Phylum Echinodermata Kingdom Animalia

General Characteristics Name means “spiny skin” Exclusively marine Possess a semi-flexible endoskeleton or internal skeleton (made of calcium carbonate and connected by ligaments) Water vascular system and suction-cup-like structures called tube feet most adult forms exhibit pentaradial symmetry (larva show bilateral symmetry) Regeneration – can re-grow some body parts when lost 6. Separate sexes and reproduction mostly sexual but good powers of regeneration by fragmentation.

General Characteristics continued Name means “spiny skin” 7. Developed from deuterostome Coelom forms by out-pocketing of the primitive gut --also called enterocoelomates 9. A complete digestive tract but not a real excretory, circulatory or respiratory system. 10. Segmentation 11. Lack Cephalization

Cephalization Unlike most bilaterian phyla, echinodermata lack any trace of cephalization and any specialized sense organs

Response The nervous system is not highly developed in Echinoderms. A nerve ring surrounds the mouth. Radial nerves connect the nerve ring with the body sections. A variety of scattered sensory cells detect light, gravity, and chemicals released by prey.

SEGMENTATION The ring canal in the center of the starfish has five radial canals that branch off

Respiration & Circulation The water vascular system is responsible for most respiration and circulation. Respiration (in most species) occurs through the thin walls of the tube feet. Few species have small outgrowths called “skin gills”. Nutrients and gases are circulated through the water vascular system.

Excretion Undigested food and digestive wastes (feces) are released through the anus. Cellular wastes are passed through the thin walls of the tube feet and skin gills in the form of ammonia.

Feeding Method varies from species to species Sea urchins use a five-part jaw-like structure to scrape algae from rocks. Sea cucumbers ingest sea floor sediments, digesting out the organic material. (detritus feeders) Sea stars feed on bivalves by pushing their stomachs out of their mouths into the shell of the prey, exuding enzymes, and then digesting the resulting “soup”.

Movement Most move using tube feet (part of the water vascular system) The shape and size of the plates of the endoskeleton help determine the range of mobility. Smaller plates mean increased flexibility and mobility.

General Internal Anatomy

Class Asteroidea: Sea stars Creep along the ocean floor Most are carnivorous, eating bivalves. If a sea star is pulled into pieces, each piece will grow into a new individual as long as it contains a portion of the central disc. Feather Star Basket Star

Class Crinoidea: Sea Lilies They are filter feeders, who have over 50 feathery arms. Sea Lilies are sessile and live on the ocean floor.

Class Holothuroidea: Ex: Sea Cucumber Look like warty moving pickles with a mouth at one end and an anus at the other. Most sea cucumbers are detritus feeders. Some kinds of sea cucumbers use a sticky glue like substance to immobilize their predators.

Class Echinoidea: Ex. disk shaped sand dollars, oval heart urchins, and sound sea urchins. Some are grazers and eat algae, others are detritus feeders Sea urchin’s defense is its long sharp spine. Some even contain small blue poisonous sacs covering the tips of each spine

Classification & Examples: Class Ophiuroidea - Brittle Stars Common on coral reefs Filter feeders and detritovores Hide during the day and feed by night Will shed one or two rays to avoid being eaten totally.

Classification & Examples: Class Holothuroidea Sea Cucumbers Detritus feeders – suck up organic matter and remains of other organisms while crawling along the sea floor Will regurgitate their internal organs in order to avoid predators – then re-grows organs at a later time.