Ch. 38 – Echinoderms Ch. 38 – Echinoderms Phylum: Echinodermata

Sea stars, sand dollars, brittle stars, & sea cucumbersMarine Usually 5 arms pentaradialNo circulatory, respiratory, or excretory systemsWater-vascular systemTube feet that aid in movement

VideoVideo

Most invertebrates have an exoskeleton to support them . Echinoderms have an endoskeleton, which is a skeleton within the body.

This is why echinoderms are thought to be closer related to vertebrates.

5 Classes of Echinoderms 5 Classes of Echinoderms 1. Ophiuroidea brittle stars & basket

stars2. Crinoidea sea lilies & feather

stars3. Holothuroidea sea cucumbers4. Echinoidea sand dollars & sea

urchins5. Asteroidea starfish & sea stars

Class: OphiuroideaClass: OphiuroideaBrittle starsGets it name brittle because its has

long, thin arms and are constantly breaking off and regenerating.

Pg 783

Class: CrinoideaClass: Crinoidea

Sea lilies & feather starsSessilePg. 782

Class: HolothuroideaClass: HolothuroideaSea cucumberSoft bodyIf threatened the sea cucumber may eject

their organs out of their body at the predator – called eviscerate. They then regenerate their organs.

Video- http://www.youtube.com/watch?v=aCxKFc3XtJs

Pg. 784

Class: EchinoideaClass: EchinoideaSand dollars & sea urchinsThey have an Aristotle’s lantern,

which is a jaw-like structure for grinding their food.

Sea urchins have long spines with sometimes venom for protection

Sand dollars are about the size of a silver dollar.

Class: Asteroidea (sea star)Class: Asteroidea (sea star)

Body Structure (external)Aboral surface Madreporite is located

(top side)Oral surface mouth is located (bottom

side)Ossicles calcium spinesPedicellarie tiny little pinchers that clean

the body surface so debris doesn’t collect.Video

Water- Vascular SystemWater- Vascular SystemUsed to create movementEnters the madreporite stone

canal ring canal 5 radial canals lateral canal the tube feet (100s of tube feet), have ampulla (air sacs), that act like a pipette and release the water with pressure. Pg. 786

Body SystemsBody SystemsNo circulatory, respiratory, or excretory

systems.Each arm has an eyespot at the end,

which senses light and touch.Digestion They have digestive

glands. Their tube feet are strong enough to open clams & mussels.

Reproduction Each arm of the sea star has 2 gonads that produce eggs and sperm cells. They are hermaphrodites.

Sea stars can regenerate lost parts. A new sea star can regenerate from a segment of an arm as long as it has part of the ring canal attached.