Phylum Echinodermata There are more than 5000 species of Echinoderms. Echinoderms have spiny skins.

Defining Characteristics A complex series of fluid filled canals with numerous flexible feeding and locomotory appendages 5 pointed radial symmetry in adult Exclusively Marine Body unsegmented Larvae bilaterally symmetrical With unique water vascular system Digestive system complete Respiration by dermal branchae, tube feet, or respiratory tree No kidneys Dioecious Locomotion by tube feet, and/or arms

External Anatomy

Larval Echinoderms showing bilateral symmetry

Echinoderms Skeleton Have an internal skeleton of calcium carbonate Ossicles vary in size and structure and are manufactured by specialized cells

Water vascular system A separate coelom is used with interconnecting fluid filled tubes and canals A ring canal circles the mouth and gives off 5 radial canals The radial canal is exposed and runs along the ambulacral groove

Water Vascular System

Water Vascular System

Tube Feet The ampullae is a small ball that sits above the tube foot Contraction and expansion of the ampulla accomplishes movement They also have a water vascular system that enables them to store water in their tube feet so they can survive while the tide is out.

Mutable Connective Tissue Another unique Echinodermata characteristic is the presence of mutable connective tissue

Higher Classification Echinodermata Class Asteroidea – sea stars Class Ophiuroidea – brittle stars Class Echinoidea – sea urchins Class Holothuroidea – sea cucumbers Class Crinoidea – sea feathers

Class Asteroidea

Sea Stars The oral surface of each arm has a single ambulacral groove Have a large coelom where all the main organs occur

Sea Star Feeding Feed mainly on slow moving, sedentary, or sessile invertebrates Some species evert the stomach onto prey and digest externally, others swallow whole

Pedicellariae Specialized pinchers found on the aboral surface.

Reproduction Sexual Reproduction Can reproduce asexually by disk division Sexual Reproduction Dioecious with sperm or eggs produced in 2 or more gonads in each arm Larval stage = bipinnaria

Regeneration Many species autotomize, leaving predators with a nutritious souvenir while they escape Most spp. can regenerate from fragments that include the disk

Class Echinoidea Ossicles are joined to form a rigid test Defining characteristics Ossicles are joined to form a rigid test Adults possess a feeding structure called Aristotle’s lantern Two attributes: mobile spines, and hollow skeleton or test

Aristotle’s Lantern

They use these spines for protection against predators. The spines also act like stilts to keep their bodies up off the ground so the tube feet can pull them around! They eat mostly algae. They live mostly attached to rocky crevices, which protect them from waves and tide surges. They have become a popular item to eat and are being harvested in alarming numbers.

Sea Urchin Structure

Anatomy of a Sea Urchin

Pedicellariae Pedicellariae prevent fouling of test and are used in defense More complex than sea stars and are located on tall moveable stalks

Ingestion and Digestion Feed on alga material, encrusting bryozoans or scavenge Food is chopped by 5 sharp pointed teeth The digestive system is long to deal with vegetable manner The anus is located aborally

Sand Dollars Irregular: non-spherical variously depressed Anus is shifted to the oral surface posterior to the mouth creating bilateral symmetry The star pattern seen on top of the sand dollars is actually caused by special breathing tube feet! The mouth is found on the under side of the animal.