Phylum Echinodermata

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Phylum Characteristics:• Name: (Greek) echinos = spiny; derma =skin• Calcareous endoskeleton in the form of ossicles• Most adults with pentaradial symmetry• Larva with bilateral symmetry• Water-vascular system (including tube feet) for

locomotion, attachment, and/or feeding• Digestive tract• Hemal system (to circulate fluids and possibly

distribute nutrients)• Nervous system (= nerve net, nerve ring, and radial

nerves)

Class Crinoidea• Sea Lilies and feather stars• Most primitive of all living echinoderms• Sea Lilies attach to substrate by a stalk– Unattached end = crown (of 5 branched arms)– Double row of tube feet along each arm– Crown attached to stalk at calyx– Stalk may have cirri (projections)*feather stars lack a stalk and are swim/crawl using

their arms

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http://www.nova.edu/ocean/messing/crinoids/8%20Feeding%20mechanism_files/image004.jpg

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hitecrinoid_forblog.jpgSea Lilies

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http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Ophiuroidea/Feather_Star_large.jpg

Feather Stars

• Suspension/Filter feeding: Tube feet catch prey and cilia in ambulacral groove carry it to mouth

• Lack nerve ring• Can be dioecious or monoecious (male

gametes develop before female gametes)• Fertilization may be external or embryos may

be brooded on arms of adult• Capable of regeneration

Class Asteroidea• Sea Stars (and Sea Daises?)• 5 arms around a central disk, each with an

ambulacral groove and tube feet• Some arms may have photoreceptors/ocelli on

tube feet at tips• Dermal Branchiae (thin folds of body) function

in gas exchange• Some have pedicellariae (pincherlike

structures) which may help clean & protect

• 2 sides: oral/aboral– Aboral side contains

anus and madreporite (connects ring canal to outside -helps to replace water into water-vascular system)

– Oral side has mouth connected to esophagus, stomach (with 2 regions), and short intestine

• Feed on snails, bivalves, crustaceans, polychaetes, corals, detritus, etc.

https://yhsbiology.wikispaces.com/file/view/starfish-1.jpg/33144125/starfish-1.jpg

http://universe-review.ca/I10-82-starfish.jpg

http://www.cals.ncsu.edu/course/zo150/mozley/fall/Asterskin.jpg

http://www.2classnotes.com/images/12/science/Zoology/Aboral_surface_of_star_fish.gif

• Known for regeneration (asexual reproduction)• Most Dioecious (internal difference)– 2 gonads in each arm

• External fertilizationhttp://sharonminsuk.com/LabBio/images/StarfishStagesBig.jpg

http://allencentre.wikispaces.com/file/view/starfish_larva.jpg/31302621/starfish_larva.jpg

http://mrbarlow.files.wordpress.com/2008/03/giant-sea-stars.jpg

http://museumvictoria.com.au/pages/3349/gallery/tinystar.jpg

http://www.tankedup-imaging.com/images/blue_sea_star.jpg

http://photography.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Photography/Images/Content/necklace-sea-star-696678-sw.jpg

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