By: Laura Hein, Jaeyoung Kim Period 3 Rall ECHINODERMATA By: Laura Hein, Jaeyoung Kim Period 3 Rall http://www.palaeos.org/images/thumb/5/5a/Acanthaster_planci.jpg/340px-Acanthaster_planci.jpg

Phylum: Echinodermata Classes: Ophiuroidea: brittle stars Asteroidea: Sea stars Echinoidea: sea urchins sand dollars http://people.hws.edu/mitchell/cards01/LEI2.html

Classes: cont. Crinoidea: sea lillies Holothuroidea: sea cucumbers http://people.hws.edu/mitchell/cards01/LEI2.html

Laura Hein Body cavity (coelom)   -Echinoderms form their coeloms as outpocketings from the archenteron (embryonic gut), -process=enterocoely. -In most species, the coeloms are trimerous, and initially bilaterally symmetrical. -some coelom departments are similar and may reflect a common evolutionary ancestor within the phylum: - left mesocoel gives rise to most or all of the water vascular system, and one or both somatocoels form the lining of the body cavity. Laura Hein

Body Symmetry Radial (pentameral) Jaeyoung Kim http://webs.lander.edu/rsfox/rsfoximages3/lab1_x550_x_595x.gif Jaeyoung Kim

Nervous System Decentralized nervous system Radial nerves run under the ambulacra (legs) Central nerve ring surrounds the gut Eyespots that can detect light No specialized sensory organs and no definitive brain The arrangement of the central nervous system of echinoderms is quite different from that in other deuterostomes. Radial nerves run under each of the ambulacra, and contain the cell bodies of almost all motor neurons and interneurons. A central nerve ring surrounds the gut, and is composed primarily of fiber tracks connecting the radial nerves. No known echinoderm contains anything that could be called a brain, although ganglia are present along the radial nerves in some echinoderms. Unlike most bilaterian phyla, echinoderms lack any trace of cephalization, and have no specialized sense organs. Sensory neurons are located primarily within the ectoderm of podia, and send axons to the radial nerves. Jaeyoung Kim http://www.brocku.ca/MeadProject/Angell/Angell_1906/images/ang01_06.gif

Circulatory Structures -A Echinoderm has water pumped through its body as part of its very simple circulation system -no specific structures for the circulatory system Hemal system of water pumps through the coelom. http://tolweb.org/Echinodermata Laura Hein

Digestive/Excretory System Tubes grab onto food -> invert their stomach -> secrete/squirt juices (enzymes) that digest -> reabsorb digested food through mouth under the center -> wastes out the aboral anus http://image.tutorvista.com/content/animal-kingdom/starfish-anatomy.jpeg Jaeyoung Kim

Locomotion Vascular system consist of a network of hydraulic canals branching into extensions called papullae (tube feet), which provides: slow movement feeding and gas exchange Tube feet uses hydraulics to create negative pressure which acts as a suction force. Jaeyoung Kim

Laura Hein Skeletal type -Biomineral matrix composed of calcium carbonate and several proteins -calcite is composed of numerous tiny crystals lie on same crystal axis within an ossicle -because of this, ossicles are sponge-like microstructures called stereom that is unique to that phylum -Embryologically, echinoderm ossicles are a true endoskeleton, since they are produced by mesenchymal cells and are usually covered by epidermis -However, they act more like an exoskeleton, lying just under the epidermis and enclosing most other tissues in a flexible but tough covering. http://www.esu.edu/~milewski/intro_biol_two/lab__13_echinoderm/images/aster_ossicle_diagr.jpg Laura Hein

Sensory Structures/Features -rudimentary senses including: -light sensitive eyespots sensory tentacles (modified tube feet) at the tips of the arms small patches of cells sensitive to chemicals or touch. http://www.sfdj.com/learn/13.jpg Starfish Tube Feet Laura Hein

Reproductive System Most are dioecious, with separate male and female individuals, but some are hermaphrodites. Each arm contains two gonads, which release gametes through openings called gonoducts, located on the central body between the arms. dioecious Jaeyoung Kim http://egate.mcgehee.k12.la.us/faculty/jenniferz/biology/starfish%20B/STARFISH%20project/rep.%20diagram%20pic.gif

Unique Features Can regenerate lost limbs Jaeyoung Kim http://www.esu.edu/~milewski/intro_biol_two/lab__13_echinoderm/images/aster_diagr_water_vasc.jpg Jaeyoung Kim

Quiz 1.Which of the following is not a sensory structure of the echinodermata A) Light sensitive eyespots b) Sensory tentacles (modified tube feet) at the tips of the arms c) Small patches of cells sensitive to chemicals or touch. d) Taste Buds 2. Which of these do not belong to the echinodermata phyla? a) Starfish b) Brittle Stars c) Jelly Fish d) Sea Cucumbers 3. What kind of circulatory system does the echinodermata possess? a) No specific structures for the circulatory system b) A system of capillaries running throughout the body c) A heart with arteries, blood vessels, veins, and capillaries d) A simple heart-like organ with no separate ventricles 4. Free Response: What are the steps to the digestive/excretory system of an echinodermata?

Answers 1. A 2. C 3. A 4. See slide 8.