Echinodermata

What is Patrick?

• Patrick is a starfish, an echinoderm.

Anatomy

Symmetry

• Evolved from organisms with bilateral symmetry
• Larvae have bilateral symmetry
• Adults have pentaradial symmetry

Skeleton

• Made up of ossicles
• Ossicles = small elements that are embedded in the dermis
• Ossicles provide rigidity and protection (made of calcite crystals)
• May have spines, granules, or warts sticking out of them
• Eg: Shell of Sea Urchins is covered with ossicles in order for protection

Epidermis (skin)

• Includes pigment and mechanoreceptor cells sensitive to environment
• Contain pigments such as carotin, melanin, and carotinoids
• Pigment colors can change depending on prescence of light

Water Vascular System

• Allows echinoderms to move, breathe, and transport waste
• Radial canals are connected to thousands of tube feet
• To move, muscles push water into tube feet

Untitled Slide

Water Vascular System in Sea Stars

• Enters sea star through madreporite (tiny opening on top)
• Flows to a circular ring canal in middle of echinoderm
• Circular ring branches into many different canals (one for each foot)
• Ampullae are balloon like structures; tails are connected to suckers 
• When muscles flex, ampullae swell and contract, causing a push

Nervous system

• Radial nervous sytem
• Net of neurons at center of echinoderm, which forms a ganglia
• Ganglia is a junction of neurons
• Sea urchins have statocysts, which track balance of echinoderms 
• Statocysts contain statoliths moving in a sac

Regeneration

Regeneration in Echinodermata

• Sea urchins can regenerate spines if they have lost some of them
• Sea starts regenerate arms; seperated arms can form new organisms

Stem cells

• Epimorphosis is when mature cells revert back to stem cell status
• Differentiated and designated to different job

ECOLOGY

Food chain

• Predators of sand dollars include a variety of species
• Include sea otters, sharks, gulls, crabs, mollusks, and Arctic foxes 
• Echinodermata controls seaweed population by consumption
• Graze ocean floor
• Control spread of algae

Consumption of Echinodermata

• 50,000 tons of sea urchins are eaten each year
• Echinoderms are consumed in Japan, France, China, and Peru

Medicinal Applications

• Sea cucumber toxins found to kill some types of cancer cells
• Sea urchin genes are related to diabetes, cancer, and Parkinson's
• Studied in developmental biology (study of development of organs)

Taxonomy

Taxonomy of echinodermata

• Comes from kingdom animalia

Main Classes of eleutherozoa

• Edrioasteroidea
• Holothuroidea
• Concentricycloidea
• Asterozoa
• Echinozoa

Edrioasteroidea

• Extinct class of echinodermata
• Pentaradial symmetry
• Sessile organisms
• Consists of ambulacra - feeding groves in upper part

Holothuroidea (sea cucumbers)

• Mouth and anus at seperate ends
• Ossicles imbedded within leathery skin
• In mouth is a perioral ring (series of plates)

Concentricycloidea

• Discovered pretty recently in 1986
• Flat bodies that are very thin (1 cm) 
• Species were located on wood in deep waters
• Water-vascular system
• no arms or mouth (absorb through body wall) 

Asterozoa

• Echinoderms with star-shaped body 
• Central disc which bears mouth on the underside
• Tube feet on lower part of body
• Symmetrical arms
• Include Asteroidea, Somasteroidea, and Ophiuroidea

Echinozoa

• Typically has spines
• 2 main groups: Echinoidea (sea urchins and sand dollars)
• Cyclocystoidea
• Lack of arms and extensions

Classification

Regularia
And
Irregularia

Regularia

• Strict pentamere symmetry
• Long spines 
• Grazes on top of sea floor
• Seperates into different groups 

Irregularia

• Pentamere symmetry and still has bilateral symmetry 
• Mouth is nearer to the front
• Anus is posterior
• Depost feeders (feeds on specks of organic matter)
• Does not seperate into different groups

Evolution

Evolution

• Stem-group echinodermata (Lower Cambrian)
• Homalozoa (Middle Cambrian - Middle Devonian)
• Pelmatozoa (Middle Cambrian -> Now)
• Eleutherozoa(Early Cambrian -> Now)

Stem-Group Echinodermata

• Spirals of overlapping ossicles
• Mouth has "groove"
• Lived in burrows
• Extended bodies outward to feed

Homalozoa

• Some were bilateral
• Two types of ossicles: marginalia and centralia
• appendage (use unknown)

Pelmatozoa

• Sessile
• Cup-shaped head (calyx)
• From calyx are arms (brachia)
• Connected via a stem
• Include Cystoidea, Blastoidea, and Crinoidea (sea lilies)

What has evolution done?

• Evolution has caused the echinodermata to become more efficient
• More flexible while still keeping its strength in its shell
• "Cleaners" of the sea

Thanks for listening!