Zoology 31 March 2008 Winslow
Phylum Echinodermata Hickman et al.
Deuterostomes--echinoderms, hemichordates, chordates
Phylum Echinodermata
Deuterostome, enterocoelous, radial indeterminate cleavage
Digestive system usually complete, extensive coelom
Dermal endoskeleton of spiny plates & ossicles (Ca) or spicules (Ca)
Water vascular system in coelomic compartment
Podia (tube feet), madreporite
Locomotion by podia, spines, or arms
Hemal system reduced, surrounded by coelomic compartment
Respiration by dermal branchiae, tube feet, or other means
Pedicellariae with pincers, ligaments, no excretory organs
Ambulacra, no head, circumoral ring & radial nerves
Usually separate sexes, external fertilization
Free-swimming, bilateral larvae, autotomy & regeneration
Metamorphosis to secondary radial pentamerous symmetry
Class Asteroidea--sea stars
Intertidal, reef, bottoms, many predatory
Arms & central disk, mouth, anus, oral & aboral aspects
Ambulacral grooves & tube feet (podia), suckers, protective spines
Water vascular system
Madreporite, ring canal, radial & lateral canals, ampullae
Locomotion (muscles in podia & hydrostatic pressure)
Catch collagen allows movement when liquid
Feeding & digestive system
Mouth, cardiac & pyloric stomachs
Digestive ceca, intestine, anus
Pulls shells of bivalves apart, everts stomach into shell
Respiration & excretion of N by papulae (dermal branchiae) & podia
3 nerve rings connected by nerve net, radial nerves, ocelli
Usually dioecious, gonads in each arm, external fertilization
Regeneration & autotomy, asexual fission
Free-swimming bilateral larvae (bipinnaria & brachiolaria)
Temporary stalk for metamorphosis into adult
Class Ophiuroidea--brittle stars
Largest group of echinoderms, benthic
5 slender arms
Class Echinoidea--sea urchins & sand dollars
Long spines, Aristotle's lantern w/ teeth for chewing, pluteus larva
Class Holothuroidea--sea cucumbers
Lengthened along oral/aboral axis, secondarily bilateral
Class Crinoidea--sea lilies
Extant species benthic, fossils where oceans once were
Often sessile, stalk & calyx