation:-
- Mechanism:-
- Functions:-
- Acts as the reservoir of water.
- Transports food materials, hormones, excretory products etc.
- Maintains the hydrostatic pressure of the body.
- Performs blood coagulation & wound healing.
- Describe the male reproductive system of Periplaneta sp.
- Peripheral long tubules or utriculi majors.
- Central short tubules called utriculi breviores.
- Behind the short central tubules are some short but more bulbous, opaque white tubules, forming seminal vesicles.
- Describe briefly the female reproductive system of Periplaneta sp.
- Terminal filament:- Anterior most, tapering thread like continuation of the connective tissue layer. It serves to suspend the ovariole in the haemocoel.
- Germarium:-The anterior 1/3 part is the germarium containing only the primordial germ cells & oogonia.
- Vitellarium:- It is the posterior part containing ova in various stages of development & maturation. The wall of ovariole encloses each ovum in a follicle. These follicles gives a beaded appearance to ovariole.
- Egg chamber:- The vitellarium opens posteriorly into a small, thick, oval egg chamber. It contains a single, large, mature ovum at a time.
- Stalk or pedicel:- The egg chamber continues posteriorly into thin walled, hollow stalk or pedicel. It opens into the lateral oviduct.
- Give an account of the digestive system in Periplaneta sp.
- Alimentary canal:-
- Foregut:-
- Mouth:-
- Mouth cavity;-
- Pharynx:-
- Oesophagus:-
- Crop:-
- Gizzard:-
- ) Armarium:-
- ) Stomodaeal valve:-
- Midgut:-
- Hepatic caeca:-
- Malpighian tubules:-
- Hindgut:-
- Ileum:-
- Colon:-
- Rectum:-
- Digestive glands:-
- Describe the respiratory organs & mechanism of respiration in Periplaneta sp.
- Spiracle/ Stigmata:-
- Tracheae:-
- Tracheoles:-
- Name the major endocrine glands of Periplaneta sp.
- Secretion of utriculi majors form the inner layer of spermatophore.
- Secretion of utriculi breviores nourishes the sperms.
- Seminal vesicles are meant for storage of sperm.
The circulatory
system of Periplaneta is of open type
as the blood or haemolymph flows freely within the body cavity or haemocoel.
There is a heart & aorta but no capillaries & veins.
Circulatory system
consists of haemocoel, heart & haemolymph.
Body cavity of
cockroach is known as haemocoel as it remains filled with haemolymph (blood).
The coelom is
divided into 3 main sinuses by a dorsal & ventral horizontal diaphragm:-
In between the 2
chambers a pair of ostia are present.
The haemolymph or
blood of cockroach consists of clear colourless plasma & haemocytes. The
haemocytes remain suspended into the plasma.
The haemocytes are
of 3 types - prohaemocytes, transitional haemocytes & large haemocytes.
According to
Jones, haemocytes may be classified into 2 broad categories- plasmocytes &
coagulocytes.
Course of blood flow may be summarized as follows-
Heart (via anterior
aorta) to sinuses of head region to perineural
sinus (via ventral diaphragm) to perivisceral
sinus (via dorsal diaphragm) to pericardial
sinus (via ostia) to heart.
The circulation of
the blood is controlled by the contraction & relaxation of the alary
muscles. In fact the alary muscles control the opening & closer of ostia.
As the blood lack
respiratory pigments it doesn’t carry respiratory gases. Rather it
Male reproductive
system of Periplaneta includes a pair of testis, vasa differentia, an ejaculatory duct, mushroom gland, phallic
gland, genital pouch & external
genitalia.
Testis:-
Male gonads are a
pair of testis.
Position;- Each testis
lies dorso laterally in the 4th & 5th abdominal segments, being embedded
in fat body.
Structure:- Each testis
is 3 lobed & consists of numerous small, whitish, transparent follicles.
The follicles
discharge sperms into the vasa differentia.
Vasa differentia:-
The paired thin,
thread like vasa differentia one from each testis run posteriorly &
downwards to open into the ejaculatory duct.
Ejaculatory duct;-
It is an
elongated, wide duct.
Position;- Ejaculatory
duct is median in position & it runs backward in the abdomen & opens
out by gonopore.
Function;- The
glandular wall of this duct secretes the middle layer of spermatophore.
Utricular /Mushroom shaped
gland:-
It is a large,
whitish accessory reproductive gland.
Position;- Situated at
the junction of vasa differentia & ejaculatory duct.
Structure;- It has a mass of
glandular tubules which are of 3 kinds.
Phallic gland;-
It is a large,
multilobed, leaf like or club shaped gland.
Position;- Phallic
gland is situated below the ejaculatory duct.
Function:- It secretes
the outer layer of spermatophore.
Genital pouch:-
It lies at the
hind end of the abdomen bounded dorsally by 9th & 10th terga &
ventrally by 9th sternum.
It contains dorsal
anus, ventral genital pore, & gonapophyses.
External genitalia:-
In the genital
pouch, surrounding male genital pore, are present phallic organs or
gonapophyses which help in copulation.
These consists of
3 small, irregular, chitinous plates known as phallomeres.
The female
reproductive system of Periplaneta sp. consists
of a pair of ovary, oviducts, vagina,
genital pouch, collaterial glands, spermatheca & external genitalia.
Ovaries:-
No.:- A pair of yellow coloured ovaries
present.
Position:- They lie in 2nd to 6th abdominal
segments one in either side of hindgut, embedded in fat bodies.
Structure:- Each ovary consists of 8 elongated tapering, beaded, blind tubes
called ovarioles.
Each ovariole
include the following parts:-
Oviduct:-
The stalk of 8
ovarioles on one side join to form an oviduct which is lateral, small &
with muscular wall.
Vagina:-
Both the lateral
oviduct unite to form a broad median common oviduct called vagina.
It opens by the
female gonopore into the genital chamber.
Genital pouch/ Gynatrium:-
A large boat
shaped structure whose floor is formed by 7th sternite, roof & sides are
formed by the 8th & 9th sternite.
It can be divided
into a genital chamber (vagina
opens)& an oothecal chamber (oothecae are formed) .
Collaterial glands:-
There is a pair of
white, much branched collaterial glands behind & above the ovaries. Left
gland is opaque & more developed while the right one is transparent &
less developed. They open into genital pouch through separate openings.
Their secretion
forms the ootheca around groups of eggs.
Spermatheca:-
The spermatheca
consists of a left sac like & right filamentous caecum. It opens in the
genital pouch at the tip of a small spermathecal papillae.
Spermatheca
receives spermatozoa during copulation.
External genitalia:-
A sclerite around
the female genital pore is called valvular plate. Besides 3 pairs of plate
like chitinous gonapophyses are present between the female genital pore &
anus.
These assist in
copulation, in laying eggs & in the formation of ootheca.
The digestive
system of Periplaneta sp . consists of
the alimentary canal & digestive glands.
It is a long &
somewhat coiled tube divisible into 3 regions;
foregut, midgut & hindgut.
It includes mouth, mouth cavity, pharynx, oesophagus, crop
& gizzard.
True mouth is a
small opening at the base of the preoral cavity.
Mouth cavity is a small, ill defined
space in front of mouth, surrounded by
mouth parts.
Food is crushed
& acted upon by the salivary secretion here.
It is short &
tubular & its cuticular lining is more folded posteriorly.
From pharynx
arises a long, straight, laterally compressed tube, the oesophagus.
It is a large,
thin walled, muscular, pear shaped sac after the oesophagus.
It serves as a
reservoir of food.
It is a small,
cone shaped, muscular & thick walled chamber behind the crop. It consists
of 2 parts:-
It possesses
internally 6 highly chitinised plates called teeth. Behind the teeth there are
thin, less chitinised plates which bear cushion like pads covered with
backwardly directed bristles.
The teeth help in
grinding & the bristles help in straining the food.
The hind part of
the gizzard projects into midgut as a funnel called stomodaeal valve.
It prevent
regurgitation of food from midgut into gizzard.
It is a short
narrow tube of uniform diameter. It is internally lined by glandular
epithelium & serves as true stomach.
Near the junction
of fore & midgut there are 8 hollow slender tubes called hepatic caeca.
They secrete digestive enzymes.
At the junction of
midgut & hindgut there are 80 to 90 thread like, yellow coloured blind
tubules, called malpighian tubules.
They are generally
excretory in function.
Relatively broader
posterior part divisible into 3 regions-
Narrow & short
tube behind the midgut. Its lumen has epithelial lining.
This is longer,
wider & slightly coiled tube behind the ileum.
Colon continues
into a small, sac like rectum. Rectal glands are present in the rectal wall
for absorbing water. It opens to the outside through anus.
The salivary glands, the inner lining of midgut & hepatic caeca are the digestive glands of
cockroach.
A pair of salivary
glands on either side of the crop are found associated with the alimentary
canal.
Each gland
consists of 2 leaf like, diffused lobes & a reservoir. They with their
ducts form the salivary apparatus.
Each salivary
gland consists of secretory lobules or acini. Each acinus is formed of 2 types
of cells- zymogenic cells & ductule containing cells. Both of them
secrete saliva.
The inner lining
of mid gut & hepatic caeca also produce digestive juices.
The respiratory
system of Periplaneta is well developed
& elaborate to compensate the absence of respiratory pigment in the blood.
The respiratory
system consists of spiracle/stigmata, tracheae & tracheoles.
No. &
position:-
10 pairs of
spiracles or stigmata are present on the lateral side of the body arranged
segmentally. 2 pairs present on thorax & 8 pairs on abdomen.
Structure:-
Each spiracle is a
slit like aperture guarded by bristles or hair to keep out dirt. It is
surrounded by an annular sclerite, the peritreme.
It has a simple valve which can be closed or opened to regulate the flow
of air.
Each spiracle
internally leads into a short tracheal chamber or atrium from which arises a
main tracheal trunk.
Haemocoel contains
a network of elastic, closed, branching
& silvery white tubes called tracheae.
The wall of each
trachea consists of 3 layers- taenidia/ intima,
basement membrane, & epithelium.
There are 3 pairs
of longitudinal tracheal trunks- 1 dorsal, 1 ventral, & 1 lateral in
position. All these trunks are connected by transverse commissures, forming a
network which reaches to every part of
the body.
The profusely
branching tracheae anastomose & penetrate to all parts of the body. The
ultimate finer branches are called tracheoles. Tracheoles come in contact with
the individual body cells. Their cavity are intracellular & lined by
trachein protein. Tips of tracheoles are usually filled with a fluid in which
O2 dissolves & diffuses to tissues.
Mechanism of respiration:-
Alternate
contraction & relaxation of the tergo-sternal muscles causes exhalation
& inhalation of air through tracheae as well as spiracles.
The 1st thoracic
& 1st abdominal pairs of spiracles remain open all the time while the
remaining 8 pairs open only during inspiration.
Air enters the
spiracles during inspiration & comes to the tracheae, then comes to the
tracheoles which contains fluids. Now
the O2 get dissolved in the fluid & reaches to the tissue cells.
Some of the CO2
leaves the body through tracheae & spiracles. But the major portion of CO2
leaves through the cuticular covering of the body.
Corpora allata
(JH) & corpora cardiaca.
2. What is mushroom/ utricular gland? State its function.
It is a large,
whitish accessory reproductive gland.
Position;- Situated at the
junction of vasa differentia & ejaculatory duct.
Structure;- It has a mass
of glandular tubules which are of 3 kinds.
Utriculi majors,
utriculi breviores & seminal vesicles.
Function:-
Thank you for providing valuable information about Periplanata americana . This will be helpful for my entrance exam.
ReplyDeletethanks fr dis good info abt cockroach.. really helped me alot..
ReplyDeletethanks fr dis good info abt cockroach.. really helped me alot..
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