Phylum Echinodermata “Spine skin” Marine (or estuarine) Water vascular system Pentaradial symmetry

Echinodermata 6500 species living 13,000 from fossils Classes: Crinoidea, Stelleroidea, Echinoidea, Holothuroidea

Water vascular system Fluid-filled canals that lead to tube feet Sea star: madreporite, stone canal, ring canal, radial canal, ampulla, tube feet

Water vascular system Tiedemann’s body: Contains phagocytes; remove foreign matter such as bacteria from incoming seawater

Water vascular system Ambulacral ossicles support ampullae and tube feet Contraction of ampulla moves fluid to tube feet Muscles in tube feet for retracting HPhAGyDceLo

Water vascular system Cilia on inner surface of tube feet circulate water Gas exchange Fluid similar to seawater; contains coelomocytes, proteins, K ions

Class Crinoidea Lily-like Feather stars and sea lilies Oldest of living echinoderms

Class Crinoidea Feeding, repro structures at top of stalk Complete digestive system in calyx: mouth – intestine, anus ch?v=s1xfRc4SDsw

Class Crinoidea Arms have ambulacral groove with mucus- secreting glands adjacent. Food particles stick in mucus, flicked to the ambulacral groove, then mouth

Class Stelleroidea Armed echinoderms Brittle stars, sea stars

Brittle stars and basket stars ~ 2100 described Joints allow flexibility Tube feet present Sensitive to light – oral surface mj8ZYysrmxU

Brittle stars and basket stars Tube feet through small holes Digestive system mostly in disc – no anus Bursal slits for water exchange

Deposit feeders, suspension feeders, carnivores, scavengers Many are nocturnal Many live in associations Brittle stars and basket stars

Sea stars ~ 1600 species Arms not as distinct from disc as in brittle stars Move slowly with tube feet Tube feet move individually

Figure 20_06

Sea stars Digestion: lower cardiac stomach digests food Upper pyloric stomach for secreting enzymes and absorption

Pedicellariae: stalked or sessile

Figure 20_09

Concentricycloids – sea daisies Recently (1986) discovered echinoderms > 1000 m New Zealand, Bahamas –Tube feet arrangement different

Class Echinoidea: spine-like Sea urchins, sand dollars < 1000 species

Class Echinoidea: spine-like Ossicles form test Complex system of ossicles and muscles for grazing = Aristotle’s lantern

Spines attach to skeleton – ball and socket joint Toxins Ossicles flat and joined = inflexible

Class Echinoidea: spine-like Tube feet in 5 double rows of plate Pedicellariae – globular forms have toxin

Feeding and digestion: Aristotle’s lantern Teeth protruded to scrape algae or consume food Species w/o lantern usually detritivores

Mouth – esophagus – intestine – anus WVS m/watch?v=D3W4OCn HyCs

Class Holothuroidea: sea cucumbers ~ 1200 species

Ossicles microscopic Multiple shapes

Tube feet modified into tentacles around mouth Mostly deposit-feeders, few filter-feeders

Digestion system: elongated Mouth – esophagus – stomach – intestine – cloaca – anus WVS – madreporite in coelomic cavity = no outside connection

Respiratory tree: connects to cloaca – water supply Expulsion of internal organs

Echinoderm repro + development: Some are asexual Most are dioecious Multiple gonads, gametes into seawater = external fert

Distinctive ciliated larval form in each class Free-swimming, planktonic Metamorphosis into adult

Echinoderm NS No brain 3 nerve networks Ectoneural = ring around esophagus: receives sensory input

Echinoderm NS Hyponeural = circumoral nerve: motor function Entoneural = associated with aboral end, neurons from stalk down arms