Lecture 13: Echinodermata

Phylum Echinodermata

no brain or head , just oral side & back side

• sea stars, sea urchins, sea cucumbers, sea lilies, brittle stars

defining characteristics of Echinodermata

1. endoskeleton made of calcium carbonate

2. Deuterostomes = first opening in embryo is anus

3. water vascular system : water filled tube system that control movement, breathing & feeding

4. Pedicellaria = tiny pincher like structures on skin that help w/ cleaning & defense

5. Dermal branchiae = tiny skin bump gills that help breathe & rid of waste

6. Pentaradial symmetry = 5 parts but larvae is bilateral

7. lives on ocean floor (benthic)

Subphylum Plematozoa ; Class Crinoidea

sea lilies & feather stars

• attached sessile animals (motile tho)

• epidermis covered in plates

• filter feeders

• DONT have: spines, pedicellariae, & madreporites

what are madreporites for ?

entry valve for the water vascular system in Echinoderms

Subphylum Eleutherozoa & the classes within it:

1. Asteroidea

2. Ophiuroidea

3. Echinoidea

4. Holothuroidea

free living

1. Sea stars

2. Brittle stars

3. Sea urchins

4. Sea cucumbers

Water vascular system labelling

• Madreporite: entrance where water comes in

• Stone canal: carries water from madreporite to ring canal

• Polian Vesicle: story extra water

• Ring canal: circular tube in center of body that distributes water

• Radial canals: tubes that go out from ring canal into each arm

• Lateral canals: one way valves branching off radial canal to tube foot

• Ampulla: a bulb that squeezes water into the tube foot

• Tube foot: used for movement and sticking to surface (suction cups)

what muscles does the ampulla use to squeeza water to the podium (tube foot)?

Circumlongitudinal ampullary muscles (CLD)

Pedicellariae

• removal of debris & unwanted organisms

• protect dermal branchiae

• capture live prey

Ophiuroidea characteristics

• No ambulacral groove

• no pedicellariae

• no dermal branchiae

• arms bend & move for locomotion

Echinoidea characteristics

• Test architecture: 10 rows of plates = 5 zones tube feet + 5 zones of no tube feet

Aristotle’s Lantern

set of 5 sharp teeth in a sea urchin

Holothuroidea

• soft leathery body wall

• small ossicles

• tube feet on ventral side with oral (Trivium)

• less tube feet on dorsal side (Divium)

Holothuroidea respiration

breathe through their anus using respiratory tree

• cloacal muscles contract to open anus

• water enters

• anal sphincter closes and water is forced into tree

• tree contracts and water is pushed out (gas exchange)

where do pearlfish live ?

live in the respiratory tree of sea cucumbers, enter when it inhales, leaves when it exhales.