Echinoderms Flashcards
Main features
Marine
Deuterostome development
Pentaradial symmetry
Calcareous endoskeleton (ossicles)
Water vascular system - tube feet
Complete gut
Decentralised nervous system
Reproduction
Spawning - fertilised eggs develop into planktonic free swimming larvae - arm structures to stop sinking
Stelleroidia
Asteroidia/Ophiurodia
Asteroidia
5 arms - can have up to 40
Starfish + sea stars
aboral surface - anus in middle
Oral surface has mouth - walking grooves
Tube feet can be retracted using vascular system
Ossicles - rigid + protection
Ophiuroidea
Brittle stars
5 arms
Developed ossicles (vertebral ossicle joints)
Very mobile
Tube feet for sensory - no loco
Holothurians
Sea cucumbers
Pentaradial symmetry - tentacle end
Small ossicles
Echinoidea
Sea urchins/heart urchins/ sand dollar
Radial + pentaradial symmetry
Ossicles form plates - hard armour
Holes for feet
Spines made from calcite
Mobile - socket joints
Poison sac - tip of spines
Pedicellaria
Claw like modified spines - protect from settling organisms
Nipping + cutting types
Water vascular system
System of fluid filled tubes
Water enters and leaves in madreporite
Ring canal around mouth
Radial canals down arms
Lateral canals off radial
Connect to podia (locomotion)
Podia muscles contract to shorten the podium - water forced back into ampulla
Prey items
bivalves/snails/crustaceans/coral
Feeding in asteroids
mouth leads to pyloric stomach
Pyloric caecae - run down each arm - enzymes for digestion
Feeding in Echinoids
Coiled intestine
Mouth has 5 teeth that can be extended/retracted/moved from side to side - Aristotle’s lantern
Grow continuously
Regeneration
Can cast of arms as decoys and regenerate
Linckia - Can regenerate an entire animal from 1 arm
Mutable connective tissue (can be made rigid or flexible) - very chepa in terms of E use
