Echinodermata classes

Class Astroidea

Sea stars

What kind of anatomy do sea stars have?

5 thick arms extending from central body

How do sea stars acquire food?

either

“suck” food into their stomach

evert stomach and begin digestion externally

Sea stars get food by being

predators/ scavengers

How do sea stars walk?

tube feet

What do the glands in sea stars do?

excrete carbohydrates and proteins

In which way do sea stars move?

in a directed way… one arm becomes leading arm, other arms cooperate in that direction

How is arm cooperation coordinated in sea stars?

thru the nerve ring

What do sea stars have at the end of each arm?

light sensing eye spot

Class Ophiuroidea

brittle sea stars

What kind of anatomy do brittle stars have?

five long, thin arms extending from central body

Is it true that brittle stars have a harder endoskeleton compared to sea stars?

yes

What are brittle star arms like?

their ossicles are hinged, giving greater flexibility of arms

brittle stars get food by being

predators

How do brittle stars acquire food?

food is grabbed by arms—helped by mucus excreted from tube feet (NO AMPULLAE)

arms move food to mouth

Do brittle stars have ampullae?

NO

How do brittle stars walk/swim?

one leading arm, two arms on each side to sweep back and forth.

JERKY movements

What are components of brittle star arms?

they have spine projections made of ossicles

have nerve ganglia along each arm

The spine projections made of occicles allow brittle stars to?

create traction

what do the nerve ganglia along each arm in brittle stars allow?

better coordination btwn arms

brittle stars have what sensing cells?

light intensity sensing cells

What do the light intensity sensing cells allow?

allows animal to sense light/shadows from a specific direction

Do brittle stars move quickly?

yes, so they need a more complex sensory system

Class echinoidea

sea urchins and sand dollars

unique features of class Echinodea

have no arms

have spherical shape with tube feet

Regular echinoids

sea urchins

irregular echinoids

sand dollars

shape of the species in class echinoidea

flattened spherical shape

What is a “test”?

fixed lattice of ossicles that form a fused body

A test is covered in

spines

Who has sharp spines?

sea urchins

who has soft spines?

sand dollars

who is a browsing herbivore?

the sea urchin

How do sea urchins move?

slowly

How do sea urchins acquire food?

scrape seaweed from rocks using movable ossicles called “Aristotle’s Latern”

What is the aristotle’s lantern composed of?

5 jaws and 1 “tooth” in each jaw, connected by ligaments

who is a burrowing deposit feeder?

sand dollar

What do sand dollars have that sea urchins don’t?

tube feet modified for burrowing

What is the replacement for arms (Echinodea)?

five ambulacral grooves where tube feet are located

What do they use tube feet for?

walking but water vascular system isn’t as important to them

why isn’t the water vascular system not as important in class Echinoidea?

rigid test water is always retained in animal

Class Crinoidea

sea feathers and sea lillies

The most ancient class of Echinodermata?

Crinoidea

What class are filter feeders, like their ancestors?

CRINOIDEA

How do their mouths face?

upward

are they mobile?

mostly sessile

Who is entirely sessile?

sea lillies

what are sea lillies connected to?

a substrate via stalk

What are sea lily arms like?

their arms have increased surface area via feather-like modifications

Sea lily tube feet

collect food and carry it into mouth

who can switch btwn being sessile and motile?

sea feathers

Sea feather arms

have increased surface area via feather-like modifications

sea feather tube feet

collect food and carry it into mouth

How do sea feathers swim?

by waving their arms up and down

Class holothuroidea

sea cucumbers

unique characteristic of class holothuroidea

exhibits secondary bilateral symmetry as adults

What is the catch with their unique characteritic?

even tho they exhibit secondary bilateral symmetry, they are RADIALLY SYMMETRIC

What is their endoskeleton like?

it is very reduced with only few internal ossicles

do they have external spines?

no

sea cucumber tube feet

their tube feet are in grooves that run along the main body axis

Where are their specialized tube feet located?

at the anterior end… they form long tentacles

What type of feeders are sea cucumbers?

deposit feeders

how do they gather their food?

tentacles

Sea cucumber respiration

respiration takes place in respiratory tree

… branches from the intestines

how do sea cucumbers “breathe”?

thru their anus by taking water inside their anus to fill the respiratory tree