3. PHYLLUM :- ECHINODERMATA
General Characters :-
1. They are marine animals.
2. Tribloblastic animals.
3. True coelom is present.
4. Their space is generally pentamerous.
5. The exoskeleton is formed of calcareous plates or ossicles.
6. Generally, spine are found over the body and calcareous plate below the
skin.
7. In Adult condition Body :- Radially symmetrical, but their larvae are
Bilaterally symmetrical.
8. Tube feet are present which are organ of locomotion and also helpful in
food catching & respiration.
4. 9. A water vascular system is found in them.
10. Respiration take place by branchiae.
11. Excretory organs are absent.
12. Sexes are separate.
CLASSIFICATION
• Phylum has been classified into four sub- phylum. (Marshall & Williams)
SUB-PHYLUM :- ECHINOZOA
1. Globoid and cylindrical echinoderm which do not develop arms.
2. Hydrocael forms a ring about the giving rise to meriodional
water vessels.
5. • Class 1 – Helicoplacodea
1. Free living, fusiform placoid echinozoans.
2. Plates of the body form the test.
3. Anal & Oral aperture at opposite poles.
Example :- Helicoplacus.
• Class 2 – Holothuroidea.
1. Body elongated in oral – aboral axis.
2. Skin leathery.
3. Body is long and cylindrical or pentamerous.
4. Mouth and anus are present on opposite surfaces.
5. Mouth surrounded by tentacles.
6. Tube feet are found & helpful in locomotion.
7. Sexes are separated.
6. • Sub-Class 1 – Dendrochioracea
1. Respiratory tree present.
2. Introvert presents or pharyngeal refractor muscles present.
• ORDER 1 – Dactylochirotida
1. Digitate and feebly branched tentacles.
Example :- Ypsilothuridae.
• ORDER 2 – Dendrochirotida
1. Tentacles are elongated, branched to form tree like structure.
Example :- Cucumaria.
• Sub-Class 2 – Aspidochiroatcea
1. Tentacles 10-20 shield shaped.
2. Test vestigial .
3. Tube feet present on ventral side.
7. • ORDER 1 – Aspidochiroatida
1. Large branched respiratory tree.
Example :- Holothuria.
• ORDER 2 – Elasipodida
1. Respiratory tree absent.
Example :- Elpidia, Pelagothuria.
• Sub-Class 3 – Apodacea
1. Holothurian with simple digitate tentacles.
2. Tube feet reduced or absent.
3. No spicules in the skin, no refractor muscle.
8. • Class 3 – Edriosteroidea
1. Free swimming placoid echinozoan with mouth and anus on the upper side
of the test.
2. Five ambulacra radiate from the mouth. Hinged ambulacral ossicles border
the ambulacra, which carry food groove.
3. Body discoidal, dorsovantrally flattened .
4. Extinct forms.
Example :- Edrioaster.
• Class 4 – Exhinoidea
1. Body is oval round or heart shaped without arms but with ambulacral areas.
2. Body enclosed in a test made up of calcareous plates.
3. Pedicilarie are stalked & tree – jawed.
4. Introvert or lantern present.
Example :- Sea urchin.
9. • Sub-Class 1 – Perischoechinoidea
• ORDER 1 – Exhinocytitoida , Example :- Eothuria.
• ORDER 2 – Bothricidaroida , Example :- Bothriocidaris.
• ORDER 3 – Palaechinoidea , Example :- Palaechinus.
• ORDER 4 – Cidaroida , Example :- Miocidaris.
• Sub-Class 2 – Euechinodea
• Super Order 1 – Diaematacea
• ORDER 1 – Echibothuroida
• ORDER 2 – Diadamatoida
• ORDER 3 – Padinoida
• ORDER 4 – Pygasteroida
10. • Super Order 2 – Echinancea
• ORDER 1 – Salenioida
• ORDER 2 – Hemidaroida
• ORDER 3 – Phymosomatoida
• ORDER 4 – Arbacioida
• ORDER 5 – Temnopkuroida.
• ORDER 6 – Schinoida.
• Super Order 3 – Gnathostomata
• ORDER 1 – Holectypoida
• ORDER 2 – Clypeasteroida
• Super Order 4 – Atelostomata
• ORDER 1 – Classiduloida
• ORDER 2 – Holastaoida
• ORDER 3 – Spatangoida
11. • Class 5 –
• Sub – Phylum 1 – Hc
• Includes extinct, dorsovantrally flattened echinoderms, with no signs of radial
symmetry .
• Sub – Phylum 2 – Cri
1. Body aboral, cup shaped.
2. Ambulacra are restricted to the adoral surface.
3. Sessile, atleast in any part of their life.
4. Mouth and anus both are situated on the upper side. Most of the member
are now extinct.
Example :- Antedon.
• Sub – Phylum 3 – Homalozoa
• Sub – Phylum 4 – Crinozoa
• Sub – Phylum 5 – Asterozoa
12. ANTEDON
General Characters :-
1. Commonly known as – “Feather star”
or “Sea lily”.
2. The pentamerous body is disc-shaped
with flower-like appearance.
3. The body is divisible into a central disc
or calyx and a series of 10 radiating
arms.
4. The central disc is differentiated into
convax and upwardly directed oral &
flat ventrally directed aboral surfaces.
5. The animals are highly coloured and
may be green, purple, yellow & red.
13. 6. The oral surface is covered by soft, leathery skin the oral membranes are the
tegmen in which are embedded minute calcareous plates in the form of a
continuous sheet.
7. The mouth is the situated in the central of the oral disc and is surrounded by
five small triangular oral valve.
8. In the between of oral valves radiate five narrow, open and ciliated food
grooves.
9. The anus is situated near the mouth in one inner ambulacrum on a
prominence.
10. A series of five movable long slender arms often branched and bearing
small alternating branches , the pinnules originated from central body.
11. Ambulacral groove ciliated, open runs from mouth on the oral surface of
arms & pinnules their tips.
12. Tube feet reduced generally tentacle like present along the edge of
ambulacral groove.
14. 10. Madreporite is absent.
11. The aboral surface is partly covered by tagmen and partly by a large
flat, pentagonal central sketelal plate , the centro-dorsal ossicles.
12. On the aboral surface are slender curved and cylidrical appendages
known as cirri meant for gripping the substratum.
13. The sexes are separate but there is no sexual dimorphism .
14. The development is indirect with pentacrinoid larva with jointed stalk.
15. They have the power of regeneration .
15. ASTERIAS
General Characters :-
1. It is commonly known as ‘stare fish’.
2. Dorsoventrally flattened star –shaped ,
pentagonal body .
3. Body is divisible into a central disc and five
radiating arms.
4. The animal are usually bright coloured yellow,
brown or orange.
5. The body is divisible into a flat , downwardly
directed and light coloured oral surface and a
convex, upwardly directed and light coloured
oral surface and a convex , upwardly directed
and much darker aboral surface.
16. 6. The pentagonal mouth lies in the centre of oral surface and surrounded by
oral spines.
7. The narrow ambulacral grooves arise from the five corners of mouth and
extend through the middle of each arm upto the tip.
8. Each ambulacral groove bears four rows (two double rows ) of soft thin
walled tubular retractile tube – feet with sucker – like extremities.
17. OPHIOTHRIX
General Characters :-
1. It is commonly known as ‘ spiny brittles
star’.
2. Brilliantly coloured with phosphorocence.
3. The body is divisible into a small rounded
central disc and five greatly developed
fragile and flexible arms sharply marked
off from the disc.
4. The arms are covered by plates or shields
fringed with spines on all sides.
5. The mouth is on the oral surface and is
with five movable plates serving as jaws.
18. 6. Only the madreporite is present near the mouth on the oral surface.
7. The oral surface also bears five shields and podial pores.
8. Ambulacral grooves and pedicellariae are absent.
9. The tube feet without suckers are present on the lower plates of arms.
10. When distributed it readily breaks of one or more arms , which are
later regenerated.
11. The anus is absent.
12. The sexes are separate.
13. The development is indirect with pelagic ophiopluteus larva.
14. The genital bursac are present at the base of each arm.
15. They have great power of regeneration or autotomy.
19. ECHINUS
General Characters :-
1. It is commonly known as ‘sea urchin.’
2. The hared and prickly body is globular
in shape, slightly pentagonal in
equatorial outline with rounded
angles .
3. The body is more or less flattened at
the two poles, forming distinct oral .
4. The colour of the body may be brown,
black , purple, green, white or red.
5. The body is enclosed in a shell or
corons formed of closely fitting firmly
united calcaeous plates.
20. 6. Body surface is covered by numerous cylindrical , solid , spines.
7. Among spines are found stalked pedicellarise with three jaws and tube feet
arranged in five double rows.
8. The more flattened oral surface bear rounded central mouth surrounded by
thin, soft flexible peristome.
9. Through mouth project ten hard , white calcareous teeth from Aristotle’s
lantern.
10. At the outer edge of peristome lie ten little boshy, thin walled and branching
gills one pair opposite to each inter ambulacral area.
11. The aboral, end is somewhat dome-shaped and lie opposite to oral end.
12. At the aboral end lies a much smaller aperture , the anus , surrounded by
periproct.
13. The sexes are separate and there is no sexual dimorphism.
14. Fertilization is external.
21. HOLOTHURIA
General Characters :-
1. It is commonly known as ‘ cucumber’.
2. Body is large , cylindrical , elongated ,
vermiform and bilaterally symmetrical
with mouth and anus at opposite
ends.
3. The colour of the animal is brown or
yellowish and often reddish blue.
4. The animal rests on ground with its
long axis parallel to the surface.
5. The anus is placed at the extreme
aboral end.
22. 6. The retractile and locomotory podia are distributed all over the body
7. The surface of the animal is divided into five ambulacral and five
interambulacral zones which are not recognizable externally.
8. Body wall leathery and muscular with exoskeleton in the form of calcareous
ossicles.
9. The mouth is at the oral end and is surrounded by peristome and 20 or 30
pellate tentacles.
10. The respiratory tree is well developed .
11. The Cuvierian organ present.
12. Water vascular system is well developed.
13. The madreporite is internal.
14. The sexes are separate
15. The development is indirect with curricular larva.
23. CUCUMARIA
General Characters :-
1. It is commonly known as ‘ sea
cucumber’.
2. Body is elongated and cylindrical with
terminal mouth and anus opening at
opposite ends.
3. The anterior oral end is somewhat
thicker that the posterior aboral end.
4. The oral and aboral axis greatly
elongated.
5. Body is pentamerous , having five
longitudinal bands or ambulacra, each
is provided with double row of
locomotary podia.
24. 6. Three of these ambulacral areas are ventral and provided with numerous
tube feet with suckers.
7. The other ambulacral are dorsal and are with smaller tube feet lacking
sucker.
8. Mouth is surrounded by a lip thin, darkly pigmented peristomial
membrane and a circlet of ten dendritic , tree-like tentacles , two belonging
to each ambulacrum.
9. Each tentacle is enlarged, specially modified tube – feet of highly
sensitive and contractile nature.
10. The smooth , thin and collar like body at the base of tentacles is known
as introvert.
11. Two respiratory trees are present.
12. Water vascular system is well developed.
