Phylum – Echinodermata
The term Echinodermata means spiny skin given by Jacob Klein.
Leuckart raised the group a separate phylum.
Phylum Echinodermata contains some 6000 known species and constitutes the only major group of deuterostome
invertebrates.
• These animals have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata (Spiny
bodied). All are marine with organ-system level of organisation.
• The adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical.
• They are triploblastic and coelomate animals.
• Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal)
side.
• The most distinctive feature of echinoderms is the presence of water vascular system which helps in
locomotion, capture and transport of food and respiration.
• An excretory system is absent.
• Sexes are separate. Reproduction is sexual.
• Fertilisation is usually external.
• Development is indirect with free-swimming larva.
• Coelom of enterocoelous type constitutes the perivisceral cavity and cavity of the water vascular
system, coelomic fluid with coelomocytes
• Alimentary canal straight or coiled, vascular system and haemal system enclosed in coelomic
perihaemal channels
• General respiratory organ is tube foot.
• Skin gills or dermal branchiae in Starfish (Astropecten)
• Periostomial gills in Sea urchin (Echinus)
• Genital bursae in Brittle star (Ophiothrix)
• Cloacal respiratory tree in Sea cucumber (Cucumaria)
• No excretory organs. Amoebocytes help in removal of metabolicwaste.
• Nervous system without a brain and with a circumoral ring and radial nerves
• Poorly developed sense organs include tactile organs, chemoreceptors, terminal tentacles, photoreceptors and
statocysts.
• Usually dioecious, gonads large and single, fertilization external, development indirect through free swimming
larvalforms
• Regeneration of lost parts (autotomy).
• Comets : Specimens with small regenerating arms at the base of large original arm are popularly called
comets.
Examples:
• Asterias (Star fish),
• Echinus (Sea urchin),
• Antedon (Sea lily),
• Cucumaria (Sea cucumber)
• Ophiura (Brittle star).
The term Echinodermata means spiny skin given by Jacob Klein.
Leuckart raised the group a separate phylum.
Phylum Echinodermata contains some 6000 known species and constitutes the only major group of deuterostome
invertebrates.
• These animals have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata (Spiny
bodied). All are marine with organ-system level of organisation.
• The adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical.
• They are triploblastic and coelomate animals.
• Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal)
side.
• The most distinctive feature of echinoderms is the presence of water vascular system which helps in
locomotion, capture and transport of food and respiration.
• An excretory system is absent.
• Sexes are separate. Reproduction is sexual.
• Fertilisation is usually external.
• Development is indirect with free-swimming larva.
• Coelom of enterocoelous type constitutes the perivisceral cavity and cavity of the water vascular
system, coelomic fluid with coelomocytes
• Alimentary canal straight or coiled, vascular system and haemal system enclosed in coelomic
perihaemal channels
• General respiratory organ is tube foot.
• Skin gills or dermal branchiae in Starfish (Astropecten)
• Periostomial gills in Sea urchin (Echinus)
• Genital bursae in Brittle star (Ophiothrix)
• Cloacal respiratory tree in Sea cucumber (Cucumaria)
• No excretory organs. Amoebocytes help in removal of metabolicwaste.
• Nervous system without a brain and with a circumoral ring and radial nerves
• Poorly developed sense organs include tactile organs, chemoreceptors, terminal tentacles, photoreceptors and
statocysts.
• Usually dioecious, gonads large and single, fertilization external, development indirect through free swimming
larvalforms
• Regeneration of lost parts (autotomy).
• Comets : Specimens with small regenerating arms at the base of large original arm are popularly called
comets.
Examples:
• Asterias (Star fish),
• Echinus (Sea urchin),
• Antedon (Sea lily),
• Cucumaria (Sea cucumber)
• Ophiura (Brittle star).
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