ECHINODERMATA
The term Echinodermata (Gr., echinos= spiny, derma=skin), was coined by Jacob
Klein. The organisms belonging to the phylum Echinodermata are exclusively marine. Till
date, there have been no traces of any terrestrial or freshwater Echinoderms.
These are multicellular organisms with well-developed organ systems. All the animals
belonging to this phylum share the same characteristics features. They are colourful organisms
with unique shapes. They are ecologically and geologically very important.
The Echinoderms are found in sea-depths as well as in the intertidal zones. An interesting
feature of the phylum Echinodermata is that all the organisms belonging to this phylum are
marine. None of the organisms is freshwater or marine.
The water vascular system present in echinoderms accounts for gaseous exchange, circulation
of nutrients and waste elimination.
Characteristics of Echinodermata
▪ Echinoderms are triploblastic, radially symmetrical (adult) often pentamerous
(star like), larva with bilateral symmetry, sessile or creeping at bottoms.
▪ Echinoderms are exclusively marine deuterostomes (the anus develops from the
first opening in the embryo and the mouth develops later).
▪ All echinoderms are benthic; bottom dwellers (except few pelagic sea
cucumbers), mostly free living except sea lilies.
▪ Spiny skinned; enterocoelic coelomate; organ system grade of organization;
gregarious
▪ Body is unsegmented
▪ Echinoderms are uncephalized (head absent), body parts organized about an oral-
aboral axis where the mouth is present on the ventral side while the anus is on
the dorsal side
▪ Endoskeleton (mesodermal origin) is composed of unique calcareous ossicle
bearing protective spines.
▪ Digestive tract is complete except Brittle star.
▪ An outstanding characteristic of echinoderms is their complex coelom
(enterocoel) and its ambulacral system, derivatives; the water vascular system,
perivisceral coelom and haemal system.
▪ Locomotion by contractile appendages of ambulacral system/ water vascular
system called tube feet.
▪ Tube feet consists of ampulla, podium and sucker. It also serves for respiration
and food capture.
▪ Presence of pinna like structure called pedicellariae that protects the skin gills.
▪ Excretory system is absent.
▪ Nervous system is diffused decentralized, usually consisting of nerve net, nerve
ring and radial nerves, but no brain.
▪ Sense organs are poorly developed and consists of tactile tentacles, pigment eye
spots and statocysts.
The term Echinodermata (Gr., echinos= spiny, derma=skin), was coined by Jacob
Klein. The organisms belonging to the phylum Echinodermata are exclusively marine. Till
date, there have been no traces of any terrestrial or freshwater Echinoderms.
These are multicellular organisms with well-developed organ systems. All the animals
belonging to this phylum share the same characteristics features. They are colourful organisms
with unique shapes. They are ecologically and geologically very important.
The Echinoderms are found in sea-depths as well as in the intertidal zones. An interesting
feature of the phylum Echinodermata is that all the organisms belonging to this phylum are
marine. None of the organisms is freshwater or marine.
The water vascular system present in echinoderms accounts for gaseous exchange, circulation
of nutrients and waste elimination.
Characteristics of Echinodermata
▪ Echinoderms are triploblastic, radially symmetrical (adult) often pentamerous
(star like), larva with bilateral symmetry, sessile or creeping at bottoms.
▪ Echinoderms are exclusively marine deuterostomes (the anus develops from the
first opening in the embryo and the mouth develops later).
▪ All echinoderms are benthic; bottom dwellers (except few pelagic sea
cucumbers), mostly free living except sea lilies.
▪ Spiny skinned; enterocoelic coelomate; organ system grade of organization;
gregarious
▪ Body is unsegmented
▪ Echinoderms are uncephalized (head absent), body parts organized about an oral-
aboral axis where the mouth is present on the ventral side while the anus is on
the dorsal side
▪ Endoskeleton (mesodermal origin) is composed of unique calcareous ossicle
bearing protective spines.
▪ Digestive tract is complete except Brittle star.
▪ An outstanding characteristic of echinoderms is their complex coelom
(enterocoel) and its ambulacral system, derivatives; the water vascular system,
perivisceral coelom and haemal system.
▪ Locomotion by contractile appendages of ambulacral system/ water vascular
system called tube feet.
▪ Tube feet consists of ampulla, podium and sucker. It also serves for respiration
and food capture.
▪ Presence of pinna like structure called pedicellariae that protects the skin gills.
▪ Excretory system is absent.
▪ Nervous system is diffused decentralized, usually consisting of nerve net, nerve
ring and radial nerves, but no brain.
▪ Sense organs are poorly developed and consists of tactile tentacles, pigment eye
spots and statocysts.
