EchinodermsThu Truong

Phylum: Echinodermata

"echino" - sea urchin, "spiny""derm" - skin

Example animals:StarfishBrittle StarSea UrchinSand dollar

General Characteristics

• Larvae - Bilateral Symmetry, cilliated, free-swimming• Adults - Pentaradial Symmetry• Endoskeleton - consists of calcium carbonate plates and spines,

w/ thin cilliated epidermis• Pedicellariae - modified spines, pincer-like, keeps surface clean• Water Vascular System - network of fluid-filled canals that

function in locomotion, feeding, and gas exchange.• Branches of the  WVS become extended when filled with fluid

(tube feet)• Ampulla - round muscular sac at the base of the foot,

stores fluid and operates tube foot• Well developed coelom, but no excretory organs.• Digestive system most prominent, simple nervous system• Sexes are separate, both eggs and sperm are released into water

Class: Crinoidea

• Anatomyo Stalk - makes them sessileo "arms" resemble feather structure

• Feeding/Behaviorso Remove suspended food from watero Oral surface is on upper side of disko Tentacles coated with mucus to capture organisms

Class: Asteroidea

• Anatomyo  Central disk, has 5 to more than 20 arms - tube feet underneatho Mouth lies on underside of the disco Endoskeleton - series of calcareous plates, enables limted

movement, moves slowly• Feeding/Behaviors

o Carnivorous, eats by attaching itself to prey and secretes digestive enzymes

• Gas Exchange/Secretiono Poorly developed circulatory system, rely mainly on coelom

and coelomic fluido Wastes are diffused outside through the tube feet and dermal

gills• Reproduction

o Sexual or Asexual

Class: Ophiuroidea

• Anatomyo Bodies similar to asteroidea, but the arms are more slender,

enables it to move quickero Tube feet not used in locomotion 

• Feeding/Behaviorso Tube feet used to collect and handle food

Class: Echinoidea

• Anatomyo  Have NO arms, skeletal plates are flattened into a solid shell

called a testo Sand dollars have flat bodies adapted for burrowingo Sea urchins have bodies covered with spines, move by tube feet

• Feeding/Behaviorso Sand dollars feed on tiny organic particles in sando Sea urchins feed on algae on the ocean floor with

calcareous teeth

Class: Holothuroidea

• Anatomyo Elongated flexible body (muscular sac), mouth surrounded by

circle of tentacles (modified tube feet)o Reduction of endoskeleton to microscopic plateso Highly developed Circulatory system, transports oxygen +

nutrients• Feeding/Behaviors

o Slow, live on bottom flooro Eviscration - digestive tract, respiratory structures, and gonads

ejected from body (unfavorable conditions)• Response to Stimuli

o if irritated will attack (shoots red tubules)