Crustaceans

= = T h e W o r l d o f C r u s t a c e a n s                    **__Introduction__ ** Crustaceans form a very large group of Arthropods. They are invertebrates that have bilateral symmetry with an exoskeleton. They belong to the Domain: Eukaryota/Eukarya, Kingdom: Animalia, Subkingdom: Eumetazoa, Superphylum: Ecdysozoa, Phylum: Arthropoda , and Subphylum: Crustacea.

__Habitat__ Most crustaceans are free-living aquatic animals (animals that live in water for most or all of their lives), some live on land in moist places (they are believed to have evolved from the marine species), some are parasitic (hosts even include other crustaceans), and some are sessile.

**__Body Characteristics__ ** The body of a crustacean is composed of body segments, which are grouped into three regions. The first is the //cephalon // or head, the //thorax // or the mid-body //, //<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;"> and the //<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">pleon //<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;"> or abdomen. The cephalo and the thorax may be joined together to form a cephalothorax (the first major body section). The cephalothorax may be covered by one large carapace, which is a thick hard shell made of bone. Even though they are invertebrates, they have an exoskeleton (external framework), which protects the body. It may be thick or delicate. Various parts of the exoskeleton may be connected together. <span style="font-family: Georgia,serif; font-size: 16px; line-height: 23px;">The word arthropoda means "jointed foot". Arthropods use their appendages for movement, to capture pray, feeding, mating, and sensing their environment. Crustaceans have five pairs of legs. Lobsters and crabs belong to the crustacean group called Decapoda which means "ten legs". The first pair are claws that are used to catch and hold food. Whereas the other four pairs are used for movement. Crustaceans have one or two pairs of anntennae, which are used for sensing. They also have mandibles, which are used for crushing food.

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif; font-size: 22px; line-height: 19px;">__Crustacean Growth__



<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif; font-size: 17px;">Crustaceans cannot grow as many other animals do because of their outer skeleton. Instead they periodically shed the outer skeleton, grow fast for a short time, and then create another hard skeleton. Once the old shell has been discarded, it takes time for the new shell to harden. During this period, the animal is without its primary means of protection is vulnerable to attacks from predators such as trigger fish and the beak of the octopus. While this process is taking place they hide in an isolated place. However, they have an impressive group of weapons to use. The claw of many crustaceans is capable of exerting hundreds of pounds of pressure. Some even have the unique ability to produce a deafening miniature sonic boom with which they stun their prey. For example, the mantis shrimp can even break the glass of an aquarium or split a man's thumb to the bone with one strike. A remarkable ability that crustaceans have, is the ability to break off or to drop their appendages. This is called autonomy. They have special breaking-off points near the body. If caught, they can quickly break-off these appendages to escape. A new appendage can be grown easily. <span style="font-family: 'Times New Roman',Times,serif; font-size: 169%;"> __**Body Systems** 1) The Nervous System__



<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">The nervous system of crustaceans consists mainly of a brain connected to nerve centers. In primitive forms of crustaceans, the brain is connected to the eyes, antennules (small antennas), and a connecting ring around the esophagus which in turn is connected to the antennae. In more advanced forms of crustaceans, the antennae are directly connected to the brain.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 169%;">__2) The Digestive System__ <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">The digestive system of a crustacean is basically a gut or digestive tract. It is usually direct in its passage through the body. It begins with the foregut which is a simple tube in some species but very complex in others. In it's complex form, the foregut forms a gastric mill which consists of a series of ossicles (small bones like the one in the mid ear of humans) which move against each other by the force of powerful muscles that grind food. Between the foregut and the midgut, a filter of setae (stiff hairlike structures) blocks any food particles that are too big to go on until they are crushed by the gastric mill. The midgut is also different in different species of crustaceans but in general it has one or more pouches which are involved in various digestive processes. The hindgut is usually relatively short and is covered from the inside by cuticle (a protective and waxy or hard layer of tissue). The exit is controlled by a muscular anus.



<span style="font-family: 'Times New Roman',Times,serif; font-size: 169%;">__3) The Excretory System__ <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;"> There are only two different excretory organs found amid crustaceans, the antennal gland and the maxillary gland. Both have the same structure of a sac and a complicated duct that might pass through a bladder before opening outwards. In most adult crustaceans only one of the glands function at a time. The functions gland may change as the crustacean moves on through its life cycle.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 195%;">__4) The Circulatory System__ <span style="font-family: Helvetica,Times,serif; font-size: 12px; line-height: normal;"> <span style="font-family: 'Times New Roman',Times,serif; font-size: 17px; line-height: 25px;">As in other arthropods, the blood in crustaceans flows through channels without clearly stated walls. Some crustaceans have no heart, instead a blood pump, rhythmic movements of the body, gut, or appendages keep the blood flowing. However when there is a heart present, it is either surrounded with tissue or a membrane with openings. The positioning of the heart mainly depends on where the respiratory organs are located. The heart is usually in the cephalon, thorax, or abdomen.



<span style="font-family: 'Times New Roman',Times,serif; font-size: 169%;">__5) The Respiratory System__ <span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif; font-size: 130%;">In many small crustaceans there are no respiratory organs. CO2 and oxygen are exchanged directly through their tough outer layer. When gills are present, they are formed as modifications of parts of appendages.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 160%;">__6) Reproduction__ <span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif; font-size: 130%;">Most crustaceans have different sexes, and reproduce sexually. The eggs are produced in the ovaries in the female and are transported to the outside through oviducts. The sperms are produced in tubular testes in the male. After the eggs have been fertilized, they begin development and then hatch. When the eggs hatch, this can take several days or weeks depending on the species, the young larvae are broken off. From this point on, they are on their own and must eat, grow, swim, and survive. After a number of transformations, the larvae becomes a small adult. A small number of crustaceans are hermaphrodites, including barnacles, remipedes, and cephalacorida . Some may even change sex during a time in their life. Parthenogenesis is the only way in which crustaceans can reproduce asexually. In parthenogenesis, viable eggs are produced by a female without fertilization. This happens in many brachiopods, some ostracods, some isopods, and other crustaceans, such as the marmorkrebs crayfish.

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif; font-size: 169%;">__**Value of Crustaceans**__ <span style="font-family: 'Times New Roman',Times,serif; font-size: 169%;">__1) Importance__



<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">-Crustaceans are an important source of food for many animals. In many parts of the world, fisheries capture the larger species of crustaceans such as shrimp, lobsters, and crabs since some humans consider them as food delicacies. <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%; line-height: 19px;">Humans consume a large amount of crustaceans such as cab, shrimp, prawns, and crayfish. Crustaceans are high in nutrients, and are therefore an important part of a human's diet. The water flea and the brine shrimp are also ued as food in aquariums. <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">-In Japan, barnacles are allowed to settle on bamboo stakes so that they can later scrape them off and use them for fertilizer. -Microscopic species of crustaceans may be found in groups so large that they change the color of the sea. This indicates fishermen where groups of herring or mackerel may be found. -Ostracod fossils, of which many can be found, are important for geologists and oil prospectors. -In most parts of America, crayfish (especially the soft-shelled individuals, are use by many fishermen as bait. -Prawn fishery, which means capturing as well as culturing prawns, has advanced in many countries including Pakistan.

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif; font-size: 169%;">__2) Disadvantages__

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif; font-size: 130%;">-Much damage can be done to rice fields by crustaceans. Burrowing crabs and the mud-eating, shrimp like //Thalassina// of Malaya (a former country of South-East Asia) mainly cause this damage. They make the fields leak, thus the roots are exposed to the sun. If the fields are near the sea, salt water may seep into the fields. Tadpole shrimps are usually found in rice fields. They mix up in the fine silt when searching for food doing so killing many of the plants. -Land crabs and crayfish might ruin tomato and cotton crops.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 218.4%;">__Fun Facts__ <span style="font-family: 'Times New Roman',Times,serif; font-size: 140%;">- The largest kind of crustacean, the giant spider crab of Japan, measures up to 12 feet (3.7 meters) across between its outstretched claws. -The smallest crustaceans, such as water fleas, can be smaller than 1⁄125 inch (0.2 millimeter) long. <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">- Why are they called fiddler crabs? Male fiddler crabs have one large claw, which they wave in the air to impress females and intimidate other males. It looks as if the male is playing a fiddle, or a violin. -Some species of shrimp are luminescent, meaning they produce a faint light. - Lobsters listen with their legs and taste with their feet. Plus, their teeth are in their stomach, and their kidneys are in their head. -Lobsters come in every color but red. They can be blue, light yellow, greenish-brown, grey, dusty orange, calico, and may even have spots! They all turn red when cooked, however. -How times have changed! While lobsters today are considered a delicacy, in Colonial times they were considered "poor man's food" and were only fed to children, servants, and prisoners. __**<span style="background-color: #ffffff; display: block; font-family: 'Times New Roman',Times,serif; font-size: 195%; font-weight: normal; text-align: left;"> Examples of Crustaceans **__

<span style="display: block; font-family: 'Times New Roman',Times,serif; font-size: 130%; text-align: left;"> <span style="font-family: Georgia,serif;">Examples of crustaceans includes crabs, lobsters, crayfish, shrimp, krill, barnacles, and wood lice.

<span style="display: block; font-family: Georgia,serif; font-size: 219.7%; text-align: left;">__Sources__ <span style="font-family: 'Times New Roman',Times,serif; font-size: 132%;">Source One: http://en.wikipedia.org/wiki/Crustacean Source Two: Animal Diversity- Reference Source Three: [] Source Four: [] Source Five: <span style="font-family: 'Times New Roman',Times,serif; font-size: 132%; line-height: normal;">" <span style="font-family: 'Times New Roman',Times,serif; font-size: 110%; line-height: normal;">**<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">crustacean ." //Encyclopædia Britannica. //Encyclopædia Britannica Online<span style="font-family: arial,helvetica,sans-serif; line-height: 19px;">. Encyclopædia Britannica, 2010. Web. 20 Apr. 2010 <span style="font-family: 'Times New Roman',Times,serif; line-height: normal; white-space: nowrap;"><[|http://www.search.eb.com/eb/article-33807]>. <span style="font-family: 'Times New Roman',Times,serif; font-weight: normal;">Source Six: <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; line-height: normal; white-space: normal;">//<span style="font-family: 'Times New Roman',Times,serif;">krill // <span style="font-family: 'Times New Roman',Times,serif;">. Photograph. <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; line-height: normal; white-space: normal;">//<span style="font-family: 'Times New Roman',Times,serif;">Encyclopædia Britannica Online // <span style="font-family: 'Times New Roman',Times,serif;">. Web. 20 Apr. 2010 < <span class="articleUrl" style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; line-height: normal; white-space: nowrap;"><span style="font-family: 'Times New Roman',Times,serif;">[|http://www.search.eb.com/eb/art-76472] <span style="font-family: 'Times New Roman',Times,serif;">>. Source Seven: <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; line-height: normal; white-space: normal;">//<span style="font-family: 'Times New Roman',Times,serif;">crustacean // <span style="font-family: 'Times New Roman',Times,serif;">. Photograph. <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; line-height: normal; white-space: normal;">//<span style="font-family: 'Times New Roman',Times,serif;">Encyclopædia Britannica Online // <span style="font-family: 'Times New Roman',Times,serif;">. Web. 20 Apr. 2010 < <span class="articleUrl" style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; line-height: normal; white-space: nowrap;"><span style="font-family: 'Times New Roman',Times,serif;">[|http://www.search.eb.com/eb/art-104965] <span style="font-family: 'Times New Roman',Times,serif;">>. Source Eight: http://animaldiversity.ummz.umich.edu/site/resources/biodidac/crus003b.gif/medium.jpg <span style="font-family: 'Times New Roman',Times,serif; font-weight: normal;">Source Nine: <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px;">//<span style="font-family: 'Times New Roman',Times,serif;">shrimp // <span style="font-family: 'Times New Roman',Times,serif;">. Photograph. <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px;">//<span style="font-family: 'Times New Roman',Times,serif;">Encyclopædia Britannica Online // <span style="font-family: 'Times New Roman',Times,serif;">. Web. 20 Apr. 2010 < <span class="articleUrl" style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; white-space: nowrap;"><span style="font-family: 'Times New Roman',Times,serif;">[|http://www.search.eb.com/eb/art-124890] <span style="font-family: 'Times New Roman',Times,serif;">>. <span style="font-family: 'Times New Roman',Times,serif; font-weight: normal;">Source Ten: <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px;">//<span style="font-family: 'Times New Roman',Times,serif;">American lobster // <span style="font-family: 'Times New Roman',Times,serif;">. Photograph. <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px;">//<span style="font-family: 'Times New Roman',Times,serif;">Encyclopædia Britannica Online // <span style="font-family: 'Times New Roman',Times,serif;">. Web. 20 Apr. 2010 < <span class="articleUrl" style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; white-space: nowrap;"><span style="font-family: 'Times New Roman',Times,serif;">[|http://www.search.eb.com/eb/art-24012] <span style="font-family: 'Times New Roman',Times,serif; font-size: 13px; font-weight: normal; white-space: nowrap;">>. Source Eleven: <span class="articleUrl" style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; white-space: nowrap;"> //<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%; font-weight: normal;">claw // <span style="font-family: 'Times New Roman',Times,serif; font-size: 13px; font-weight: normal; white-space: normal;">. Photograph. <span style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; white-space: normal;">//<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%; font-weight: normal;">Encyclopædia Britannica Online // <span style="font-family: 'Times New Roman',Times,serif; font-size: 13px; font-weight: normal; white-space: normal;">. Web. 20 Apr. 2010 <span style="font-family: 'Times New Roman',Times,serif; font-size: 13px; font-weight: normal; white-space: nowrap;">< <span class="articleUrl" style="font-family: 'Britannica Unicode Sans Roman','Trebuchet MS',Trebuchet,Arial,Geneva,sans-serif; font-size: 10px; white-space: nowrap;"><span style="font-family: 'Times New Roman',Times,serif; font-size: 130%; font-weight: normal;">[|http://www.search.eb.com/eb/art-124892] <span style="font-family: 'Times New Roman',Times,serif; font-size: 13px; font-weight: normal; white-space: nowrap;">>. ** <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Source Twelve:www.seasky.org/reeflife/sea2e.html Source Thirteen: http://uh.edu/engines/lobsteranatomy.jpg Source Fourteen: http://photography.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Photography/Images/POD/r/rice-fields-154515-lw.jpg Source Fifteen: http://s1.hubimg.com/u/558168_f520.jpg Source Sixteen: http://www.kwic.com/~pagodavista/schoolhouse/species/insects/pics/cryfsant.jpg Source Seventeen: http://news.nationalgeographic.com/news/2007/02/photogalleries/antarctic-species/images/primary/crustacean_big.jpg Source Eighteen: <span style="color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 108%;">http://animals.howstuffworks.com/marine-life/crustacean-info6.htm <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">Source Ninetenn:http://www.redlobster.com/press/media_kit/lobsterfacts.asp Source Twenty: http://arthropods-grade7.wikispaces.com/ Source Twenty-One: http://www.petinsurance.com/healthzone/pet-horoscopes/~/media/All%20PHZ%20Images/Pet%20Horoscopes/crustacean.ashx


 * ** Extra Questions: ** ||
 * ** 1. What is the function of the swimmerets? ** ||
 * ** 2. Are crustaceans harmful to humans &/or crops? Explain. ** ||

<span style="font-family: 'Times New Roman',Times,serif; font-size: 17px; line-height: 25px;">__Answer to Question 1:__



<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">In the abdomen area of crustaceans there are five pairs of appendages called swimmerets. Swimmerets aid the crustacean in movement, are essential for reproduction, and direct water over the feathery gills where carbon dioxide is exchanged for oxygen.

__Answer to Question 2:__ -Much damage can be done to rice fields by crustaceans. Burrowing crabs and the mud-eating, shrimp like //<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">Thalassina //<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;"> of Malaya (a former country of South-East Asia) mainly cause this damage. They make the fields leak, thus the roots are exposed to the sun. If the fields are near the sea, salt water may seep into the fields. Tadpole shrimps are usually found in rice fields. They mix up in the fine silt when searching for food doing so killing many of the plants. -Land crabs and crayfish may ruin tomato and cotton crops.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 117%;"> -George Jarrouj -Hannah Milad ​ -Christian-Paul Nemer -Harry Simitian
 * __By:__** - Christina-Maria Cavalcanti