Second year Students

Dr. Hamza Ahmad Elshabaka

Professor of Embryology

By

Department of Zoology

Phylum: Arthropoda

For

Invertebrate Animals

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Hamzashabaka @ gmail.com

1-Arthropods display a high degree of metameric

segmentation.

2-The body is divided into head, thorax and abdomen.

In some animals, the head fuses with thorax to form

a tagma called the cephalothorax.

3-In all arthropods, the body is usually covered by an

exoskeleton, or cuticle, that contains chitin.

4-Arthropods periodically undergo molting; the

shedding of the outer cuticular layer.

5-Many arthropods possess compound eyes.

6-The circulatory system of arthropods is open; their

blood flows through cavities between the internal

organs and not through closed vessels.

7-The nervous system is a double chain of segmented

ganglia running along the animals ventral surface.

At the anterior end are three fused pairs of dorsal

ganglia, which constitute the brain.

8-The sexes are mostly separate.

9-Most arthropods have anterior photoreceptors.

Phylum Arthropoda

General characters:

Phylum: Arthropoda

Subphylum: Onychophora

Peripatus

Subphylum: Trilobitomorpha

Trilobite (fossil)

General characters

1-This subphylum includes extinct arthropods.

2-The trilobites are considered the most primitive

arthropod group.

2- The body was divided into head, trunk and

pygidium.

3- The head was covered dorsally by a carapace.

4- Two longitudinally furrows passed through

the whole body dividing it into three

lobes; median or axial lobe and to lateral

or pleural lobes.

Axial

lobe

Dorsal view

Head

Thorax

Abdomen

(pygidium)

Lateral

lobe

Trunk appendages

Preantenna

HeadTrunk

Compound

eye

General characters

1-The body is not divided into segments.

2- The body is covered externally by a chitinous cuticle

which is moulted periodically. The colour may be green,

blue, dark grey or black.

3- The head bears a pair of large fleshy preantennae and

a pair of simple eyes.

4- Walking legs are not jointed and each terminating in a

pair of horny claws

Penaeus japonicus

External features

Class1: Malacostraca

Subphylum: Crustacea

General characters

1-The body is divided into an anterior cephalothorax

and a posterior abdomen.

2- The cephalothorax is covered by a carapce which extends

anteriorly to form a rostrum.

3- The cephalothorax carries 2 eyes on both sides of rostrum.

4- The abdomen consists of 6 segments and ends by a telson.

5- There are 13 pairs of appendages attached to cephalothorax.

6- The abdomen carries 6 pairs of appendages

(The Prawn)

Order 1: Decapoda

pereiopodcheliped

Third

maxillipedSecond

maxilliped

First

maxilliped

Abdominal appendages: 6 pairs

pleopod uropods

male female

Thoracic appendages: 8 pairs

gonopods

A- Uropods (6th abdominal):

a- Each consists of a protopodite and flattened

exopodite and endopodite.

B- Pleopods (5th, 4th, 3rd and 2nd abdominal:

a-The protopodite consists of coxopodite and basipodite.

b- The exopodite and endpodite are large and flattened.

C- Gonopods (1st abdominal):

a-The protopodite consists of coxopodite and basipodite.

b- The exopodite is flattened.

c- The endopodite:

- In the female, it is greatly reduced.

- In the male, it is thin folded flap which unites with the

opposite one to form petasma.

A- Pereiopods (8th, 7th, thoracic):

a-The protopodite consists of coxopodite and basipodite.

b- The exopodite is reduced.

c- The endopodite is cylinderical and formed of 5 podomeres.

B- Chelipeds (6th, 5th, and 4th thoracic):

a- The protopodite consists of coxopodite and basipodite.

b- The exopodite is reduced.

c- The endopodite is cylindrical, formed of 5 podomeres in

which the last two form a pincer or chela.

C- 3rd maxillipeds (3rd thoracic):

a- The protopodite consists of coxopodite

and basipodite.

b- The exopodite is segmented with long bristles.

c- The endopodite is composed of 5 segments.

D- 2nd maxillipeds (2nd thoracic):

a- The protopodite consists of coxopodite and basipodite.

b- The exopodite is segmented with long bristles.

c- The endopodite consists of 5 segments and curved inwards.

E- 1st maxillipeds (1st thoracic):

a- The protopodite consists of coxopodite and basipodite

and carries a broad foliaceous epipodite.

b- The exopodite is broad and flattened.

c- The endopodite is filamentous and reduced.

mandible

Second

antenna

Second

maxilla

Cephalic appendages: 5 pairs

First

antenna

First

maxilla

A- 2nd maxillae (5th cephalic):

a-The protopodite consists of coxopodite,

basipodite & a broad epipodite.

b- The exopodite forms with epipodite a flattened

scaphognathite.

c- The enodpodite is filamentous and reduced.

B- 1st maxillae or maxillules (4th cephalic):

a-The protopodite consists of flattened coxopodite and basipodite.

b- The exopodite is absent.

c- The endopodite is small and segmented.

C- Mandibles (3rd cephalic):

a- The protopodite is heavy and supported with strong teeth.

b- The exopodite is absent.

c- The endopodite forms a 2-segmented mandibular palp.

D- 2nd antennae (2nd cephalic):

a- The protopodite consists of coxopodite and basipodite.

b- The exopodite is abroad plate called squame.

c- The endopodite is filamentous and forms a segmented feeler.

E- 1st antennae or antenules (1st cephalic):

a-The protopodite consists of 3 segments in which the first

segment forms the orbit and the eye-brush arises

on its inner edge.

b-The exopodite and endopodite are short

and segmented.

Different systems of Penaeus

The heart lies in the mid-dorsal side of thorax.

It is a small triangular In shape and with 3 pairs

of ostia, two on dorsal and one on the

posterior side.

FemaleMale

a-The reproductive system consists of 2 testes in the male

and two ovaries in the female.

b- Both testes and ovaries are composed of broad anterior

lobed portions and posterior long narrow ones.

The heart

The reproductive system

Anterior

portion

of ovary

Posterior

portion

of ovary

Anterior portion

of testis

posterior portion

of testis

Ostia

Dorsal side

The mouth leads to a short oesophagus which opens

in the stomach. The stomach is divided into an anterior

cardiac portion and a narrow pyloric one. The pyloric portion

leads to a short narrow mesentron. Two large lobed digestive

glands lie one on either side of the mesentron. The mesentron

leads to the proctodaeum which opens by the anus opening on the

ventral side of the telson.

The digestive system

The nervous system consists of pairs of segmental

nerve ganglia joined together by a double nerve cord.

These ganglia include:

a- Cerebral ganglia.

b- Suboesophogeal ganglia.

c- Six free thoracic ganglia.

d- Six free abdominal ganglia.

The nervous system

Cerebral ganglia

Suboesophageal

ganglion

Thoracic ganglia

Abdominal

ganglia

proctodaeum

Stomach

mesenteron

Digestive

gland

Nervous system

Digestive system

Procambarus clarkii

Neptunus pelagicus

General characters

1- The body is dark red in color.

2- The body is divided into cephalothorax and

abdomen.

3- There are 5 pairs of walking legs, the first of which are

large pincers used for feeding. There are also five pairs of

smaller appendages called swimmerets on the abdomen.

4-The most posterior pair of appendages are called uropods.

Uropods are flat, broad extentions that surround the

telson, which is the last abdominal segment.

General characters

1-The body is divided into cephalothorax

and abdomen.The cephalothorax is covered by a

horizontal carapace.

2-The last 5 pairs of thoracic appendages are uniramous.

3-The fourth thoracic appendages, the chelipeds, possess

large chelae.

4-The 5th, 6th and 7th pairs of thoracic appendages are walking

legs & the last pair terminates in broad paddles.

6-The abdomen in the male is narrow, 4 segments with 2

pairs of uniramous appendages. In the female, ithe

abdomen is broad, 6 segments with 4 pairs

of biramous appendages.

Dorsal view

Ventral view (female)

Thoracic

appendages

cephalothorax carapace

abdomen

cheliped

(The Crab)

Ventral view (male)

Dorsal view

Cephalothorax

Abdomen

Uropod

Cheliped

Antenna

8th thoracic appendage

Pagurus tinctor

General characters

1- The body divided into cephalothorax

and abdomen.

2- The chelipeds (the 4th thoracic appendages)

are asymmetrical as the left chela is much

larger.

4-The abdomen is fleshy and twisted.

5-The abdominal appendages are small and

abscent on the right side.

6- The last pair of abdominal

appendages is hook-like.

Eye

Thoracic

appendages

Lateral view

Dorsal view

Cephalothorax

Left

cheliped

Thoracic

appendage

Shell

Right

cheliped

(The Hermit Crab)

AntennaCephalothorax

Abdomial appendages

6th abdominal

appendage

Nauplius larva

of Penaeus

Zoaea larva

of Neptunus

Antenna

Thoracic

appendages

Abdomen

Telson

Antennule

Antenna

Mandible

Dorsal spine

General characters

1- The body is oval, unsegmented

and with a simple median eye.

2- The body carries three pairs of

appendages. The first pair is uniramous

and the other two pairs are biramous.

General characters

1- The body is divided into

cephalothorax and abdomen.

2- The cephalothorax carries two large

compound stalked eyes, a pair of maxillae,

a pair of maxillipeds and rudiments of five

pairs of thoracic appendages.

3- The abdomen is segmented, ending by a

forked telson and carries 6 pairs of small

appendages.

4- On the dorsal surface of cephalothorax

there is a long dorsal spine.

Terminal seta

Mysis larva of Penaeus

Order 2: Isopoda

Ligia sp.

Thoracic appendagesAbdominal

appendages

Uropod

Abdomen

CephalothoraxEye Antenna

Head

Eye

Antenna

Thorax

Abdomen

Dorsal view

Abdominal

appendage

Rostrum

Telson

General characters

1- The larva resembles

the juvenile prawn.

2- The carapace extends

anteriorly to form rostrum.

3- The thoracic and abdominal

appendages are well

daveloped.

General characters

1- The body is segmented, oval-

shaped, dorsoventrally flattened and

divided into head, thorax and abdomen.

2- The head carries 2 sessile eyes, minute

antennules and longer uniramous antennae.

2- The thorax is composed of 8 segments and

the abdomen is formed of 6 segments. The first

thoracic segment is fused with the head. The

carapace is absent.

3- The head carries two sessile eyes, minute

antennules and longer uniramous antennae.

4- Eight pairs of uniramous appendages are

attached to the thoracic segments.

5- Six pairs of appendages are

attached to the abdominal

segments

Class 2: Branchiopoda

Artemia sp.

Male

Daphnia sp.

General characters

1-The body is oval-shaped with

a posterior dorsal spine and divided

into head and trunk regions.

2-The head extends ventrally to form a

beak-like rostrum and carries a single

median sessile eye, 2 antennules and 2

biramous antennae.

4-The posterior region is limbless,

curved ventrally and ends in

a telson.

(Water-Flea)

(The Brine Shrimp)

Female

Head

Thorax

Abdomen

Caudal rami

Head

Trunk Dorsal spine

Eye

Rostrum

Antenna

Antennule

Carapace

Antenna

Antennule

Compound eye

Thoracic appendages

General characters

1-The body is composed

of head, thorax and abdomen.

2-The head carries two compound

eyes, a single median eye and 5

pairs of appendages.

3-The thorax is formed of 12 segments

and carries 11 pairs of leaf-like

appendages.

4-The abdomen is formed of 6

limblesss segments and a

telson with two rami.

ovary

Ephippium

Resting

egg

Class 3: Ostracoda

Cypris sp.

Class 4: Copepoda

Cyclops sp.

Male

General characters

1-The body is small and indistinctly

segmented.

2-The carapace is formed of 2 valves.

3-There are about 7 pairs of appendages;

antenules, antennae, mandibles, maxillules,

maxillae and 2 pairs of trunk limbs.

4- A median eye is located at the base of the

antennae.

5-The trunk ends with two caudal

rami.

General characters

1-The body is divided into

cephalothorax (head fused

with 2 thoracic segments), 5 free

thoracic segments & 3 narrow

abdominal segments.

2-There are 6 pairs of thoracic

appendages The first pair are

maxillpeds, the 2nd 5th are biramous

swimmin limbs while the 6th pair is

uniramous and reduced.

3-The abdomen ends with a

telson carrying two

caudal rami.

Adductor muscle

Trunk appendages

Antenna

Antennule

Median eye

Caudal rami

Geniculate

antennule

Antennule

Cephalothorax

Caudal rami

Antenna

Female

Antenna

Abdomen

Egg-sac

Abdomen

Swimming

appendages

Carapace

(2 valves)

Class 5: Cirripedia

Lepas sp.

Sacculina

Balanus sp.

General characters

1-The body is formed of a preoral

peduncle and a laterally compressed capitulum

2-The capitulum is enclosed by 5 calcareous plates;

a median dorsal carina, a large anterior sculum and

a posterior tergum.

3-The head carries a thick labrum, 2 mandibles, 2

maxilules and 2 maxillae.

4-The thorax consists of 6 indistinct

segments hich carry 6 pairs of appendages.

5-The abdomen is small and limbless

and ends with 2 rami.

General characters

1- Small sessile marine

animal.

2-The body is enclosed completely

by 6 calcareous plates; carina,

rostrum and 4 lateral plates.

3-The upper part is roofed by a pair

of scute and a pair of terga.

peduncle

capitulum

scutum

carina

tergum

Lateral plates

Terga

Scuta

Rostrum

Carina

Lateral and upper views

Lateral view

General characters1- It is a parasitic cirripede which infests crabs

between abdomen and cephalothorax.

2-The body is a simple flattened sac attached by a

short peduncle to the ventral surface of the crabs

abdomen.

3-Sacculina shows no segmentation or

appendages.

Sacculina

(The Goose Barnacle)

(The Rock Barnacle)

Ventral surface of the crab

Subphylum: Chelicerata

Class 1: Merostoma

Subclass: Xiphosura

Limulus polyphemus

Ventral view

Dorsolateral view

General characters

1- The prosoma has an unsegmented

carapace.

2- The opisthosma is divided into anterior

mesosoma of 6 segments and a posterior

metasoma of 3 fused segments and a telson.

3-The horseshoe-shaped carapace of prosoma

bears a pair of lateral compound eyes and a pair

of anterior median ocelli.

4- Limulus possesses three jointed chelate

chelcera followed by 5 pairs of appendages

all of which are chelate except the fifth

which bears terminal spines.

Caudal cpine

prosoma

Lateral eye

carapace

opisthosoma

Mesosoma

metasoma

chelicera

Walking legs

Class 2: Arachnida

Order 1: Scorpionida

Buthus quinquestriatus

General characters

1- The body is divided into an anterior

prosoma (cephalothorax) and opisthosoma

which is divided into a broad mesosoma of 6

segments and a metasoma of 6 cylindrical segments.

2- The last segment of metasoma ends with the

telson in the form of a vesicle with a sting.

3- The prosoma carries a pair of median eyes and

6 pairs of appendages; one pair of chlicerae,

one pair of pedipalps and 4 pairs of

walking legs.

pedipalp

mesosoma

prosoma

Metasoma

sting

Anus

pecyen

stigmata

Median eyes

Dorsal view

Ventral view

(The Scorpion)

L.S. of lung book

Chelicera

Respiratory lamellae

Air chamber

Order 2: Pseudoscorpionida

Chelifer sp.

General characters

1-The color of the body can be yellowish-tan

to dark-brown.

2- The body is composed of an anterior prosoma and a

posterior opisthosoma.

3- The prosoma is covered by a carapace and contains two

pairs of lateral eyes, 2 chelicerea, 2 large chelated

pedipalps and four pairs of walking legs.

4- The opisthosoma consists of12 broad flat

segments.

Order 3:Solifuga

Galeodes arabs

General characters

1- The body is divided into an anterior

prosoma and a posterior opisthosoma.

2- The prosoma consists of an anterior unsegmented

portion and two posterior segments.

3- The prosoma carries 2 eyes, 6 pairs of appendages;

one pair of chelicerae, one pair of pedipalps and four

pars of walking legs.

4- The large oval-shaped opisthosoma consists

of 10 segments.The first segment is

constricted to form a junction

with prosoma.

opisthosoma

prosoma

pedipalp

chelicera

Dorsal view

Walking

legs

(The Sun Spider)

Chelicera

Prosoma

Walking legs

Opithosoma

Dorsal view

Pedipalp

Order 4: Araneida

Lycosa ferox

General characters

1- The body is divided into 2

unsegmented portions; the prosoma and

the opisthosoma which are connected together

by a narrow waist.

2- The prosoma carries 6 pairs of appendages; one

pair of chelicerae, one pair of pedipalps and 4

pairs of walking legs.

3- The opisthosoma is soft and covered

with hairs.

opisthosoma

prosoma

chelicera

Walking

legs

Pedipalp(The Wolf Spider)

Order 5: Acarina

Argas persicus

(The Soft Tick) Capitulum

Walking legs

Anus

General characters

1- The body is oval-shaped and

dorsoventrally flattened.

2- The prosoma and opisthosoma are fused.

3- The capitulum is a prolongation of prosoma

which carries one pair of pedipalps and a median

proboscis. It arises on the ventral side and does

not project in front of the anterior body margin.

4- Argas possesses 4 pairs of walking legs

each ends in two claws and an adhesive

pad.

Genital opening

Waist

Pedipalp of maleDorsal view

Palpal

organ

Rhipicephalus sanguineus

General characters

1- The body is oval and the

capitulum is terminal and

projects anteriorly in front of the

body.

2- The animal possesses 4 pairs of

clawed walking legs.

3-Two eyes are found, one on

eithe side of the scutum.

(The Hard Tick)

Male

Ventral view

Female

Capitulum

Pedipalp

Walking legs

Anus

Adanal shield

Basis

capitulum

Pedipalp

Walking legs

Anus

Scutum

Chelicera

Basis capitum

Dorsal view

Chelicera Capitulum

Capitulum

Larval stage

Pycnogonum sp.

Class: Pycnogonida

Subphylum: Uniramia

Julus terrestris

Class: Diplopoda

General characters

1- The body is cylindrical, blackish

brown in colour and is divided into head,

thorax and abdomen.

2- The head is small, covered dorsally by a cephalic

shield and carries 2 antennae and 2 clumps of ocelli.

3- The thorax consists of 4 segments each carrying a

pair of appendages.

4- The abdomen is formed of a large number of double

segments and each segment carries 2 pairs of

walking legs.

5- The last abdominal segment ends

with a terminal spine.

abdomen

Walking legs

head

thorax

General characters

1- These are marine spider-like

arthropods.

2-The body consists of cephalothorax and a

rudimentary abdomen.

3- The cephalothorax bears 4 pairs of short,

heavy appendages.

4- The rudimentary abdomen is devoid of

appendages.

5- Sexes are separate.

Cephalothorax

Abdomen

Appendages

Dorsal view

Lateral view

(The Wire Worm)

(Sea spider)

Isolated abdominal

segment

Tergum

Claws

Sternum

Class: Chilopoda

Scolopendra morsitans

Dorsal view Ventral view

General characters1- The body is elongated , dorsoventrally

flattened and divided into head and trunk regions.

2-The head is covered dorsally by a cephalic shield

and possesses two antennae.

3-The trunk carries 21 pairs of walking legs and the last

pair is longer and extends backward.

4- There are two groups of eyes on the head close to

the bases of the antennae.

Head

Antenna

Walking legs

Claw

Trunk

Mandible