phylum echinodermata spiny skin. advanced? skeleton is internal test comprised of individuals...
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Phylum EchinodermataPhylum Echinodermata
Advanced? Skeleton is internal test comprised of
individuals plates of porous high-Mg calcite.
Bilaterally symmetrical larvae Adult typically has pentaradial symmetry Water vascular system instead of muscles Highly regenerative – can eviscerate Separate sexes: External fertilization
Light sensitive eyes at the end of each ray – no vision, no brain , no head
Reduced internal organs – no respiratory circulatory, excretory, nervous system
Adults have pentamerous radial symmetry Respiration is by diffusion through skin.
Starfish are scavengers and eat a variety of organisms. They can open a clam
shell a few centimeters wide. Then by inverting its stomach into the shell, the
clam is digested and absorbed.
Missing parts from injury or evisceration are quickly replaced. Any
portion of the central disk will regenerate a new starfish.
Crinoidea Ophiureidea Holothuroidea Asteroidea Echinoidea
Crinoidea ( Feather Stars, Sea lillies)
Upside down brittle star May have a stalk Cirri used like a holdfast Catches food with tube feet Ancient
Ophiurroidea (brittle star)
Arms distinctly set off from central disk Tube feet with no suckers. Moves by
lashing arms Closed ambulacral groove, no gut branches
Holothurudoidea (Sea Cucumber) Soft, cucumber shaped body Suckered tube feet in 5 longitudinal rows Tentacles around mouth (modified tube
feet) Suspension, detritus or deposit feeders
Sea Cucumber Anatomy
Asteroidea (Sea Stars)
Star shaped body Tube feet with suckers Open ambulacral grooves Most have pedicellariae
– Thought to be used in defense
Mostly predators Feed by everting portion of stomach
Sea Star Basic Anatomy
Echinoidea (Urchins and Sand Dollars)
Skeleton = test CaCO3 ossicles are fused
Tube feet with suckers Moveable spines and pedicellariae Feed on algae, encrusting animals Mouth is referred to as Aristotle’s lantern
Exclusively marine: Echinoderms lack osmoregulatory mechanisms that might allow them to live in brackish or fresh water
Urchins may control algae growth on reefs Sea Stars are important inter-tidal predators Make up an estimated 90% of deep sea biomass May regulate growth of sessile organisms