the 5 classes asteroidea (sea stars), ophiuroidea (brittle stars), echinoidea (sea urchins and sand...

The 5 Classes

• Asteroidea (sea stars),

• Ophiuroidea (brittle stars),

• Echinoidea (sea urchins and sand dollars),

• Crinoidea (sea lilies or feather stars),

• Holothuroidea (sea cucumbers).

Phylum Echinodermata

• pentamerous radial symmetry as Adults

• Endoskeleton (plates or spicules)

• water vascular system

• Includes Sea Stars, Brittle Stars, Sea Urchins and Sand Dollars

BODY ADVANCE

PHYLUM ECHINODERMATA (means spiny skin)

ex: starfish, sea urchins, sand dollars

Why are they considered advanced?

1. endoskeleton of calcium carbonate plates

2. bilaterally symmetrical larvae

3. water vascular system instead of muscles is a big advantage in predatory situations

4. highly regenerative - can eviscerate

5. Dimorphic -separate sexes; external fertilization6. Sexual Reproduction

Why are they considered simple?

1. Light-sensitive eyes located at the end of each ray do not provide vision because there is no brain nor head. – They lack cephalization

2. They have reduced internal organs - no respiratory, circulatory, excretory nor nervous system.

3. Adults have pentamerous (5) radial symmetry .

4. Respiration is by diffusion through the skin.

Starfish are scavengers and eat a variety of organisms.

The starfish can open a clam shell a few centimeters wide.

Then by inverting its stomach into the shell, the clam is digested and absorbed. – This is called self evisceration

Missing parts from injuries or evisceration are quickly replaced. Any portion of the central disk (ring canal) will regenerate a new starfish - a fact that oyster fishermen learned too late!

Water Vascular System

Water Vascular Animation

Which type of symmetry does the starfish have?

Bila

tera

l

Bira

dial

Pen

tam

erous

Radia

l

asy

mm

etric

al

0% 0%0%0%

1. Bilateral

2. Biradial

3. Pentamerous Radial

4. asymmetrical

What type of fertilization occurs with starfish

Ext

ernal

Sex

ual

Inte

rnal

Sex

ual

Ase

xual

Buddi

ng

0% 0%0%0%

1. External Sexual

2. Internal Sexual

3. Asexual

4. Budding

Tube Feet

STRONG ENOUGH TO PULL APART A CLAM!!!

Stomach Eversion for Eating

Class Asteroidea

Sea Stars

Class Ophiuroidea

Brittle Stars

Class EchinoideaSea Urchins

Keeled Heart Urchin

Sand Dollar

Note: Pentamerous Radial symmetry

Aristotle’s Lantern – Jaws and teeth of the Urchin. Similar structure to the Buccal mass found in which organsim?

Keeled Heart Urchin

Starfish have ____ arms

4 5 6 8

0% 0%0%

100%1. 4

2. 5

3. 6

4. 8

Echinodermata means

Spin

y Ski

n

Chin

ese

Skin

Fiv

e Arm

s

Sta

r Ski

n

55%

9%

36%

0%

1. Spiny Skin

2. Chinese Skin

3. Five Arms

4. Star Skin

Which is NOT in the Phylum Echinodermata?

San

d Dol

lar

Sea

Urc

hin

Sta

r Fis

h

Brit

tle C

rab

17%

75%

8%0%

1. Sand Dollar

2. Sea Urchin

3. Star Fish

4. Brittle Crab

Pentamerous means they are ____ sided.

2

Bila

tera

lly 5

Spin

ey

0% 0%

92%

8%

1. 2

2. Bilaterally

3. 5

4. Spiney

If a starfish arm is cut off and a portion of the _______ is also cut off with it a

new starfish will regenerate

Dig

estiv

e sy

stem

Rep

rodu

ctiv

e sy

stem

Sto

mac

h

Cen

tral C

anal

(dis

k)

0%

92%

0%8%

1. Digestive system

2. Reproductive system

3. Stomach

4. Central Canal (disk)

And Next ……

ECHINODERMATA Class Stelleroidea

• Subclass Asteroidea• Red textile sea star or

necklace sea star (Fromia monilis) from the Solomon Islands in the western Pacific

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Photo Copyright © Diane R. Nelson


• Subclass Asteroidea• Blue sea star (Linckia

laevigata) from Fiji• Common large sea

star in the Pacific




• Subclass Asteroidea• Close-up of a blue

sea star (Linckia laevigata) from the Great Barrier Reef in Australia




• Subclass Asteroidea• Luzon sea star

(Echinaster luzonicus) from the Solomon Islands

• This sea star often has six or seven arms due to regeneration




• Subclass Asteroidea• Granulated sea star

(Choriaster granulatus) from Fiji scavenges on dead organisms

• A large Pacific sea star with broad arms




• Subclass Asteroidea• Crown-of-Thorns sea

star (Acanthaster planci) from Fiji, showing the long spines and multiple arms

• Preys on live corals




• Subclass Asteroidea • Tube feet of a Crown-

of-Thorns sea star (Acanthaster planci)

• Population explosions of this sea star decimate local reefs




• Subclass Ophiuroidea• Brittle star

(Ophiomyxa sp.) crawls across a mushroom leather coral (Sarcophyton sp.) on the Great Barrier Reef of Australia




• Subclass Ophiuroidea• Sponge brittle star

(Ophiothrix suensonii) on a red erect rope sponge (Amphimedon compressa) in Belize

• Note thin glassy spines on arms




• Subclass Ophiuroidea• Giant basket star

(Astrophyton muncatum) perched in the current on a soft coral at night in Belize

• Feeds on plankton in the water column




• Subclass Ophiuroidea• Giant basket star

(Astrophyton muricatum) perched on a stony coral in the current at night in Roatan, Honduras, feeding on plankton



ECHINODERMATA Class Echinoidea

• Long-spined black urchin (Diadema antillarum) from Roatan, Honduras

• Long, thin, hollow spines are venomous

• Populations, once decimated by a blight, now recovering




• Toxic flower urchin (Toxopneustes pileolus) from the Solomon Islands

• Flower-like disks are jawed pedicellariae that can inject toxin




• Royal urchin (Mespilia globulus), from the Solomon Islands

• Found in shallow water coral rubble and on patch reefs




• Six-keyhole sand dollar (Mellita sexiesperforata) from the Bahamas, aboral surface, showing lunules (oval holes) and petaloids (center)




• Six-keyhole sand dollar (Mellita sexiesperforata) from the Bahamas

• This is the oral surface, with the mouth located in the center




• A live sea biscuit (Clypeaster sp.) from the Bahamas

• With short spines, it burrows into sand during the day, emerging occasionally at night



ECHINODERMATA Class Holothuroidea

• Graeff’s sea cucumber (Bohadschia graeffei) from the Great Barrier Reef in Australia

• Black pads are modified buccal podia for feeding in sediment




• Close-up of anterior end of Graeff’s sea cucumber (Bohadschia graeffei), with modified buccal podia (black pads) for feeding




• Unidentified sea cucumber from the Solomon Islands, releasing sperm (white stream) from a dorsal pore behind the mouth

• Buccal podia have been retracted




• Close up of dorsal pore on unidentified sea cucumber from the Solomon Islands

• White milky stream is sperm being released into the water column




• Sand feces from a sea cucumber, released from the cloacal opening



ECHINODERAMATA Class Holothuroidea

• Eyed sea cucumber (Bohadschia argus)

• Cloacal opening, with white threads, is on left; mouth is on right

• White threads are the tubules of Cuvier, which are toxic




• When disturbed, this eyed sea cucumber (Bohadschia argus) discharges its tubules of Cuvier from the cloacal opening

• These sticky, toxic threads are used for defense




• The pineapple sea cucumber (Thelenota ananas) is large with distinctive conical papillae

• Abundant in the Pacific




• Close-up of the stellate conical papillae on a pineapple sea cucumber (Thelenota ananas) in Papua New Guinea




• Sticky sea cucumber (Euapta geodeffroyi) from the western Pacific

• These sea cucumbers lack tube feet and move by contractions of the body



ECHINODERMATA Class Crinoidea

• Yellow feather star or crinoid (Comanthina schlegeli) from Fiji

• This species has about 130 arms and is active both at night and during the day




• Feather star (crinoid) perched on a stony coral in the current in Fiji

• This animal feeds on plankton in the current




• A feather star (Crinoid sp.) has used its basal cirri to “walk” to a high point on the reef to feed on plankton in the current




• Pinnate arm of a feather star (crinoid)

• Podia on the pinnules are used for gas exchange and food capture



the 5 classes asteroidea (sea stars), ophiuroidea (brittle stars), echinoidea (sea urchins and sand...

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