ECHINODERMS

PHYLUM ECHINODERMATA

CHARACTERISTICS

• Radial symmentry
• Several arms (5 or more,mostly grouped 2 left-1 middle-2 right)radiating from a central body.
• Body consist of equal segments,each containing a duplicate of various internal organs.
• no brain nor heart
• with eyespots on each arm
• mouth situated on the underside and anus on the top(except feathers stars,sea cucumber and some urchins).
• contains tube feet with suction pads controlled by water vascular system.
• some are carnivorous while others are detritus foragers 
• reproduction is through release of sperms and egg into the water
• capable of regeneration and fragmentation.

TYPES OF ECHINODERMS

• Class Asteroidea
• Class Ophiurodea
• Class Echinoidea
• Class Holothuroidea
• Class Crinoidea

1.CLASS ASTEROIDEA

• Carnivorous and feed on sponges and mollusks some are specialized feeders.(crown of thorns)
• doesn't have hard mouth parts to help them capture prey



CROWN OF THORNS (ACANTHASTER PLANCI)

Crown of thorns ( Acanthaster planci)
• one of the largest and the most venomous starfish
• size reaches up to 50cm. in diameter
• 10-20 spiny arms with formidable thorn like toxic spines
• feed on coral polyps
• Predators: Triton shell and some puffer fish

2.CLASS OPHIUROIDEA

• close relatives of sea stars
• have five snakelike arms which highly flexible
• no replication on internal organs,just one set in the central disk
• smaller central disk and no anus



SERPENT STARS



• arms  of brittle stars are fragile. (defense mechanism)
• most active and fastest moving echinoderms
• feed on plankton but also on detritus

3.CLASS ECHINOIDEA

Sea Urchins:

• external chitinous skeleton and a centrally located jaw
• some have spherical bulb like cloaca
• movable spines are attached to the body,some are venomous

• locomotion by tube feet but also by movement of the spines on the underside of the body
• generally nocturnal
• most are algal grazers but some feed on the sponges and detritus

4.CLASS HOLOTHUROIDEA

• dont have radial symmetry but are bilateral
• cucumber shaped with elongated muscular,flexible body with mouth at one end anus on the other 
• tentacles present in mouth for food collection 

• feed on rich organic film coating sandy surfaces
• crawl over the bottom and ingest sand
• move by means of tube feet
• releases its digestive tract when threatened (defense  mechanism)

5.CLASS CRINOIDEA

• radial symmetry
• cup-shaped body
• numerous feathery arms project from a central disc
• have 5 up to 200 arms(pinnules)
• nocturnal
• usually cling to sponges

FEATHER STARS

Reporters: 

⚬Ma. Fe Camacho

⚬Merielette Joven

⚬Florencio Angcay