Phylum Arthropoda: Classification and Characteristics of Penaeus monodon

Tanvir Hosen Monowara mishu
Tanvir
Hosen
Monowara
Mishu

 Arthropoda: Arthropoda are triplobastic,
bilaterally symmetrical, metamerically
segmented animals with coelom which is reduced
and modified. Their body is covered with a thick
chitinous exoskeleton which moults periodically
and their appendages are jointed and without
true nephridia and cilia in their structure.
 Example: (i) Penaeus monodon; (ii) Hippa sp

 The name arthropods means, “Jointed Legs” and refers
to the most characteristics structure of them. It is,
therefore the jointed structure of them. The jointed
structure of limbs which has earned the name
Arthropoda (GK, arthros = jointed; podos = foot) for
this phylum.

 Arthropod are triplobastic, bilaterally
symmetrical, metamerically segmented animals.
 Digestive tract is complete, mouth and anus lie
at opposite ends of the body.
 Circulatory system is open with dorsal heart and
arteries but without capillaries.
 Fertilization is internal, development is usually
indirect through larval stages.
 Cilia are entirely absent from all parts of the
body.

 Cylops sp.
 Nebalia sp.
 Mysis sp.
 Penaeus monodon
 Cancer sp.
 Sqilla sp.
 Hippa sp.
 Balanus sp.

 Phylum: Arthropoda
 Subphylum: Mandibulata
 Class: Crustacea
 Sub-class: Malacostraca
 Order: Decapoda
 Sub-order: Natantia
 Section: Penaeidae
 Genus: Penaeus
 Species: P. monodon

 Phylum: Arthropoda
 Subphylum: Mandibulata
 Class: Crustacea
 Sub-class: Malacostraca
 Order: Decapoda
 Sub-order: Natantia
 Section: Caridae
 Genus: Palaemon (Macrobrachium)
 Species: M. rosenbergii

Penaeus monodon inhabits marine and
brackish water environment. It is nocturnal
creature and lies hidden at the bottom
during the day and comes to surface during
night in search of food. It walks slowly at
the bottom with the help of walking legs
and swims actively at the surface with help
of swimmerets (pleopods).

 Penaeus monodon is mainly carnivorous, feeding on
slow moving miscroscopic animals, small crabs,
shrimps, mollusks, marine worms and detritus.
 Pascula (1983) started that unlike fishes Penaeus
monodon are nibblurs and slow eaters. They take food
with their chelae and bring to their mouths and slowly
chew on the food pellets. They throw the whole price
into mouth if the feed is too small. It is experimental
that their feeding activity during low tides, the weak
ones (.e.g. just moulted) are attacked by the healthy
ones.

CLASSIFICATION
Phylum-Arthropoda
Class:
Crusfacea Merostomata Arachnida Mariapoda Insecta

 Characters:
 Body is covered externally by a chitinous cuticle.
 Excretory organs are modified coelomoducts forming
maxillaryor antennary (green) glands. Malpighian
tubules are absent.
 Digestive tract is almost straight
 Respiration occurs usually by gills.
 The crustacean are unisexual.
 Example: Branchipus Pinaeus monodon

 Characters:
 Aquatic and marine chelicerates, with branchial
respiration.
 Antennae are absent
 Excretion by a pair of coxal glands. No malpighian
tubules.
 Body divisible into two regions, anterior prosomay
cephalothrax and posterior opisthosoma/ abdomen
 Prosoma dorsally 2 lateral compound eyes and 2
median simple eyes.
 Example: Limulus Eurypterus.

Characters:
They are generally small, air-breathing,
mostly terrestrial and solitary arthropods.
Which are especially abundant in the warm
dry regions.
The great majority are free-living,
predaceous or parasitic.
There is no luad. The body is composed of
two divisions cephalothrox and abdomen.

 The cephalothroax bears simple and
sessile eyes and six pairs of jointed limbs
comprising one pair of preoral cheliceral.
One pair of postoral pedialpi and 4 pairs
of walking legs. The antennae and the
true jaws are entirely absent the
abdomen is usually limbuss but sometimes
ends in a telson.
 Cuticle is often provided with sensory hair
or scales.
 Example: Buthus Cryptocellus

Characters:
 A small group of terrestrial, secretive, air-breathing
arthropods, wholly absent from the sea.
 Digestive tract simple, straight
 Sexes separate. Gonad Single but gonoducts paired .
 Nervous system not concentrated
 The eyes are ocelli.
 Example: Polyxenus geophilus

 Characters:
 Air breathing mostly terrestrial and aerial and rarely
aquatic arthropods, minute to moderate in size.
 The body is metamerically segmented, bilaterally
symmetrical and dived into three district regions-lead,
thorax and abdomen.
 A liver is absent but salivary glands are often present.
 The abdomen is distinctly divided into 7-11 segments.
 Fertilization is usually internal.
 Example: Silverfish pulex

 The following life cycle of Penaeus monodon is typical of other penaeids as
well:

Adult P. monodon are bottom dwellers
in the offshore areas at depths of 20 to
70 meters. The life cycle starts with
the spawning or release of
approximately 5,00,000 eggs by a
gravid or ripe female. The larvae
hatched out 12-15 hrs after spawning,
looking very different from the adults.
After 10-12 days and two more larval
stages. The larvae metamorphose into
the post larvae.

 The young post larvae or fry move shoreward
and start appearing in coastal waters around
two weeks into their post larval life. They
continue migration towards mangrove and
other brackish water areas which serve as
their nurseries or feeding groups, growing to
larger juveniles, post juveniles and sub
adults. At this stage P. monodon is mainly
carnivorous, feeding on slow moving
microscopic animals. Small crabs, shrimps,
mollusks, marine worms and detritus.

 Although first mating occurs in the estuaries,
it is only during or after migration back to
the offshore areas that full ripening of the
ovaries takes place. First spawning occurs at
10 months of age upon arrival in the offshore
areas, followed by 2-3 more consecutive
spawning within a single season. The adult
remain in the ocean upto a ripe old stage of
3, 4, 5 years unless they die earlier of
predation or disease. However, some
metapenaeus species reportedly undergo
spawning and the larval stage in brackish
water areas, completing the life cycle
without returning to the open sea.

 A pear-shaped ink sac lies over the posterior
ventral surface of visceral dome and opens
by a duct dorsally into the rectum close to
the anus. The terminal part of the duct
forms on ejecting ampulla. The ink-gland,
lying inside the wall of the large ink-sac,
contains a high concentration of melanin
pigment and is stored in the ink-sac. When
the cuttle fish started, it discharges the ink
through the funnel as a black cloud, which
forms a sort of smoke screen, under the
cover of which the animal escapes from an
enemy or approaches a prey.

 Shape and size: The body of P. monodon is
elongated, more or less spindle shaped and
bilaterally symmetrical. The size of the adult is
generally 25 to 38 cm in length.
 Colouration: Pattern of color is variable. Usually
the fresh specimens are dark blue to black.
Carapace and abdomen are transversely bended
with grey to reddish brown stripes. Pleopods
fringed with bright red setae. Pleopods and
uropods tipped with light blue color.

 Rostrum: The rostrum is fixed and rigid, double curved
(firstly downward and at the tip slightly upturned). It is
armed with 6-8 dorsal and 2-3 ventral teeth but usually
the rostral formula is 7/3.

 Carapace: The Carapace is smooth and thick. It’s
length is 1.5-1.7 times of breadth. The carapace is
divisible into various regions. It is armed with
spines and marked by grooves (Sulcus) and carina
as given below.
 Carina/Ridge: Castro antennal carina well developed
reaching from antennal to below hepatic spine. Gastro-
orbital carina occupies posterior one third of distance
between post orbital margin of carapace and hepatic spine;
cervical carina well developed, hepatic carina very short and
lies horizontally.
 Sulcus/ groove: Post orbital groove absent, Gastrofrontal
groove present. Gastro-orbital sulcus deep between gastro-
orbital carina and post antennal carina. Cervical and hepatic
sulcus ill-defined.

 Exoskeleton: The entire body and the appendage are
covered by a hard and chitinous cuticle, which forms
exoskeleton. The exoskeleton is hardened by deposit of
salts of lime and colored with various pigments. The
hard pieces of exoskeleton are called selerities, which
are jointed by softer cuticle forming arthrodial
membrane. The cephalothorax consists of a head and
thorax. The head is covered with dorsal plate and thorax
with a carapace.

 Cephalothorax: The cephalothorax is somewhat
cylindrical in shape and is uncounted, no external
segmentation is marked. It is formed by the union
of head comprising five appendages bearing
segments and the thorax comprising 8 segments.
 Abdomen: The abdomen rounded dorsally but
compressed laterally, is jointed, external
segmentation is clearly marked and composed of
six movable segments having terminal conical
piece, telson. The abdomen is often turned
downwards. Each segment of the abdomen carries
a pair of jointed appendages called pleopods or
swimmerets.

 Mouth: It is a mid-ventral slit-like aperture lying at
the anterior end of the cephalothorax.
 Anus: It is longitudinal slit-like aperture lying at the
ventral end of the base of telson.
 Female genital apertures: These are paired each
situated at the inner surface of the coxal of third pair
of walking legs.
 Male genital aperatues: These are also paired each
situated at the inner surface of the coxal of fifth pair
of walking leg.

 In P. monodon the following sex-organs are found:
 Petasma in male
 Thelycum in female.
 Petasma: In the fist pair of pleopod of the adult male of P.
monodon, the endopodite modified into an elongated and
much folded structure. The two halves of this structure are
united along their median margin, forming the male sex
organ-petasma. It is symmetrical and reached into the bases
of the fourth pereipods consisting of two segments ling
dorso-medially clopped together anteriorly by interlocking
process and posteriorly lying in close apposition . during
copulation, the transfer of spermatophores is done trough
petasma.

Embryo: Viable eggs of P. monodon are
spherical, yellowish green in color
somewhat translucent ranging from .27
to .31 mm with an average of .29 cm in
diameter. The 2-celled, 4-celled morula
and embryonic nauplies stages were
approximately .5, 1, 1.8 and 11 hours
after spawning respectively.

 First nauplies: The first nauplies is measured from .30
to .33 mm in total length with .2 mm in body width
with an average of .19 mm. There are three pair of
appendages:
 1st antennareor antennule.
 2nd antennae.
 Mandibles.
 The 1st antennae is uniramous, 2nd antenna is biramous,
and the mandible is biramous.

 2nd Nauplies: The 2nd nauplies is measured from .37
to .38 mm in total length with an average of .35
mm and from .17 to .22 mm in body width with an
average of .19 mm. The major different between 1st
and 2nd nauplies is that most of the long setae on
each appendages become plumoso.

 3rd nauplies: The 3rd nauplies is measured from .36
to .42 mm in total length with an average of .39
mm and from .19 mm to .22 mm in body width
with an average of .20 mm. The body become more
elongated.

 4th nauplies: The nauplies I measured from .34 to
.43 mm in total length with an average of .39 mm
and from .17 to .20 mm average of .19 mm. The
body become cylinder and is elongated posteriorely.
A pair of frontal sense organs are present on the
anterior margin of the body.

 5th nauplies: The fifth nauplies is measured
from .39 to .42 mm with an average of and
width .19 mm.

6th nauplies: The sixth nauplies is
measured from .50 to .58 mm in
total length with an average of .54
mm and from .19 to 21 mm width
with an average of .20 mm. Furcal
development at the posterior end is
more pronounced, and a pair of new
spine grow inside and outside of the
furca resulting in a spine formula of
777.

1st protozoea: The 1st
protozoea measures from .96 to
1.17 mm in total length with an
average of 47 and from .47 to
.58 mm in CL (Carapace length)
with an average of .53 mm and
from .42 mm in carapace width
with an average of .40 mm.

 The 2nd protozoea measures from 1.72 to 2.04
mm in total length and from .70 to .77 mm in
carapace length with an average of .73 mm. The
abdomen is divided into six segments, the telson
is not separated from the 6th.

 The 3rd protozoea measures from 2.97 to 3.30
mm in total length with an average of 3.12 mm
and from 1.14 to 1.21 mm in carapace length
with an average of 1.17 mm.

1st mysis is measured from 3.28 to
4.13 mm in total length and from
1.25 to 1.41 mm in carapace
length with an average of 1.31 mm

 2nd mysis is measured from 4.00 to 4.69 mm in
total length.
 The characteristics of this substages from the 1st
are the development of unsemgnted pleopods
and spine on the antennal blade.

 3rd mysis is measured from 4.05 to 4.87 mm in
total length.
 The distinguishing characteristics of the 3rd
mysis are the appearance of a dorsal spine
(sometimes lacking) on the rostrum and of well
developed pleopods.
 After the mysis stage they jump into post larval
stage.

Ecdysis:The process both of ridding the body of
old exoskeleton or cuticle and of secreting a new
cuticle is called moulting or ecdysis.
Growth and moulting process of
Penaeus monodon:The presence of a thick
and generally inflexible exoskeleton created
problems of growth and locomotion, that had to
be overcome in the evaluation of Arthropods.
The problem of growth has been eliminated by
the phenomenon of moulting which is quite
characteristic of the arthropods.

 The exoskeleton is made of dead matter and
therefore, it can not grow. An the arthropod
grows in size with age, the old exoskeleton is
shed periodically and a new exoskeleton
developed from the underlying hypodermis.
Slightly bigger than its predecessor to
accommodate the increased body. The
process both of riddling the body of old
exoskeleton or cuticle and of secreting a
new cuticle is called moulting or ecdysis.
The ectodermal derivative such as foregut,
hindgut and tracheal and some other parts
are also shed.

The process is under hormonal control and
involves a series of steps as follows:
 Just before actual shedding the hypodermal cells
secrete a moulting fluid containing enzymes
which completely erodes the endocuticle. Thus
the outer hard layer of cuticle becomes loose and
free from the underlying hypodermis.
 Simultaneously, the three layers of the new soft
cuticle are secreted in order beneath the old
exoskeleton by the hypodermis.
 The old exoskeleton splits longitudinally along the
middorsal or lateral sides of the body allowing
the animal to pull out of it.

 The newly emerged animal rapidly grows in body
size by proliferation of cells and absorption of
more water. The new cuticle is relatively soft
and pliable to enable the animal to stretch and
increase in size.
 Soon the new cuticle hardens so that further
increase in body size cannot occur until the next
ecdysis.
 The growth stage between two moult is termed
an instars. The number of instars during growth
period varies of instars during growth period
varies with different species. The animal has
little protection from enemies while the new
cuticle is soft. Frequently the animal goes into
hiding until the new cuticle hardness.

Moutlting apparently does more
than provide for growth, for fully
formed adult crayfishes and
lobster continue to moult
periodically. It is believed that an
additional purpose may be
excretion.

 The digestive system of P. monodon is composed
of alimentary canal and hepatopancreas.
 A. Alimentary canal: The alimentary canal
consist of foregut, midgut and hindgut. The
foregut comprises the mouth, buccal cavity,
oesophagus and stomach.
Mouth:The mouth is a large slit-like aperture
situated mid-ventrally below the anterior end of
head between the third and fourth segments.
Buceal cavity: It is anterior posteriorly
compressed and has thick chitinous lining which
is thrown into irregular folds.

 Oesophagus:The buccal cavity leads into a short
but broad oesophagus. Internally the thick
muscular wall of the oesophagus is thrown into
four prominent longitudinal folds projecting into
the lumen of these folds. The anterior is short
but the posterior and lateral are longer and more
prominent. Each of the lateral folds being
subdivided in two smaller unequal folds.
 Stomach:The oesophagus leads into a spacious
chamber the stomach which occupies most of the
cephalothorasic cavity. It is surrounded laterally,
ventrally and posteriorly by the hepatopancreas.
The stomach is divided into two parts; (a) a large
anterior bag-like cardiac stomach and (b) a very
small pyloric stomach cardiac and pyloric
stomach are separated by a number of valves.

Cardiac stomach:The cardiac stomach is
liner internally with delicate cuticle or
intima. The inner lining of intima is
produced into a very large number
inconspicuous longitudinal folds
covered by minute bristles.
Pyloric stomach: The pyloric stomach is
very small and narrow chamber lying
below the posterior end of the cardiac
stomach. Its walls are thick and
muscular.

 Midgut:The midgut is a long, narrow, straight
and sunder tube running back along the median
line above the mass of the ventral abdominal
muscles upto the sixth abdominal segment.
 Hindgut: The hindgut extends from the
posterior end of the midgut to the anus and
forms the shortest portion of the alimentary
canal.
 Hepatopanereas:The hepatopancreas or the so
called liver is a large bilobed, compact, orange
coloured grandular mass occupying a
considerable area of cephalothoriac cavity. It
lies immediately behind the cardiac stomach.

 Penaeus monodon mainly feeds on algae, moss
and other aquatic weeds and occasionally on
such small aqautic animals as insects, snails, fish
etc. and debris of the bottom. They are more
active at dusk and day-break than at any other
time. The chelate legs aided by the third
maxillepedes, capture and convey the food to
the mouth. The coxae of the second
maxillepedes hold the food. the incisor processes
of mandibles cut it into smaller pieces, which are
swallowed with the help of maxillipedes,
maxillae and maxilliulae.

Course parts are ejected through the
mouth. Inside the buccal cavity, the
molar processes of mandibles
masticlate the food, which is then
conveyed to the cardiac stomach
trough the oesophagnes peristaltic
action of oesophageal wall and the
sucking action of cardiac stomach a the
time of feeding, facilitate the passage
of food through the oesophagus and the
stomach.

 Characters:
1. Essentially aquatic arthropods
2. Size varies from 2.5 mm to 3 meters
3. Body is covered externally by a chitinous
cuticle
4. Body bilaterally symmetrical, triplobastic
and divisible into three regions head, thorax and
abdomen.
5. Head bears a larval median eye.
6. Digestive tract is almost straight
7. Respiration occurs usually by gills.

 There are more than 30,000 known species of
crustaceans, grouped in 8 sub-classes as follows:
Sub-class -1: Cephalocaria
 Most primitive, marine and bottom dwelling
 Body small, sunder and divided into a horseshoe –
shaped head and a trunk of 19 segments.
 Eyes and carapace absent
 Example: Hutchinnoniella.

 Sub-class -2: Branchipoda
 Characters:
 Small, primitive, free-living, mostly fresh water
crustaceans.
 Body made of a varying number of body-segments.
 Cephalic carapace, when present, is either bivalved
or shield-like.
 Order 1. Anostraca (Fairy shrimps)
 Characters:
 Carapace absent
 Eyes stalked
 Antennae uniramous
 Example: Branchipus, Eubranchipus,

 Oder-2: Notostraca (Tadpole shrimps)
 Characters:
 Carapace large and shield-shaped
 Eyes sessile and close together
 Antennae reduced or absent in the male .
 Example: Trips ( = Apus) and lepidurus.
 Order -3: Conchostraca (Class Shrimps)
 Characters:
 Carapace bivalved.
 Eyes sessile.
 Trunk appendages 10 to 32 pairs.
 Example: Lynceus, Cyzicus.

 Sub-class -3: Ostracoda
 Body laterally compressed.
 Body enclosed inbivaled shell.
 Commonly called seed-shrimps.
 Order-1: Myodocopa
 Found in sea water.
 Carapace not notched with apertures for antennae
 Second antennae used in swimming.
 Example -: Cypridina, Phylomedes.

 Order-2: Platycopa
 Marine, carapace unnotched .
 Antennal biramous.
 Trunk appendages single pair.
 Example: Cytherella.
 Order-3: Podo copa
 Marine or freshwater, carapace unnotched.
 Antennae uniramous, clawed at tips.
 Trunk appendages 2 pairs.
 Example: Cypris Drawinula.

 Order-4: Cladocopa
 Second antennae biramous.
 Both pairs of antennae used in swimming.
 Example: polycope.
 Sub-class-4: Mystacocarida
 Primitive, marine.
 Body microscopic, elongated, cylindrical.
 No compound eyes, a nauplies eye present.
 Example: Derocheilocarus typicus.

 Sub-class-5: Copepoda
 Free swimming, commensal or parasitic.
 Body small, elongated, composed of ahead.
 Carapace reduced or absent.
 Example: Cyclops, Monstrilla.
 Order-1: Calanoida
 Mainly found in freshwater lakes, ponds.
 Antennae biramous.
 Example: Calanus,Diaptomus.

 Order-2: Harpicticoida
 Body construction scarce between segments bearing
fourth and fifth legs clearly apparent.
 Antennae biramous.
 Example: Harpacticus.
 Order-3: Cyclopoida
 Found in pond, lakes and also in salt water.
 Antennae uniramous.
 Example: Cyclops.

 Order_4: Monstrilloida
 Larvae parasitic in marine polychate worms.
 Mouth parts and antennae not found.
 Example: Monstrilla.
 Sub-class -6: Branchiura (Fish Liee)
 Body flat, divided into a head, thorax, abdomen.
 One pair of sessile compound eye.
 Mouth is suctorial.
 Examples: Argulus (crab liee), Dolops.

 Sub-class -7: Cirripedia ( Barnacles)
 Body relatively large and imperfectly segmented
 Typically 6 pairs of biramous , cirriform.Thoracic
appendages.
 Abdomen rudimentary , limbuss ,ending in a of pair
caudal styles.
 Odrer-1: Thoracica
 Non-parasitic or commensal, with or without a stalk.
 Thoracic appendages 6 pairs.
 Alimentary canal present.
 Example: Lepas, Balanus.

 Order-2 Acrothoracica
 Minute, sessile, bore into mollusc shells or cordals.
 Naked with reduced mantle.
 Thoracic appendages less, usually 4 pairs.
 Example: Trypetesa, Alcippe,
Crytophialus.
 Order-3: Ascothoracica
 Parasitic on echinoderms and corals.
 Naked with bivalves or reduced mantle.
 Example: Synagoga, Dendrogaster.

 Order-4: Apoda
 Parasitic in mantle cavity of stalked brancle.
 Antennae large, biramous and locomotory.
 Trunk appendages 4 to 6 pairs.
 Example: Daphnia, Sida.
 Sub-class -8: Malacostraca
 Large-sized crustaceans, marine and fresh water.
 Paired compound eyes, stalked or sessile, present.
 Antennules often biramous.
 Example: Nebalia, Mysis.

 Order-1: Nebaliacea
 Primitive marine crustaceans.
 Stalked eyes.
 Telson with a pair of caudal style.
 Example: Nebalia.
 Order-2: Mysidacea
 Marine crustaceans.
 Carapace covers almost entire thorax.
 Example: Mysis.

 Order-3: Isopoda
 Body dorso-ventrally flattened.
 Abdomen is usally short.
 Example: Oniscus.
 Order-4: Decapoda
 Mostly marine forms.
 Statocyst present.
 Example: Astacus.

Prawn Shrimp
Prawn inhabits in freshwater. Shrimp inhabits in marine water .
Blue in color, occasionally they
are brownish with orange stripes.
Pattern of color is variable
carapace and abdomen are
transversely bended with reddish
brown stripes.
The 2nd abdominal pleuron
overlaps the 1st pleura.
The 2nd abdominal pleuron
overlaps only the 3rd pleuron and
is itself overlapped by first.
There are 13 teeth in the lower
part of the rostrum.
There are 6-8 dorsal and 2-3
ventral teeth in the rostrum.
e.g. Macrobrachium rosenbergii. e.g. Penaeus monodon .

Penaeidae Caridea
Pleura of the 2nd abdominal
segment do not overlap those
of the first segment .
Pleura of the 2nd ob abdominal
segment overlap those of the
1st segment.
Third legs usually chelate . Third legs do not chelate.
Carpus of 2nd pair of legs not
annulated.
Carpus of 2nd pair of legs
annulated .
Gills dendrobranchiate . Gills phyllobranchiate .
e.g. Penaeus mondon. e.g. Macrobrachium
rosenbergii.

Male P. monodon Female P. monodon
Present petasma on the 1st
pair of pleopods.
Present thelycum on the 4th
and 5th pair of pleopods .
Genital pore on the base of 5th
pleopods.
Genital pore on the base of 3rd
pleopods.
Appendix masculine on the
2nd pair of pleopods.
No appendix masculine.
Smaller than the female. Larger than the male.
Sexual maturity, male 37 mm
in carapace length.
Female 47 mm in carapace
length.

Phylum Arthropoda: Classification and Characteristics of Penaeus monodon

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Phylum Arthropoda: Classification and Characteristics of Penaeus monodon