1. COLLAGE OF NATURAL AND
COMPUTATIONAL SCIENCE
DEPARTMENT OF BIOLOGY
ZOOLOGICAL SCIENCE POST GRADUATE
PROGRAM
ADVANCED INVERTEBRATE
ZOOLOGY(BIOL.6022)
ASSIGNMENT ON: PHYLUM
ECHINODERMATA
2. PHYLEM ECHINODERMATA
1. INTRODUCTION
An echinoderm is a marine invertebrate of the
phylum Echinodermata.
Echinoderms are most beautiful
They are colorful organisms with unique
shapes.
Echinodermata means “spiny skin”
3. Cont.…
They have a pentamerous radial symmetry
multicellular organisms with well-developed organ
systems.
The water vascular system present for gaseous
exchange, circulation of nutrients and waste
elimination.
4. General Characteristics
1. They have a star-like appearance and are spherical
or elongated.
2. They are exclusively marine animals.
3. The organisms are spiny-skinned.
4. They exhibit Organ-system grade of body
organization.
5. They are triploblastic, coelomate and radially
symmetrical animals
6. Body unsegmented
5. Cont....
7. Head absent;
8. endoskeleton of dermal calcareous ossicles with
spines,
9. water-vascular system of coelomic origin, including
podia or tube feet for locomotion and usually with a
madreporite.
6. Cont...
10. Coelom of enterocoelous type constitute the
perivisceral cavity and cavity of the water vascular
system.
11. Alimentary canal straight or coiled.
12. Vascular system and haemal system, enclosed in
coelomic perihaemal channels.
7. Cont...
13. Respiratory organs include dermal branchiae,
tube feet, respiratory tree and bursae. opedoped
sense organs include tactile organs, chemoreceptors,
terminal tentacles, photoreceptors and statocysts.
16. No excretory organs.
17. Usually dioecious, and fertilization is external.
18. Development indirect through free-swimming
larval forms.
8. Taxonomy and Evolution
The name echinoderm is from Ancient Greek ekhînos'
spiny, and dérma 'skin'.
Echinoderms are bilaterian symmetry
deuterostome division.
mbryo development, becomes the anus instead of the
mouth.
9. Phylogeny
Historically, taxonomists believed that the
Ophiuroidea were sister to the Asteroidea, or that
they were sister to the (Holothuroidea + Echinoidea).
However, a 2014 analysis of 219 genes from all classes
of echinoderms revised the phylogenetic tree. An
independent analysis in 2015 of RNA transcriptomes
from 23 species across all classes of echinoderms gave
the same tree.
10. Diversity
There are about 7,000 extant species .
about 13,000 extinct species.
All echinoderms are marine,
but they are found in habitats ranging from shallow
intertidal areas to abyssal depths.
11. Fossil history
The oldest candidate echinoderm fossil is Arkarua
from the Precambrian of Australia.
the fossils have no stereom or internal structure
indicating a water vascular system,
they cannot be conclusively identified.
12. Anatomy and Physiology
evolved from animals with bilateral symmetry.
adult echinoderms possess pentaradial
symmetry,
their larvae are ciliated, free-swimming
organisms with bilateral symmetry.
13. Cont.……
Echinoderms have secondary radial symmetry
adaptation to a sessile or slow-moving
existence.
Many crinoids and some seastars are symmetrical in
multiples of the basic five; starfish such as
Labidiaster annulatus possess up to fifty arms, while
the sea-lily Comaster schlegelii has two hundred.
14. Skin and skeleton
Echinoderms have a mesodermal skeleton in the
dermis, composed of ossicles.
If solid, these would form a heavy skeleton, so
They have a sponge-like porous structure known
as stereom.
Ossicles may be fused together, as in the test of
sea urchins,
15. The water vascular system
Echinoderms possess a unique water vascular
system,
function in gas exchange, feeding, sensory
reception and locomotion.
This system varies between different classes
of echinoderm
