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The Fascinating World of Asteroidea

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The Fascinating World of Asteroidea - Page Text Content

S: The Fascinating World of Asteroidea

BC: This book explores the fascinating world on Class Asteroidea, the Sea Stars. You will discover some of the amazing abilities that have allowed sea stars to survive in every corner and depth of our oceans for millions of years!

FC: The Fascinating World of Asteroidea | By Ryan Howe

1: The Fascinating World of Asteroidea | By Ryan Howe | - As he got closer he called out, "Good morning! What are you doing?" The young man paused, looked up and replied, "Throwing starfish in the ocean." "I guess I should have asked, why are you throwing starfish in the ocean?" "The sun is up, and the tide is going out, and if I don't throw them in they'll die." "But, young man, don't you realize that there are miles and miles of beach, and starfish all along it. You can't possibly make a difference!" The young man listened politely. Then bent down, picked up another starfish and threw it into the sea, past the breaking waves and said, "It made a difference for that one." - -The Starfish

2: Table of Contents | 4-5.......................Echinoderms 6-7.......Asteroidea (The Sea Stars) 8-9..........................Physiology 10-11.......Geographic Distribution 12-13...........................Feeding 14-15....................Reproduction 16-17................Crown of Thorns 18-19..............Impact of Humans

4: Echinoderms | A brittle star, member of the class Ophiroidea, meaning "snake like". | This is a perfect example of traditional crinoids, feather stars. Although at first they may look like a sessile seaweed or a marine fern, they are actually quite motile, but prefer to sit in a good spot and use their "feathery" arms to catch planktonic particles. | Phylum Echinodermata, the echinoderms, is one of the most diverse phyla of invertebrates to inhabit our oceans. There are several classes within phylum Echinodermata, Cridoidea (the feather stars), Ophiroidea (the brittle stars), Echinoidea (the sea urchins), Holothuroidea (sea cucumbers), and the most well known class: Asteroidea (the sea stars).

5: Unlike most echinoderms, sea urchins lack long pairs of arms and instead, have opted for security over speed. They live safely within their hard test, which is covered in sometimes hundreds of opposable spines that are often poisonous. But being long and sharp is usually enough deterrence for a hungry fish. | FUN FACT: the name echinodermata is based off of the root word "echino", which is Latin for "spiny", similar to an Echidna. | Members of the class Holothuroidea really do resemble their namesake, but some like the Sea Pig on the right have developed special appendages for speedy movement and keen perception in the dark depths of the ocean.

6: The Sea Stars | Class Asteroidea is the most recognizable of the echinoderms. They are everywhere in our lives. They appear as cartoon characters, delicate decorations, and as food for some people. But it is not surprising how big a part sea stars are in our lives, when they play just as big a role in the ecosystem of the ocean. Under the waves, they are not just a spiny star shaped meal; they are fast, focused hunters that never get full and almost always capture their prey. Sea stars come in many different shapes, sizes, and colors, but all stick to the same radially symmetrical body plan with the oral surface facing down, and the aboral surface facing up.

7: The diversity amongst sea stars is magnificent. They can exist as all colors of the rainbow, and can range from sizes of the 3mm wide Paddle Spine Sea Star or the massive Sunflower Sea Star that can grow up to 24 arms in some species and reach diameters of up to 1 meter. | Although not particularly terrestrial animals, sea stars can last extended periods of time out of water, but do not often seek the inhospitable conditions of dry land.

8: What IS a Sea Star? | A sea star's mod of transportation, its tube feet, are "hydraulically" powered by water from the water vascualr system. These hundreds of tube feet are good at not only for moving, but for griping food and surfaces. | There are many systems that make up a sea star, but what is unique about them is they each arm possesses an identical set of organs organized radially around the central disk. Because of this, if a sea star losses an arm, it can just regenerate it. Part of what has made sea stars so successful as an organism is their remarkable regenerative abilities.

9: FUN FACT: as long as a portion of the central disk in intact, a sea star can regenerate the rest of its body, as with this arm that appears to be growing a new sea star. | The Water Vascular System of a sea star is an essential, multi-purpose system. Not only does it power the tube feet that allow a sea star to move, it also functions as the waste management system. The journey starts at the Madreporite where water is taken in and travels down the stone canal. From there it enters the Ring canal where it is distributed to the Radial canals, Once in the Radial canal, it is sent to the Ampullae, which power the tube feet.

10: Where Are They Found? | Sea stars can be located at every corner, and every depth is the oceans. Part of their success is their ability to survive in any given condition. Sea stars can be found at the very edge of the shore in the tide pools, to the greatest depths visited by man, and even further. | While most sea stars exist in the mid oceanic range, some like this one prefer to live at greater depths.

12: Sea Star Cuisine | Sea stars are not picky eaters. They will devour just about anything that they come across, including shellfish, dying fish, marine plants, and event organic ooze that congeals on rocks on the ocean floor. Some sea stars, like the Sunflower Sea Star, will actively chase down their prey.What is truly fascinating is some of the techniques they have developed for eating their meals. While some prefer to engulf their prey whole, others have adapted an "easier" technique. They can spit out their stomachs, digest their food outside of their bodies, then suck up the remaining nutrients. | This sea star is demonstrating is ability to expel its pyloric stomach, so that it can digest large or difficult to reach food stuffs.

13: There is no limit to what sea stars will consume. These Sunflower Sea Stars are partaking in a community feast. What's on the menu? Decaying octopus. | In cases like this where it would take gratuitous amounts of energy to consume the prey, this clever sea star has a trick up its sleeve. It can pry open this unlucky bivalve just a tiny bit, then insert int stomach into its shell and begin digesting the mussel from the inside out.

14: Reproduction | Reproduction amongst sea stars can occur two ways. Asexual reproduction occurs when one sea star is cut in half, and then proceeds to regenerate into two separate sea stars. But in sexual reproduction, a male and female sea star release their gametes into the water and a fertilized egg is created, from there blastulazation takes place. It is said that echinoderms are the link between invertebrates and vertebrates because they develop as deuterostomes (anus first) like vertebrates, instead of as protostomes (mouth first). It is not long after fertilization that the zygote becomes a planktonic bipinnaria. | During gastrulazation, echinoderms develop the anus first instead of the mouth, showing that they are deuterostomes.

15: right: sea star after 71 days. left: sea star after 3 months | The bipinnaria is the basic larval stage of all echinoderms. THis is the one point in an echinoderm's life where it will travel the most, being helpless to the tides. Part of the geographic distribution of echinoderms has been fueled by this long distance travel.

16: Crown of Thorns, Living Menace | The Crown of Thorns Sea Star, Acanthaster planci, is the demonic result of human failure to understand sea star physiology. What was once a normal species has become a ravenous "destroyer of worlds" who's explosive population numbers have decimated miles of coral reef in the Australian Great Barrier Reef.

17: Gradually, as we over fished the Crown of Thorn's natural predator, Giant Triton, its population began to exponentially increase. Soon its numbers were so great that a single community could decimate and entire coral reef, leaving behind only the ghost white skeleton of a once vibrant paradise. Precaution and education of the local Australians and joint ventures between amature and professional marine biologist have proven successful in quelling some of the populations of C.oT., but this enemy is far from being defeated.

18: Our Impact on The Sea Stars | We as humans have found many uses for sea stars. We fish them up and dry them out for nifty beach nick nacks, eat them for food, or catch them to appreciate their beauty in a small home aquarium. In any case, it is not hard to recognize that we have had an effect of the sea star population. Although, because of their hardy nature and successful adaptations to every oceanic environment, we have had very little impact on the population as a whole. However, if we are not careful we can have very devastating effects on the sea star's environment, and on the sea star itself. In the event of an oil spill, sea stars can die off because oil clogs their madreporite and they cannot function. THis, and the war in the Great Barrier Reef and two extreme examples of what human hands can do to sea stars if we are not careful.

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  • By: Ryan H.
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  • Title: The Fascinating World of Asteroidea
  • a book about sea stars
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  • Published: over 8 years ago