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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 animal – not bound Class Concentricycloidea- sea daisies – center form Asteroidea- sea stars ( star fish) – star form Free brittle stars – snake form Echinoidea- sea urchins – hedgehog form Holothuroidea- sea cucumbers – sea cucumber from Ophiuroidea- Unusual Characteristics 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 Free 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 – dermal branchiae, tube feet, respiratory tree Excretory organs absent Cannot osmoregulate No brackish water capabilities Respiration 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