4. Why is it chosen for detailed study ?
Because:-
• It is large
• Easily available
• Its characters help in understanding the organization of
other crustaceans.
-
The prawn
5. External features
Body regions
Cephalothorax Abdomen
- Consists of 6 jointed
segments
- Ends with terminal
telson
Head Thorax
-
( 6 segments ) ( 8 segments )
( 5 segments in adult stage)
- Has no external segmentation -Has no visible dorsal or lateral
segmentation
-Has ventral segmentation
6.
7. -The carapace :
• Is a strong shield covers the cephalothorax
-The cardiostegite:
• It is the dorsal part of the carapace
• It lies between two branchiocardiac grooves
• It overlies the heart
-The branchiostegites :
Are the lateral parts of the carapace which cover the
gills
branchiostegites
8. Grooves on the carapace
1- Cervical grooves:
-Two v-shaped
- One on each side of the carapace
- Demark between head and thorax.
2- Branchiocardiac grooves:
-Two grooves bound the cardiostegite
.
Branchiocardiac grooves
9. The abdomen
•Consists of 6 segments
terminates with telson
•Each segment is covered by an
exoskeleton of welded scelerites:
Dorsal tergum, ventral sternum
& lateral pleurites
•Mid-dorsally the tergites
produce the carina
•Between the abdominal
segments there are arthrodial
membranes & series of peg and
socket hinges
10. Structure of the
appendage
Coxopodite
forms
Basipodite
• 19 modified pairs of biramous
modified appendages.
• A pair for each body segment
• Note :- serial homology
The appendages have homologous
structure but modified in different ways
to perform different functions
Carries 2 ramai
exopodite
endopodite
The appendages
Basal stem
( protopodite)
11. • Antennules
(1st antennae)
• 2nd Antennae
• Mandibles
• Maxillules
• Maxillae
• Touch- taste- balance
( with a statocyst at the basal segment of its protopodite)
• Touch and taste
• Crushing food
• Holding food
• Holding food - production of respiratory current
I- Cephalic
appendages
5 pairs
Function
15. Swimming legs
1- Gonopods (1 pair)
on 1st abdominal seg.
= (15th body seg.)
2-Pleopods (4 pairs)
on 2nd 3rd 4th 5th abdominal seg.
= (16th 17th 18th 19th body seg.)
3-Uropods (1 pair)
on 6th abdominal seg.
= ( 20th body segment)
To distinguish between sexes
In female the gonopods are with reduced endopodite
In male the two endopodites of the gonopods fused
forming a copulatory apparatus called petasma
Swimming
Backward swimming
Abdominal appendages
(6 pairs)
Function
17. I- The body wall
Is dermal consists of:-
1- The cuticle:- which consists of
a- Epicuticle
Exocuticle
b- Procuticle
Endocuticle
2- The epidermis
The dermis
The muscular system
18. -The muscular system:
- segmentally arranged stout bundles of striated muscles
- These muscles serve in support and movement
There are two groups of muscles :
- Dorsal extensor muscles ( (
باسطه straighten the body .
- Larger flexor muscles ( )قابضه bend the body.
19. Open circulatory system ( with arteries – blood sinuses )
It is made up of:
•It is small muscular heart situated
in the dorsal region of the thorax
•It has 3 paired ostia guarded by
valves which open inwards
•Cavities filled with
blood around the
organs
1-Heart
2-Sinuses
3- Six arteries
4-The blood
•Contains amoeboid cells & respiratory pigments called
haemocyanin that turned blue when blood is oxygenated
20. •Each gill consists of:
1- Stem ( gill axis )
2- A large number of primary branches on each side
of the axis. (gill filaments)
( These branches are curved in half a circle and give
off minute branched gill filaments on their outer
edges .(
3-The gill axis contains two blood channels
afferent & efferent branchial vesseles
21. Excretory system
•Excretion takes place by green
glands (antennary glands)
• There is a pair of green glands
situated behind the 2nd antennae
and opens at its base.
•Each green gland consists of
• 1-Dorsal sac ( bladder ) .
•2- Coiled tubule
•3- Labyrinth of green cortex
ends
by end sac
22. Nervous system
It is formed of segmental ganglia joined together with
double nerve cord
It consists of:
1- Cerebral ganglia = (Supra-oesophageal ganglia)
2- Sub-oesophageal ganglion
3- Six pairs of free thoracic ganglia
Ventral nerve cord
4-Six pairs of fused abdominal ganglia
