Seastars, Sandollars, Sea cucumber, Sea urchins Phylum Echinodermata Seastars, Sandollars, Sea cucumber, Sea urchins

A. General Information 1. Includes sea stars, sea urchins, sand dollars and sea cucumbers 2. strictly marine  over 2,000 species 3. Radial symmetry  good advantage

5. Mostly benthic  live on sea floor 4. Echino is Greek for “spiny” and dermata means skin  “spiny skin” 5. Mostly benthic  live on sea floor 6. Complete digestive system  mouth, intestine, and anus 7. Can regenerate lost body parts ***8. Water vascular system  only animal with water vascular system

B. Water Vascular System 1. Used for feeding and locomotion 2. A hydraulic network  uses the power of water to function 3. Found only in echinoderms

4. How it works a. On dorsal side (top) of echinoderm there is a sieve- like plate madreporite - the opening to the water vacular system b. Connected to the madreporite is a short canal stone canal; helps filter-out debris

c. Connected to the stone canal is. a circular canal that runs c. Connected to the stone canal is a circular canal that runs around the central disc  the ring canal d. The ring canal is connected to the radial canals run the length of each arm

e. Located along the radial. canals. are 1000s of “little e. Located along the radial canals are 1000s of “little suction cups” called tube feet  used for locomotion, grasping & feeding f. Tube feet can extend and contract by a balloon-like structure called an ampulla;

Movement of tube feet 11:06 Echinoderms 10

h. Each tube foot has its own ampulla g. ampulla pushes water into tube feet to extend them; “sucks” and hold water to contract them h. Each tube foot has its own ampulla i. The water vascualr system allows the echinoderm to be a persistant predator and have excellent adhesive abilities.

dorsal view 8. arm 7. Anus 5. madreporite 6. Central disk

1. eyespot 3. tubefeet 4. mouth 2. Ambulacral groove Ventral view

19. madreporite 22. Radial canal 20. Stone canal 23. Tubefeet 21. Ring canal

Water-Vascular System of a Sea Star Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Water-Vascular System of a Sea Star Fig. 16.4 16-3

10. ring canal 9. Stone canal 13. radial canal 11. Madreporite 14. Ampulla –not extended 17. ampulla; extended

C. The 5 Classes of Echinodermata 1. Class Asteroidea -Includes the seastars (starfish) -A central disc with five or more arms that radiate in all directions -Mouth on underside (ventral) -Anus on dorsal side (top)

-At end of each arm are eyespots – they’re only light sensitive; -Each underside of arm has ambulacral groove – a deep groove that runs the length of the arm; this is where the tubefeet are housed

Outer skin has projections all over called spines also has gills tiny hairs called cilia tiny pinchers called pedicellariae – main function is to keep the top side of the seastar cleaned so gills do not get clogged

Pedicellaria Spine Pedicellaria Dermal branchia Echinoderms 25

Reproduction in seastars – separate sexes; sperm and eggs are released into water and unite; “baby” seastars start as a bilateral individual then grows into a radial adult

-Sea stars live 3 to 5 yrs. -Sea stars do have great regenerating powers; most have to have a portion of central disc to regrow -Sea stars feed on bivalves (clams, etc…) small crabs, snails & coral

-Sea stars use their 1000’s of tubefeet to eat and to move -Since the tubefeet are part of the “hydraulic” system they have no problem “prying” open bivalves

-The tubefeet wear out the muscle of the bivalve; opens slightly, the seastar inverts its stomach into the bivalve and eats -A sea star can take an hour to a week to feed on one bivalve

2. Class Ophuroidea -Includes brittle stars & basket stars -Have flattened, round central disc -Very delicate, found only in well protected waters or areas -Arms are easily broken off, but have great regenerating powers

-Arms are very slender and flexible -Brittle stars only have 5 arms; basket stars have lots of arms -> looks like a tumbleweed -Arms have sticky secretions to capture prey -Feed on plankton or dead material -Lack an anus, waste exits mouth

-Tube feet have no suction cups, mostly use flexible arms for “swimming” -Feed at night -Arms capture prey and move food to mouth -Separate sexes and outside fertilization

3. Class Echinoidea -Includes sea urchins & sand dollars ****-Lacks arms -Covered with spines -> “Echinos” means hedgehog -have anus, mouth, & large stomach

-Protected by a structure called a. test – “skeletal structure or -Protected by a structure called a test – “skeletal structure or shell” -Mouth consist of five “teeth” that are sharp, teeth from a structure called Aristotle’s Lantern -Very few enemies - spines & teeth, which are not easily digested

-Separate sexes; eggs of sea urchin is high dollar eating -Sand dollars protect themselves by burrowing into sand -Sea urchins attach themselves to rocks, reefs, etc; they have great suction ability

-Both filter in dirt and eat the organic material absorbed by sand or scrape the ground with teeth; some feed on algae -Some sea urchins are poisonous

4. Class Holothuroidea -Includes sea cucumber -Looks like a cucumber -Has no spines, instead has “leathery casing” that can extend or contract, - when contracted, very thick and hard

-Have 5 regions - run from mouth to anus forming a “circular casing” -Have tube feet on 3 regions -Breathe through respiratory tree -When unhappy, sea cucumbers ejects inwards -Can regenerate lost organs

-Feeds by “vacuuming” up. sediments and absorbing -Feeds by “vacuuming” up sediments and absorbing nutrients from the sediments -Releases waste in long “rolled” links -When fully extended it can be up to 6 ft. in length, very soft flexible

-Good eating –> used in soups, jerky, etc… -Found in all oceans even Antarctic -Lives 5-10 yrs.

5. Class Crinoidea -Includes sea lily & feather stars -Oldest living echinoderms & most primitive -Live at depths of 100m or more -Live on a stalk, sea lilies are sessile, so have long stalks; Feather stars are free swimming, and have short stalks

-5 or more arms form a “crown” on end of stalk; arms have more “feathery” attachments (80-200) -Arms wave through the water to capture prey, arms bring food to the mouth which faces ***upwards not downward***

-Feed on plankton, capture with sticky secretions. -Bright colors, neat patterns -Active mostly at night -Arms roll up when resting -Regenerating powers-> several weeks to regrow -Separate sexes->release sperm and egg into water