Echinoderms & Chordates

Echinoderms &Chordates

Phylum Echinodermata (echinoderms) • About 6,000 species • All _______________

Phylum Echinodermata (echinoderms) • Eucoelomates, triploblastic

Phylum Echinodermata (echinoderms) • Eucoelomates, triploblastic • Pentamerous (5-part) radial symmetry as adults • Parts arranged around oral/aboral axis

Phylum Echinodermata (echinoderms) • Why not in ___________? Larva bilaterally symmetrical!

Phylum Echinodermata (echinoderms) • 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

Phylum Echinodermata (echinoderms) • Complete digestive system • Reproduction: have good regeneration abilities, some can break into parts and reproduce asexually.

Phylum Echinodermata (echinoderms) • 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)

Phylum Echinodermata (echinoderms) • Deuterostomes

Phylum Echinodermata (echinoderms) • 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)

Phylum Echinodermata (echinoderms) • 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

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

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

Phylum Echinodermata (echinoderms) • Class Asteroidea (sea stars) • The rest of the story: part of problem may be overcollecting of tritons, a gastropod that preys on these starfish

Phylum Echinodermata (echinoderms) • 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.

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

Phylum Echinodermata (echinoderms) • Class Echinoidea (sea urchins/sand dollars) • Pedicillariae. Discourage small invertebrates from settling on surface.

Phylum Echinodermata (echinoderms) • 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)

Phylum Echinodermata • Class Holothuroidea (sea cucumbers) • Symbiosis story: black pearlfish can be found living in _________ of sea cucumbers

Phylum Echinodermata • Class Holothuroidea (sea cucumbers) • Sea cucumber defense tactic: regurgitate internal organs and _____________ them later

Phylum Echinodermata (echinoderms) • 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.

Echinoderms & Chordates