phylum echinodermata the spiny skin animals examples: sea stars brittle stars sea urchins sea...
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Phylum EchinodermataThe Spiny Skin AnimalsExamples: Sea StarsBrittle StarsSea UrchinsSea CucumbersSea Lilies Feather Stars
Pentamerous radial symmetryBody is arranged around a central axis in 5 parts
Water Vascular SystemUnique organ system that water-filled tube and water pressure for both locomotion and feeding.System of tubes end in tube feet.
Internal SkeletonConsists of plates calcium carbonate (CaCO3).Plates are often studded with spine, hence their name.Typically divisible in 5 parts
Bottom DwellersBenthicMost abundant on rocky shoresCan be found in every ocean, at all depths
Class Asteroidea: Sea StarsFound from subtidal to deepest part of oceanFive appendages (arms) radiating from a central axisEat mussels and are considered pests by seafood industryExamples:Bat Star (Pateria)- W. Coast, Kelp bedsSun star (Solaster)- 10 15 arms, eat other sea stars
RespirationSkin Gills- ciliated finger-like projections on the dorsal surface of the skinBreathe through their skin and tube feetCoelom- fluid filled sac lined with cilia that beat and circulate water. Diffuse O2, CO2, and wastes
Feeding and LocomotionArms are used for locomotion and getting food.Carried out by the Water Vascular SystemWater enters the madreporite (sieve plate) stone canal Ring Canal Radial Canal Tube feet
Tube feet are delicate projections attached along the side of the radial canal in a groove
Feeding and LocomotionAmpulla- top of the tube foot, resembles a medicine dropper.Feet suction to surfaces. Allows sea stars to attach to bivalves and pull open shells by tugging for hours therefore weakening the adductor muscles.Sea star pushes its stomach out through the mouth and digests the food externally.
Figure 2823The Anatomy of a Sea Star
ResponseEyespots- tiny light receptors located at the end of each arm (orange in the picture). Light is converted into electrical impulses that are carried to central nerve ring around the mouth which then directs the arms.
ReproductionSexuallyGonads are located inside each arm near the central disk. Fertilization and development occur externally In the picture are different phases of new organisms from single-celled organisms to larva.
RegenerationSea stars can regenerate new arms if cut offA new Sea Star can grow from an arm as long as part of the central disk is present. In the photo a Northern Sea Star is regenerating two arms. It will take over a year!
Class EchinoideaSea Urchins and Sand DollarsOval or round bodies; lack arms; use spines and tube feet to move; eat algae off rocks using Aristotles Lantern (5-toothed mouth structure)
Protection and PredationUse spines to wedge themselves into spaces between rocks; protects from wave action and predators (except California Sea Otter!)
ReproductionSimilar to sea starUsed for embryological studies because of blastula phase of urchin.
Sand Dollars and Sea BiscuitsSand Dollar: short spines cover its skin; burrow in sand and feed on plankton.Sea Biscuits: more rounded body; longer spines; lives around coral reefs.
Class OphiuroideaBrittle StarsSolitary, nocturnal creatures that hide under rocks during the day.Found in intertidal zone to the deep; from tropics to ArcticUse long muscles in long, skinny arms in order to scurry rapidly about on the sea floor.Can detach appendages when attacked.Brittle stars on a sea cucumber.
Class CrinoideaSea lilies and Sea FeathersMost ancient of echinodermsHave feathery appendages to catch food (plankton)Limited movement. Sea lilies are sessile; Sea feathers slowly crawl on coral reefs.
Class HolothuroideaSea CucumbersSoft, oblong body w/no arms; tube feet arranged in five rows; no endoskeleton or spines; only have small bony pieces in the skinUse sticky branching tentacles (enlarged tube feet) to trap microscopic organisms. Extend around mouth during feeding and retracted when disturbed.No skin gills- take in and release water thru anus and gas exchange occurs in the coelom across membranes call the respiratory treeIf attacked, SC will release its digestive organs to leave a meal for the predator and escape.
Sea Star Pre-labLabel the starfish in your notes.Color the digestive organs red.Color the water vascular system light blue.Color the reproductive glands purple.Color the skin orange.Color the madreporite dark blue.