Phylum Echinodermata

The Basics Symmetry ▫ All echinoderms have pentaradial symmetry ▫ BUT… they develop from bilateral larvae  Body Openings ▫ Two, mouth & anus

Classifying Characteristics All echinoderms share several characteristics: Endoskeleton made of plates called ossicles. ▫ Ossicles attached to spines or spicules protruding through the skin. ▫ Enchinoderm = “spiny skin” Water Vascular System ▫ Network of water-filled canals inside body Tube Feet ▫ Small extensions of the water vascular system Aid in – feeding, movement, respiration, excretion More closely related to Chordates than other Invertebrates ▫ Develop as deuterostomes rather than protostomes ▫ Larva develop with bilateral symmetry

Reproduction & Feeding: Echinoderms reproduce sexually, with both external fertilization & development. Echinoderms feed in many different ways: ▫ Carnivores, Filter Feeders, Scavengers, etc.

Classification 7,000 Species, 6 Classes

Class Asteroidia Name Means “starlike”: sea stars Tube Feet are used in: Tube Feet ▫ Movement Movement ▫ Capturing Prey Capturing Prey ▫ Gas Exchange Have TWO stomachs – Cardiac and Pyloric ▫ Digestion occurs in this order: Digestion occurs in this order:  Cardiac Stomach – Pyloric Stomach – Digestive Glands Remarkable Regeneration

Class Crinoidea Examples = crinoids ▫ Sea lilies, and feather stars Minimal movement ▫ Sea lillies are sessile as adults Sea Lily Feather Star Click Picture to See Video

Class Ophiuroidea Name means “snake like”snake like Examples = basket stars & brittle stars Characterized by long narrow arms which allow quick movement. They will often break these arms off in order to escape a predator. Basket Star Brittle Star

Class Echinoidea Name means “spine-like” Example = Sea Urchins and Sand Dollars Click on the picture to view Sand Dollar Movement

Class Holothuroidia Name Means “water polyp” ▫ When their tentacles are extended they resemble the polyp form of some cnidarians Examples = Sea Cucumbers Live on the sea bottom ▫ Crawl and burrow into soft sediment Hairy Sea Cucumber Clip

Interesting Extras… After watching ALL of the video clips, what did you find interesting? Watch this last Planet Earth Clip. What else can you add to the list?Planet Earth Clip

Importance: Major part of food webs Very sensitive to environmental changes, used to monitor changes. Food Sources: people consider urchins and cucumbers delacacies Medicine: Sea cucumbers are often used as a healing agent. Sea urchins release so many eggs, in fact, that they are often used to study chordate development.

HW Questions: 1.Explain two reasons why echinoderms, in spite of their radial symmetry and simple bodies, are more closely related to chordates than to the rest of the invertebrates. 2.Starfish are known for their incredible ability to regenerate. Provide a logical explanation for why doctors are studying these abilities so closely.