Echinoderms & Chordates

Echinoderms &Chordates

Phylum Echinodermata (echinoderms)

• About 6,000 species

• All _______________


• Eucoelomates, triploblastic


• Eucoelomates, triploblastic

• Pentamerous (5-part) radial symmetry as adults

• Parts arranged around oral/aboral axis


• Why not in ___________? Larva bilaterally symmetrical!


• Calcareous endoskeleton. Plates form surrounded by tissues.

• Arises from mesoderm. “echino-” means spiny, “-derm” means skin.

Phylum Echinodermata• Water vascular system in _____________• Connect to tube feet• Note madreporite on aboral surface of starfish

(takes water into system)

Phylum Echinodermata• Tube feet in action

QuickTime™ and aCinepak decompressorare needed to see this picture.


• Complete digestive system • Reproduction: have good regeneration

abilities, some can break into parts and reproduce asexually.


• Most reproduce sexually• Dioecious, fertilization external

Phylum Echinodermata• No head or well developed brain (nerve ring)• No excretory organs (no flame cells, nephridia,

etc.)• No respiratory system (tube feet and papulae

help exchange gases)


• Deuterostomes


• Class Crinoidea (sea lilies/feather stars)• Class Asteroidea (sea stars)• Class Ophiuroidea (brittle stars)• Class Echinoidea (sand dollars and sea urchins)• Class Holothuroidea (sea cucumbers)


• Class Crinoidea (sea lilies/feather stars)– Sessile for some or all of life. Add new __________ as

they grow.– Have mouth and anus on upper surface.

Phylum Echinodermata• Class Crinoidea (sea lilies/feather stars)

– Glorious fossil past (6000 fossil species, 600 living ones).

Wisconsin




• Class Asteroidea (sea stars)– 1500 species. Active and important marine predators– Move about on tube feet


• Class Asteroidea (sea stars)– Predation may cause problems– Ex, crown of thorns starfish (coral predator)


• Class Asteroidea (sea stars)– The rest of the story: part of

problem may be overcollecting of tritons, a gastropod that preys on these starfish




• Class Ophiuroidea (brittle stars)– 2000 species. Abundant, nocturnal. Move using

two arms at a time– Feed on plankton and organic debris with tube

feet.



Phylum Echinodermata• Class Echinoidea (sea urchins/sand dollars)

– Lack arms. 1000 species. Endoskeleton of fused calcareous plates

– No arms or rays. Have rows of spines and tube feet. Spines and feet moveable.


• Class Echinoidea (sea urchins/sand dollars)– Sea urchins: long spines– Sand dollars: short spines


• Class Echinoidea (sea urchins/sand dollars)– Pedicillariae. Discourage small invertebrates

from settling on surface.


• Class Echinoidea (sea urchins/sand dollars)– Aristotle’s lantern: complex chewing apparatus.

Phylum Echinodermata• Can be important members of marine

ecosystems• Ex, sea urchins as herbivores

Urchins, sea otters, and kelps• Sea otters hunted

almost to extinction on West Coast

• Now expanding back

• Top carnivores (almost): eat mussels, abalone, sea urchins.

Purple sea urchin

Urchins, sea otters, and kelps

• Urchins eat __________ of kelp

• Fewer urchins now that otters are back.

Urchins, sea otters, and kelps• Giant kelp forests

recovering as otters return.• Fish and other associates

rebounding.

Sea urchins• Eggs (roe) edible, delicacy (known as uni in sushi bars)



Phylum Echinodermata• Class Holothuroidea (sea cucumbers)

– Elongate– Soft bodied (endoskeleton plates reduced or

absent)– Often with feeding tentacles around mouth

Phylum Echinodermata• Class Holothuroidea (sea

cucumbers)– Have respiratory organ (respiratory

tree) (11, F), arising from cloaca (12, G: near anus, 13)

– Gonads (8, H)– Intestine (10, I)


– Symbiosis story: black pearlfish can be found living in _________ of sea cucumbers


– Sea cucumber defense tactic: regurgitate internal organs and _____________ them later


• Class Holothuroidea (sea cucumbers)– Edible: braised sea cucumber with tea leaves

Phylum Chordata (chordates)• About 43,000 species

• Triploblastic, eucoelomates

Phylum Chordata (chordates)• Bilateral symmetry • Deuterostomes

Segmentation• Present in chordates• Often visible in embryo

Internal skeleton• Differs from echinoderms. Rodlike, deeper

in body. Gives attachment points for muscles.

Human skeleton

4 Key Features• 1) Hollow (tubular!) nerve cord

under *dorsal* surface

4 Key Features• 1) Hollow (tubular!) nerve

cord under *dorsal* surface• Becomes brain and spinal cord• *Invertebrates usually have

ventral nerve cords.

4 Key Features• 2) Notochord: flexible rod just under nerve

cord. Originally served as muscle attachment point

4 Key Features• 3) Pharyngeal pouches in embryo• In humans, only one remains to form

Eustachian tubes connecting inner ear to __________.

4 Key Features• 4) Postanal tail (at least during embryonic

stages). Nearly all other animals with terminal anus

Chordate survey• Subphylum Urochordata (tunicates)• Subphylum Cephalochordata (lancelets)• Subphylum Vertebrata (vertebrates)

Chordate survey• Subphylum Urochordata (tunicates)

– Marine. 1300 species.

Chordate survey• Subphylum Urochordata (tunicates)

– Adult sessile, filter feeder. – Has holdfast, siphons (incurrent & excurrent,

pharynx). Cilia in pharynx create water current.

Chordate survey• Subphylum Urochordata

(tunicates)– Pharynx used to feed,

traps food in mucus on endostyle

– Pharynx has gill slits for breathing

– Many adults secrete tunic: tough sac of ______________ around body.


Chordate survey• Subphylum Cephalochordata (lancelets)

– Marine. 20 species.– Ex, Amphioxus or Branchiostoma


– Filter feeder, can swim– Oral hood has tentacles (sensory)– Cilia create water current, used for breathing and filter

feeding. Water exits via _________________.


– No head, brain, eyes, etc.– Skin only 1 cell layer thick (vertebrates with multi-

layered skin)– ________________: segmented muscles.


– Model version (as seen in lab)


Subphylum Vertebrata (vertebrates)

• Distinctive features– 1) Have vertebral

column. Bony segments replace __________, enclose spinal cord


• Distinctive features– 2) Have well-developed head (with skull and

brain)


• Other features– 3) Neural crest in embryo. Cells migrate to

form many tissues (parts of muscle, nerve, skin, systems, etc.) in various places in body.


• Other features– 4) Internal organs: liver, kidneys, endocrine

glands, heart and closed circulatory system– 5) Endoskeleton of _________ (protein) or bone

(protein and calcium crystals). Bone strong but not brittle. Can make big bodies this way.

Chordate survey• Subphylum Vertebrata (vertebrates)

– Class Agnatha– Class Chondrichthyes– Class Osteichthyes– Class Amphibia– Class Reptilia– Class Aves– Class Mammalia

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Echinoderms & Chordates