Animalia-echinodermata

= Echinodermata = Aujan Mehregan

**__Diagnostic Characteristics of Echinoderms__** **Echinoderms,** also known as sea stars, sea urchins, brittle stars, sea cucumbers, and sea lilies are slow-moving animals are coelomates – organisms that have a body cavity. The parts of the animal usually radiate out in the form of five spokes. They have an endoskeleton covered by a thin skin. Most of these animals are prickly due to skeletal protrusions. They have a **water vascular system**, which is a network of hydraulic canals that branch off into extensions, which are utilized in locomotion, feeding, and gas exchange. (AM) **To clarify, they commonly appear with protective spines (or noticeable bumps) that also assist in the respiration process by taking in oxygen. Other facts about echinoderms are that 1) they can only live in salt water, and 2) that there are //thousands// of species! (MB)**

**__Habitats__** Echinoderms are all marine animals. Some attach to rocks, corals, or the sea floor via their **tube feet**, extensions of the main body; others bury themselves under the sand; while still others suspend themselves off rocks. (AM)

Being exclusively marine animals, echinoderms are generally exremely sensitive to changes in marine habitats. They are unable to tolerate changes in the salinity, temperature and light exposure in the water, and move often if an area changes noticeably in such a way. Light is very important, explaining the burying behavior behavior of echinoderms, as they hide during the day and come out at night when the light intensity is lowered. (JP)

The largest habitat of echinoderms is the Great Barrier Reefs. There are more than 800 species of echinoderms there, and many of those species are considered to be rare and not found anywhere else. (MM)

**__Major Types__**


 * 1) //__Asteroidea__ -// This class is better known as sea stars. They have five or more arms that radiate from a central disk, which have tube feet and act like suction cups. The sea star coordinates its tube feet to attach to rocks or to crawl along the floor. Their tube feet are also used to capture food, such as clams. To eat, the sea star turns its stomach inside-out, revealing its mouth. Its digestive system secretes juices to begin digesting the hard shells. Sea stars are capable of regrowing a lost body part, making them able to regenerate. (AM)
 * 2) //__Ophiuroidea__ -// Better known as brittle stars, these animals have a distinct central disk and their arms are long and flexible. Their tube feet don’t have suction cups, and they move by lashing their arms out and pulling themselves in that direction. Some species are suspension feeders; while others are predators or scavengers. (AM)
 * 3) //__Echinoidea__ -//Sea urchins and sand dollars make up this class. They have no arms, but they have five rows of tube feet that slowly move the animal. They have muscles that pivot their spines and aid in moving. They eat mostly seaweeds. Sea urchins have almost a spherical shape, and sand dollars are flattened, disk-shaped animals. (AM) **The Echinoidea whose name means “like a hedge hog” are also covered with spines. Some within this class display radial symmetry while others have seemingly bilateral orientations. (ZJ) **
 * 4) //__Crinoidea__ -//Sea lilies and feather stars use their arms in suspension feeding. They circle the mouth and direct the food upwards toward their mouth. Sea lilies live attached to the substratum by stalks, and feather stars move using their long, flexible arms. (AM) **They are the most ancient and primitive of all the classes of echinoderms although there are 700 or so species that still exist today. (ZJ) **
 * 5) //__Holothuroidea__ -//Sea cucumbers lack spines and they have a thinner endoskeleton. Resembling an actual cucumber, they are elongated echinoderms. Additionally they have five rows of tube feet, which surround the mouth and have developed to aid in feeding. (AM) **Like echinoids the mouth and anus are located at opposite poles on the holothuroid. (ZJ) **



**__Basic Anatomy__** Most echinoderms are prickly due to skeletal bumps. They have a unique water vascular system, which is a network of hydraulic canals that branch off into extensions called tube feet. Echinoderms are bilaterian, and don’t have a true radial anatomy, which means that their mouths and such fall more on one side of the animals instead of being a central attribute. (AM) <span style="color: #337a3a; font-family: Arial,Helvetica,sans-serif;">The central disc of the echinoderm body (like the center of a starfish) is called the pentamorous. Each of the arms branching from the pentamorous has its own set of sense organs, even though the creatures don’t have hearts, eyes, or a brain. Experiments have shown they’re slightly sensitive to light, which is surprising due to their lack of eye. Some Holothuroidea and Echinoidea have been found to have light sensitive organs. (LPE)

<span style="color: #0000ff; font-family: "Comic Sans MS",cursive; font-size: 120%;">The skin of echinoderms usually has warty projections,spines, or both. Echinoderms have radial symmetry, where their body can be divided into five or less similar pieces.Unlike other radially symmetrical animals, they develop from a bilaterally symmetrical larva and retain some level of bilateral symmetry even as adults. There is no head in echinoderms. The surface containing the mouth is called the oral surface, and the opposite side, which usually bears the anus, the aboral surface. (VN)



Echinoderms’ endoskeleton systems are made up interlocking plates and spines, which are made out of limestone, also known as calcium carbonate or CaCO­­3, which is collectively called the stereom. The stereom is porous, as show in the picture below, which helps keep the echinoderms’ skeletons light but relatively durable. (MR; Sources 20 and 21)

<span style="color: #367c37; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**__Transport of Materials__** <span style="color: #367c37; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Echinoderms, just like most other animals transport most of their oxygen via special proteins called **respiratory pigments**. The proteins circulate with the blood. They use these proteins to ensure enough oxygen is being circulated during metabolism. Echinoderms also have digestive glands and aid in the absorption and storage of nutrients. Each tube foot has a suckered podium, which expands and extends the substratum when water enters. The podium shortens and forces water back into the ampulla. This ensures adequate oxygen and carbon dioxide exchange. (AM) Water vascular system - consists of the madreporite, the stone canal, the ring canal, radial canals, ampullae and tube feet. Transport system - body fluids circulate throughout the tissues Haemal system - doesn't do much in most echinoderms except sea cucumbers. Its main function is to act as a "blood system"(MP). (continuation of water vascular system) This is a hydraulically controlled system consisting of a **circumoral ring** around the esophogus with connecting radial canals each leading to an ambulacrum. The radial canals in crinoids run along each arm into a groove and tube feet. The groove with its many cilia and hydraulically driven tube feet manipulate captured food down the grooves along the arms down to the mouth. Echinoderm water vascular systems are either open or closed.If the radial canals run down the grooves and are not covered by plates then the system is considered "open", if the radial canals are primarily internal and externalized through pores, the system is "closed". (RW)

Echinoderms have fairly large stomach areas. One interesting fact about the echinoderm starfish is that they are able to flip their stomachs to the outside of their body in order to get food from animals such as clams by inserting their stomach into their prey. Echinoderms digestive track mainly consist of their mouth where food enters which is sometimes on the bottom while the anus can sometimes be on the top in addition to their stomach area. (CP source 15)

Echinoderms’ water vascular system happens to be particularly unique; this is because their circulatory system uses seawater and not blood as the circulatory fluid. (MR; Source 19)

<span style="color: #337a3a; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**__Reproduction__** <span style="color: #337a3a; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Sexual reproduction in echinoderms occurs when each, male and female echinoderm, individual releases its gametes (sperm and eggs) into the water. The larvae have bilateral symmetry, and the radial anatomy of adult echinoderms is a secondary adaptation to a slow-moving lifestyle. (AM)

<span style="color: #337a3a; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">At around 3 minutes into this video, you can watch a female crown-of-thorns starfish spawn and release nearly 30 million eggs into the water! (IL) media type="youtube" key="wS15dEQXBTM" height="315" width="420"

<span style="color: #337a3a; font-family: Arial,Helvetica,sans-serif;">When starfishes are about to reproduce, they gather in groups when ready to create gametes. Some female starfishes may have eggs held by the females on their pyloric stomach. The starfish and other Echinoderms use environmental timings to coordinate the time, and chemical signals to convey sexual readiness to the population. After fertilization occurs, the egg grows using yolk or by consuming nearby plankton. The larvae has a similar lifestyle to a plankton, living in the water and beating cilia to move. Some larvae stay attached to the female, and sometimes might even be attached to the ground by the mother. This depends on the nearby environment. Polar, deep-sea and other unfavorable environments tend to have species that care more for their young. The larvae has bilateral symmetry, contrary to to adult echinoderms. After time has passed, the larvae will go through metamorphosis to settle at the bottom, and grow into adults. (AR)

<span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 14px; text-decoration: none; vertical-align: baseline;">Asexual reproduction involves the regrowth of missing body parts by dividing a specific body part into 2 pieces. This process is know as fission but is only possible if the creature can regenerate its body wall by sealing the wounds off. An example is a sea star successfully regrowing one of its arms by deliberately breaking an arm off its central disk and dividing it into 2 pieces. (AP)

Not only can echinoderms regenerate individual body parts, but they can also create new organisms. If a part of an echinoderms core is broke off, it will develop into a complete animal. (MR; Source 19)

<span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 14px; text-decoration: none; vertical-align: baseline;">media type="youtube" key="f7cXeWxxfD4" height="315" width="560"RJ **__Environmental Adaptations__**

Echinoderms adapt to their environment by using small protrusions on their skin for gas exchange. The outfoldings of the body surface, **gills**, are found all over the body (Figure a). The surface area of the gills is much greater than that of the rest of it body. Since echinoderms live in a salty, aqueous environment where oxygen is not very abundant, **ventilation** helps them by increasing the flow of the gases in the medium over the gills. (AM)

Despite lack of complex sense organs, the nervous systems on each arm can process light, water, position, and temperature. Tube feet and skin respond to touch. (LPE) Fossil Record Fossil record for echinoderms started around the early Cambrian period. Starfish started appearing in the Ordovician period. (CM)



= Acquiring and Digesting Food = Echinoderms have many different methods of feeding. These methods include predation, parasitism, filter feeding, and deposit feeding. In some species, a modified arm is used as a filter in the water to capture prey and nutrients. Some examples of different methods of feeding are found in the three most dominate echinoderms, starfish, sea urchins, sea sponges. Starfish invert their stomach over their prey, allowing their food to be digested externally. The sea urchin uses a tooth baring jaw structure known as Aristotle's Lantern to scrape algae off of rocks to be consumed. Finally, the sea sponge vacuums up sand and filters any organism in the sand, expelling clean sand through the anus. (MS 18)

//<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">he diagnostic characteristics that define the group // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Acquiring and digesting food // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Sensing the environment // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Locomotion // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Respiration // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Metabolic waste removal // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Circulation // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Self protection // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Osmotic balance // //<span style="background-color: #ffffff; font-family: Calibri,sans-serif;">Temperature balance //

Review Questions: 1. What are some defining physical characteristics of echinoderms one could observe and what are the evolutionary explanations for these characteristics? (BT) 2. How do echinoderms display radial symmetry in some ways, and bilateral symmetry in others? (Matt B) 3. Describe the advantages to being a ceolomate. (RK) 2. How have echinoderms adapted to the salty, oxygen-poor environment they live in in terms of respiration? (PS) 5. Why do echinoderms' appearances and structures vary so greatly? Why are they grouped together taxonomically if they have such apparent differences? (JS)

**__Citations__**

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**-** Campbell, Neil A., and Jane B. Reece. "Chapter 33: Invertebrates." //Biology//. 6th ed. San Francisco: Pearson Education, Inc., 2002. Print. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**-** Campbell, Neil A., and Jane B. Reece. "Chapter 42: Circulation and Gas Exchange." //Biology//. 6th ed. San Francisco: Pearson Education, Inc., 2002. Print. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**-** Zubi, T. (2011, April 22). Starfish. Retrieved from http://www.starfish.ch/c-invertebrates/seesterne.html <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**-** Koksheng. (2009, May 25). Echinoderm Hangout at Changi. Retrieved from http://wondercreation.blogspot.com/2009/05/echinoderm-hangout-at-changi.html <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**-** Watanabe, J. (2011 February 12). Phylum Echinodermata: Subtidal Sea Urchins, Sea Cucumbers, and Brittle Stars. Retrieved from http://seanet.stanford.edu/EchinoHoloOphio/index.html <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**-** Tan, R. (2008). Red Feather Stars. Retrieved from http://www.wildsingapore.com/wildfacts/echinodermata/crinoidea/red.htm <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**-** Buescher, C. (2011 May 22). Class Holothuroidea, the Sea Cucumbers. Retrieved from [] <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">- "Starfish Reproduction." //Madreporite Nexus//. Web. 29 Oct. 2011. <http://www.madreporite.com/science/reproduction.htm>. (AR)

Zubi, Teresa. "Echinoderms (starfish, Brittle Star, Sea Urchin, Feather Star, Sea Cucumber)." //Starfish: Photos of Fishes, Invertebrates (molluscs, Crustaceans, Echinoderms, Worms, Corals, Sponges, Jellyfish and More), Reptiles, Rays and Sharks. Start Your Dive into the Coral Reef!// 13 Mar. 2010. Web. 25 Oct. 2011. []. (LPE) "echinoderm." //Encyclopædia Britannica. Encyclopædia Britannica Online//. Encyclopædia Britannica Inc., 2011. Web. 25 Oct. 2011. (LPE)

http://www.mcwdn.org/Animals/Starfish.html (MB)

<span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 14px; text-decoration: none; vertical-align: baseline;">"Echinoderms (starfish, Brittle Star, Sea Urchin, Feather Star, Sea Cucumber)." Starfish: Photos of Fishes, Invertebrates (molluscs, Crustaceans, Echinoderms, Worms, Corals, Sponges, Jellyfish and More), Reptiles, Rays and Sharks. Start Your Dive into the Coral Reef! Web. 30 Oct. 2011. []. (AP)

[] (JP) [](MP) "Echinoderms" 30. Oct 2011 [] (MM)

http://youtu.be/f7cXeWxxfD4 (rj)

"Echinodermata."The Columbia Encyclopedia, Sixth Edition. 2008. Retrieved November 06, 2011 from Encyclopedia.com: []

(VN)

<span style="background-color: #ffffff; color: #336699; display: block; font-family: "times new roman"; text-align: left;">15. <span style="background-color: #ffffff; color: #336699; display: block; font-family: "times new roman"; text-align: left;">"Echinoderms." //<span style="background-color: #ffffff; font-family: "Times New Roman",Times,serif; font-size: 16px;">VirtEd //. Web. 06 Nov. 2011. <http://www.virted.org/Animals/Starfish.html>. (CP)

<span style="background-color: #ffffff; color: #336699; display: block; font-family: "times new roman"; text-align: left;">16. <span style="background-color: #ffffff; color: #336699; display: block; font-family: "times new roman"; text-align: left;">[] (RW) <span style="background-color: #ffffff; color: #336699; display: block; font-family: "times new roman"; text-align: left;">17. <span style="background-color: #ffffff; color: #336699; display: block; font-family: "times new roman"; text-align: left;"><span style="color: #333333; font-family: Arial,sans-serif; font-size: 9pt;">Barnes, Robert. //<span style="color: #333333; font-family: Arial,sans-serif; font-size: 9pt;">Invertebrate Zoology //<span style="color: #333333; font-family: Arial,sans-serif; font-size: 9pt;">. 2nd. Philadelphia, PA: W.B. Saunders Company, 1969. Print. (ZJ)

18. "Echinoderms." //Http://www.reefed.edu.au//. Web. 11 Nov. 2011. <http://www.reefed.edu.au/home/explorer/animals/marine_invertebrates/echinoderms>. (MS) 19. "Echinoderm." UXL Complete Life Science Resource. Ed. Julie Carnagie and Leonard C. Bruno. Detroit: UXL, 2009. Gale Science In Context. Web. 28 Nov. 2011. 20. "Echinoderm." Biology. Ed. Richard Robinson. New York: Macmillan Reference USA, 2009. Gale Science In Context. Web. 28 Nov. 2011. 21. Hyman, L. H. 1955. The Invertebrates. Volume IV: Echinodermata. McGraw-Hill, New York.