The Echinoderms Phylum Echinodermata

Echinoderms Marine Sea stars Brittle stars Sea urchins Sea cucumbers Sea lilies

Brittle Star

Sea Urchin

Aristotle’s Lantern – chewing mechanism attached to teeth - circular

Sea Cucumber

Sea Lily

Found in all oceans/at all depths Most common animal in extreme depths 11,000 m – Philippine Trench

No parasitic/mostly symbiotic Many other animals live on and in echinoderms Algae/protozoa/ctenophores/snails/clams fish etc. Particle feeders/predators Scavengers/browsers/deposit or filter feeders

Very unusual group of animals Confusing to scientist even today Name is derived from their external spines 2 Sub phyla/6 classes Fossil record dates back to the Cambrian period

Subphylum Pelmatozoa Stalk animal Connected to a substrate Class Crinoidea – lily form Sea lilies Feather stars

Subphylum Eleutherozoa Free animal – not bound Class Concentricycloidea- sea daisies – center form Asteroidea- sea stars ( star fish) – star form

Ophiuroidea- brittle stars – snake form Echinoidea- sea urchins – hedgehog form Holothuroidea- sea cucumbers – sea cucumber from

Unusual Characteristics Free moving – Radial Symmetry Mirror image more than 1 plane Bilateral larva- Radial Adults – results in 90% reorientation of body axis Very complex internal – Radial symmetry Coelom has been transformed into a water vascular system (system of tubes and ducts) that uses hydraulic power

Hydraulic power is used to operate tube feet – small muscular fluid filled tubes Food gathering/locomotion Endoskeleton of dermal ossicles – can fuse together to form plate of armor Ambulacral area –mouth to tip of each arm Miniature jawlike pinsers(pedicellariae) can have poison glands(little foot)

Echinoderms Echinoderms/chordates have common ancestor Evolutionary history very unknown/has made them different from any other animal Deuterostome -pattern of development – anus forms first – they have this in common with vertebrates Protostome – all other invertebrates – mouth forms first

Characteristics Nonmetameric body Radial symmetry 5 or more radiating areas No cephalization – no head or brain Tactile/photo/chemo statysts Nervous system has circumforal ring and radial nerves 2 or 3 systems of rings at different levels Complete digestive system – usually coiled

characteristics Madreporite or sieve plate takes water in to water vascular system Respiration – dermal branchiae, tube feet, respiratory tree Excretory organs absent Cannot osmoregulate No brackish water capabilities

Reproduction Sexes usually separate Some hermaphroditic Multiple gonads Ducts release gametes Fertilization is usually external Egg develops into free swimming larva Bilateral symmetry

Regeneration Sea stars can regenerate lost limbs Can take months to regenerate Also possess autonomy- can self amputate injured piece of arm or part Some species can regenerate a new sea star from a lost arm if it contains part of the central disc