Invertebrate Animals

Second year Students

Dr. Hamza Ahmad Elshabaka

Professor of Embryology

By

Department of Zoology

Phylum: Echinodermata

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Phylum: Echinodermata

General characters:

1-They are entirely marine invertebrates and sexes are

separate.

2-They lack a head or brain and with poorly developed

sensory organs.

3-They possess a dermal endoskeleton of calcareous

ossicles.

4-They are radially pentamerous symmetrical animals but

the larval stage shows bilaterally symmetry.

5-The water vascular system opens into a tube feet which

are used for locomotion, respiration and food collection.

Phylum: Echinodermata

Subphylum: Eleutherozoa

I- Class: Asteroidea

Astropecten relitaris (The Sea Star)

General characters

1- The body is star-shaped

with a central disc and five

triangular flexible arms.

2- The oral surface bears the mouth opening

which is surrounded by a soft peristome.

3- There are 5 ambulacral grooves extend out

from the mouth along the arms.

4- There are a series of conical tube feet along

each ambulacral groove.

5- On the aboral surface, there is a circular

perforated plate called the madreporite.

Aboral surface

Oral surface

Arm

Central disc

Arm

mouth

Ambulacral

groove

Pores of

tube feet

II-Class: Ophiuroidea

Ophiocoma scolopendrina

General characters

1- The body consists of a

small central disc and 5 long

slender arms.

2- The oral surface bears mouth

opening and the madreporite.

3- Each arm is surrounded by 4

longitudinal rows of skeletal plates; an

upper, 2 lateral and a lower plate.

4- Three rows of spines are attached to

the lateral plates.

5- Between the lateral and ventral

plates, a row of tube feets project

on each side.

Aboral surface

Oral surface

Central disc

Arm

Mouth

spines

Arm

Spines

Central disc

Madreporite

(The Brittle Star)

III-Class: Echinoidea

Tripneustes gratilla

(The Regular Sea Urchin)

General characters

1-The body is large,

globular, without arms, with a

lower compressed oral pole and

an upper aboral pole.

2- The body surface is covered by spines

and small pedicellarae.

3- Among spines, numerous tube feet

project on 5 areas extending meridionally

between the 2 poles.

4- The oral pole bears the mouth opening

and 5 strong teeth.

5- On the oral pole there are 5 pairs of

buccal tube feet.

6- In aboral pole, there is a periproct

area through which the anus

opens.

Aboral surface (denuded)

Oral surface (denuded)

Mouth

Ambulacral area

Interambulacral area

Spine bosses

Clypeaster audouini

(The Cake-Urchin)

Oral surface

Aboral surface

General characters

1- The body is much flattened and

not rounded bu exhibits bilaterally

symmetry.

2- The oral surface is flat, covered with short spines

and pedicellariae.

3- The mouth lies at the centre of oral surface and from

it 5 ambulacral grooves fringed with rows of tube feet.

4-The anus lies on the oral surface.

5- The aboral surface is slightly convex and

contains minute spines.

Ambulacral

groove

Mouth

anus

Ambulacral area

Interambulacral area

Petaloids

Class: Holothuroidea

Holothuria curiosa

General characters

1- The body is cylindrical and soft.

2- The mouth and anus lie at the opposite ends of

the body.

3- Numerous tube feet are scattered all over the body.

4- The mouth is surrounded by a circle of buccal

tentacles.

Lovenia elongata

(The Heart-Urchin)

General characters

1- The body is heart- shaped and bilaterally

symmetrical.

2- The oral surface contains the mouth and 5 ambulacral

areas radiate out from it beside some buccal tube

feet projecting only in the area surrounding the mouth.

3- On the aboral surface, broad respiratory tube feet

are found.

Spines

Oral surface

anus

mouth

Peristome Oral tentacles

(The Sea Cucumber)

Subphylum: Pelmatozoa

Class: Crinoidea

Heterometra savignyi

Oral surface

Arms

Mouth calyx

Ambulacral groove

(The Sea Feather)

Oral surface

General characters

1- The body is composed of a cup-like calyx

surrounded by 5 arms. Each arm bifurcates twice, thus 20

long arms are formed.

2- Each arm is fringed with a double series of short branches; the

pinnules.

3- The mouth opening lies at the centre of the oral surface and from

it 5 food grooves radiate out toward the edge of calyx.

4- The anus opens on the oral surface.

5- The aboral surface is covered by a circular

plate with numerous cirri.