Senses. complex sensory system called the ampullae of Lorenzini in their head. At ranges of a few feet, sharks can actually feel

Transcription

1 NINATIONAL OCEANIC AND ATMOSPHERIC ADMI Test Your Knowledge! Across 2. A favorite food of the smooth dogfish. 4. This species of dogfish shark was commonly used in fish ʼn chips in England. 9. Many sharks exhibit this color scheme dark on top and lighter on the bottom. 11. A shark smells with these organs. 12. A shark species that can live for extended periods in fresh water. 13. Used in reproduction, they are located between the pelvic fins of the male shark. 14. These fins give the shark lift when swimming Down 1. A sharkʼs skeleton is made of this flexible material. 3. This opening, near the smooth dogfishʼs eye, provides oxygen to the eyes and brain. 5. The name of the tiny tooth-like scales on a sharkʼs skin. 6. Sharks have this kind of tail, which has a larger upper lobe and a smaller lower lobe. 7. Another name for a sharkʼs tail fin. 8. This is the large organ that gives the shark some buoyancy. 10. If a shark does not keep swimming, it will do this. Check your answers at the bottom of the page! 1 lack of a swim bladder. The paired pectoral fins provide lift like the wings of an airplane. The pelvic fins, fixed in an upward position, also provide lift. The unpaired dorsal and anal fins act as stabilizers, preventing the shark from rolling in the water. The caudal or tail fin gives the smooth dogfish its swimming power. The upper lobe of the tail balances the pelvic fin by pushing down, helping the shark to glide through the water. A shark can swim only forward and not backward like other fish can. Senses Smooth dogfish have well-developed sensory organs. Their eyes are among the most efficient in the animal kingdom, allowing them to see in the darkest of waters. Their eyes contain a mirror-like, reflective layer called the tapetum lucidum, which enhances night vision. A shark s nostrils can smell a drop of blood in a million gallons of water! Sharks also detect prey by sound. In addition to an inner ear, they have a lateral line system that detects vibrations. It consists of a series of fluid-filled canals that lie just beneath the skin on the shark s head and along its sides. Special cells in these canals sense changes in pressure, so that any disturbance in the water that sends out waves, like a struggling fish, is felt by the shark. Sharks also have one unique sense electroreception thanks to a complex sensory system called the ampullae of Lorenzini in their head. At ranges of a few feet, sharks can actually feel The colored dots highlight the location of the ampullae of Lorenzini, electroreceptors that can detect the electricity generated by another fish. the electricity generated by another fish. Some sharks, like hammerheads, use electroreception to locate stingrays buried in the sand. For Further Exploration The Bridge: Sea Grant Ocean Sciences Education Center. Sharks, Skates, and Rays. Castro, José I On the Origins of the Spanish Word Tiburón and the English Word Shark. Environmental Biology of Fishes 65: Florida Museum of Natural History. International Shark Attack File. NOAA Fisheries.Shark Web Site. ReefQuest Centre for Shark Research. Biology of Sharks and Rays. Sea World. Sharks and Their Relatives. infobooks/sharks&rays/home.html World Fish Center. FishBase: A Global Information System on Fishes. U.S. DEPARTMENT OF COMMERCE The Delaware Sea Grant College Program is a member of a national network of universities committed to research, education, and technology transfer designed to meet the changing needs of our ocean, coastal, and Great Lakes regions. The program is funded by the National Oceanic and Atmospheric Administration in the U.S. Commerce Dept.; the State of Delaware; and the University of Delaware. This publication was produced by the Delaware Sea Grant Marine Advisory Service in cooperation with the UD Office of Public Relations, Research Communications Initiative. Dr. William Hall and Tracey Bryant, writers/editors; David Barczak, art director; and Pamela Donnelly, production manager. Special thanks to The College School at the University of Delaware and East Millsboro Elementary School for their assistance with the pilot-testing of this educational publication. For more information, contact UD Marine Public Education, 222 S. Chapel Street, Newark, DE Phone: (302) MarineCom@udel.edu. For other Delaware Sea Grant publications, visit STRATION Meeting the Science Standards Here are a few examples of how K 12 educators can use the Dogfish Shark Model to teach the fundamental concepts and principles set forth in the National Science Education Standards: Standard: Unifying Concepts & Processes in Science Evolution; organization and taxonomy. Standard: Science as Inquiry Use of the model to extend the senses and make valid observations. Standard: Physical Science Forces of motion involved in swimming. Standard: Life Science Anatomical structure and function; reproduction and life cycles. Standard: Earth & Space Science Earth history; fossils provide important evidence of life and environmental changes over time. Standard: Science & Technology Technological developments as a result of products derived from sharks; e.g., medicines, liver oils, shark skin leather, and chondroitin. Standard: Science in Personal & Social Perspectives Population status of sharks; medical applications; and sharks and humans. Standard: History & Nature of Science Medical applications; human use of sharks through history; and ecological role of sharks in nature. Crossword Answers: Across 2. lobster, 4. spiny, 9. countershading, 11. nares, 12. bull, 13. claspers, 14. pelvic Crossword Answers: Down 1. cartilage, 3. spiracle, 5. denticles, 6. heterocercal, 7. caudal, 8. liver, 10. sink 9/06:10K

2 NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION U.S. DEPARTMENT OF COMMERCE 3-D MODEL Assembly Time: 30 mins. Fun and educational for all ages! Did you know? A sharkʼs skin even has teeth! A shark must keep swimming or it will sink. More people die each year from bee stings than from shark attacks. Meets the National Science Education Standards

3 Welcome to the world of sharks! This publication is designed to introduce you to these awesome creatures by giving you an in-depth look at one of the most common sharks along the U.S. Atlantic coast the smooth dogfish. On the next pages, youʼll find the parts and instructions for making your own 3-D shark model, as well as lots of interesting information to explore. Fascinating and fearsome, sharks are the ocean s great hunters. Most are built for speed and equipped with strong jaws and teeth to catch and hold prey. With few natural predators to eat them, most large sharks are at the top of the ocean s food chain. They help keep populations of other large fish in check that otherwise would deplete stocks of smaller fish and throw the ecosystem out of balance. Thus, sharks play an important role in maintaining the ocean s delicate food web. Sharks live in ocean waters around the globe, from shallow bays to the deep sea. Some coastal species, such as the smooth dogfish, travel to the food-rich, less salty waters of estuaries such as the Delaware Bay to bear their young. A few species, such as bull sharks and speartooth sharks, have special adaptations that enable them to live for a period of time in the fresh water of rivers and lakes. Bull sharks have been recorded more than 1,700 miles up the Mississippi River and over 2,100 miles upstream in the Amazon River. While many people picture sharks as man-eaters, the truth is that over 80% of the world s 375-plus species of sharks are less than 5 feet long. The world s smallest sharks, the dwarf lanternfish and the pygmy ribbontail catshark, are only 6 to 7 inches in length. That s about as long as a ballpoint pen! Did you notice that we say there are 375-plus species of sharks? That s because every few years a new shark species is discovered. In fact, ichthyologists (fish scientists) have pictures of new species of sharks from the deep ocean that have not been named yet because no one has been able to catch them for examination. Snout Eye A Closer Look at Sharks How are sharks different from other fish? Here are three key differences to keep in mind as you examine the external anatomy of the smooth dogfish shark below. A shark is shaped much like a jet fighter. It has fixed fins, which means the fins do not move. The pectoral and pelvic fins lift the shark, the caudal or tail fin helps propel the shark forward, and the dorsal and anal fins help prevent the shark from rolling as it swims. First Dorsal Fin Spiracle This opening provides oxygen directly to the eyes and brain. A shark s skin has tiny tooth-like scales called dermal denticles. Furniture makers once used dried shark skin, called shagreen, as a fine-grade sandpaper. Japanese Samurai wrapped their sword handles with shark skin to improve their grip. Sharks have a heterocercal (pronounced hetero-circle ) tail. That means the two sections or lobes of the tail are of unequal length. The larger upper lobe balances the pectoral and pelvic fins by pushing down, propelling the shark through the water. Smooth Dogfish Shark (Mustelus canis) Lateral Line This series of fluid-filled canals, just under the skin on a shark s sides, detects vibrations in the water, helping a shark to hear. Second Dorsal Fin Caudal Fin (Upper lobe) Mouth Nares The shark smells through two nostrils called nares on the underside of the snout. Pectoral Fin Gill Slits The gills take up oxygen from the Pelvic Fin water, enabling the shark to breathe. A shark s length is measured from the tip of its snout to the end of its tail. Claspers (males only) Located between the pelvic fins of the male shark, they are used in reproduction to transfer sperm to the female. Anal Fin Caudal Fin (Lower lobe) Inside the belly of the beast... Unlike most fish, a shark does not have a swim bladder to help it stay afloat, so a shark must keep swimming or it will sink. The shark s large liver acts like a life preserver, helping the animal to maintain some buoyancy in the water. The liver stores oils and fats, which are lighter than water. The liver can account for up to 25% of a shark s weight. Blending in... Many sharks are dark-colored on the top or dorsal side of their body, and lighter-colored underneath on the ventral side. This color scheme is called countershading. It helps hide the shark from potential prey. A fish looking down will not easily see a shark because the shark s surface will blend in with the dark seafloor. Conversely, a fish looking up from the seafloor toward the sunlit surface waters will not easily see a shark s light underside. Sharks have dominated the ocean for over 400 million years, yet today s sharks still look a lot like their ancestors. At left is an artist s representation of the ancient shark Megalodon. With an estimated length of at least 40 feet, this shark was longer than a school bus. Its teeth were as big as a human hand! Megalodon means giant tooth. Megalodon illustration by Todd Marshall; tooth courtesy of Delaware Geological Survey Make no bones about it... A sharkʼs skeleton contains no bones. Itʼs made entirely of a tough, flexible tissue called cartilage. Question: Can you name at least two parts of the human body that contain cartilage? Check your answer below! Answer:Cartilage is found in a lot of places in your body including your ears, nose, throat, joints, and the disks between the vertebrae in your spine. There are over 375 species of sharks. Eighty percent of the worldʼs sharks are not dangerous to people.

4 People and Sharks No other animal is as feared as the shark, probably because we feel we are at its mercy when we are in the ocean. We all feel there might be a shark out there waiting for us... Nothing could be further from the truth, however, as fatal shark attacks are extremely rare. You do the math. Take the world s population of 6.5 billion people and divide it by 6 fatal shark attacks a year. That s how likely it is that you will be killed by a shark. The reality is that populations of sharks are declining worldwide at an alarming rate as millions of sharks are killed every year for food, fertilizer, and other products. Sharks are an important source of food. Fish and chips, the original fast food, had its beginnings in factories in England during the Industrial Revolution. The featured fish in this popular dish was, and still is, the spiny dogfish shark. Today, one of the most expensive meals in an Asian restaurant is shark fin soup, sometimes costing over $700 a bowl. While shark finning is banned in U.S. waters, many countries still allow this practice in which the fins are cut off a live shark, and then the shark is thrown back into the sea to die a gruesome death. In earlier times, shark skin, with its tiny teeth (dermal denticles), was used by woodworkers as a fine-grade sandpaper to make furniture. Japanese Samurai warriors and German soldiers wrapped the skin of sharks and their relatives, the skates and rays, around their sword handles to prevent them from slipping out of their hands. American Indians in Florida used sharks teeth for arrowheads, while Pacific islanders used them as barbs in their war clubs. Today, fine leathers made from shark skin are used to craft shoes and other accessories, and sharks teeth are used in jewelry. Sharks are used to teach anatomy through classroom dissection. They also are important in medical research because of their incredible immune system, which makes them highly resistant to cancer and other diseases. Shark liver oil has been used to make squalene, a product sold as a cure-all in health food stores. Currently, shark cartilage, often labeled as chondroitin, is sold in tablet form to relieve joint pain. Many of these products have not been documented to be effective. Be sure to read this entire publication before assembling your shark model. Youʼll need all the information to solve the puzzle on the back page! Teachers, you may want to photocopy this page for your classroom bulletin board! The worldʼs largest shark (and fish) is the 14-meter-long (46 ft.) whale shark. This gentle giant feeds on plankton.

5 Snout The snout is taped together during the last step in assembling your model. Top Dorsal Fin Mountain Fold Valley Fold Su Sc St the rem St the St 3 1 Belly This is where the dorsal side of the pectoral fin is attached Side 1 The Top will overlay this section, completely covering the white area. Helpful Hint: Be sure to read all of the instructions before you start! Dorsal Fin Step 6

6 Build Your Own Dogfish Shark Step 4 Supplies You Will Need: Scissors and clear tape. Step 1. Separate the model from the rest of the document by carefully removing the staples. Step 2. Next, cut out your shark, following the solid black line around the body and pectoral fin. Step 3. With the dark blue underside facing you, begin to mountain-fold (see above left) along the green dashed lines and valley-fold along the white dotted lines. Step 3 Step 4. Now you are ready to begin taping the parts together. With the shark s belly facing down, pull up Side 1. Then start matching up and taping together the numbered parts, starting with 1 and 1, then 2 and 2, and 3 and 3. Next, match up and tape together Step 5 the dorsal fin, second dorsal fin, and caudal fin. Step 5. On the shark s belly side, tuck the tab extending from behind the pelvic fin up into the shark s body and tape securely. Second Dorsal Fin Flap Claspers Caudal Fin Pelvic Fin Pelvic Fin These flaps are folded, tucked up into the shark s body, and then taped into position. Ventral Side of Pectoral Fin Caudal Fin Second Dorsal Fin Align and tape both sides of the second dorsal fin and caudal fin together. 6 Step 6. Apply a piece of rolled-up tape to the dorsal side of pectoral fin where indicated and attach the fin to the shark s belly. Step 7 Step 7. Last, tape the parts of the shark s snout together. Hot diggity dogfish! Your shark model is now complete!

7 Geographically Speaking Approximately 108 species of sharks are found in U.S. waters. One of the most common sharks along our Atlantic coast is the subject of this model: the smooth dogfish, often called the sand shark. While sharks are marine fishes that live in the ocean, some sharks, including the smooth dogfish, have the ability to survive in the less salty waters found in estuaries such as the Delaware Bay for extended periods of time to feed and to give birth to their pups. A shark is called a pup up until its first year of age. In fact, this model is representative of a female smooth dogfish pup. The pups range from 12 to 15 inches long at birth. A typical brood contains 10 to 20 pups. Dorsal Side of Pectoral Fin Place tape here. Sharks live all over the world, from warm, tropical lagoons to polar seas. Some sharks can even live in freshwater lakes and rivers for a period of time! The smallest shark is the dwarf lantern shark at 15 cm (6 in). How much shorter is it than this page?

8 Smooth Dogfish Taxonomy Now it s time to introduce you to the hound of the sea the smooth dogfish, one of the most common sharks found along the western Atlantic coast. This small, gray shark, averaging 3 to 5 feet in length, is harmless to humans. In fact, in many instances, it has given its life for us! In Europe, it is esteemed as a food fish, while here in the United States, it has been a popular animal for dissection in biology and zoology classrooms. The smooth dogfish prefers bays and nearshore waters with depths of 18 meters (60 feet) or less. It ranges from Massachusetts to Venezuela, and along southern Brazil. It is absent from most of Brazil except the southern region because it prefers moderate rather than tropical temperatures. Smooth dogfish migrate seasonally, following the warmer water temperature and more plentiful food south along the U.S. east coast in the winter and then traveling back north in the summer. A nocturnal species, this shark typically hunts at night in small schools, or packs, just as wild dogs would. Like all sharks, the smooth dogfish has a sleek body, tiny toothlike scales called dermal denticles, and fixed (immovable) fins. However, it also has unique features that distinguish it from other sharks. The smooth dogfish s range is from Massachusetts to Venezuela, and along southern Brazil. The smooth dogfish does not have the sharp, pointed teeth associated with many sharks. Rather, it has hundreds of small, flat, pavement-like teeth that are used for crushing and grinding its prey. Crabs, shrimp, and lobsters are among its favorite foods. An opportunistic feeder and a scavenger, it also will eat fish, squid, clams, and worms. Another special characteristic is its camoflauging ability. It can slowly deepen or lighten the shade of its skin to match its surroundings. The smooth dogfish s skin contains pigment cells called melanophores, which contract to deepen its color, or relax to lighten it. Its color may range from bluish gray to olive-brown on the dorsal side, and from white to yellow on the ventral side. Size and Reproduction Smooth dogfish males are smaller than the females. Males generally average 3 feet long, mature at two or three years of age, and may live to be as old as 10. Females are about a third larger than the males, growing to a maximum length of 5 feet. The females mature in four to seven years and may live to 16 years of age. A female will give birth to 10 to 20 young after a 10- month gestation period. The pups are inches long at birth and are ready to hunt as soon as they are born. Swimming Like all sharks, smooth dogfish have a skeleton made of cartilage, not bone. This makes for a light, yet strong, flexible skeleton that makes swimming both easier and faster. Kingdom: Animalia Phylum: Chordata (has backbone or notochord) Subphylum: Vertebrata (has flexible internal skeleton; brain encased in cranium) Class: Chondrichthyes (cartilaginous fishes) Sub-Class: Elasmobranchii (sharks and rays) Order: Carchariniformes Family: Triakidae (houndsharks). There are 36 species worldwide; 7 in the United States, and 2 on the U.S. Atlantic coast. Genus: Mustelus (Latin meaning weasel-like ) Species: canis (Latin meaning dog ) Closest Relatives: While the smooth dogfish is harmless to humans, it is closely related to the requiem sharks, which include many of the world s deadliest species, including tiger and bull sharks. Where Did the Word Shark Come from? Today, the word shark is commonly used in English, and the word tiburón is used in Spanish.Yet centuries ago, neither the Spanish nor the English had a word for a large shark in their language because they had never seen one before. When they went fishing, it was in rivers or in the sea close to shore. Around 1500, when they began exploring the New World, the Spanish saw large sharks for the first time and adopted the word tiburón from the Carib Indians ti for ground, and buron for fish. Later, when the English arrived, they used tiburón briefly but then adopted the word sharke, which was in full use by the 1700s. Sharke or shark appears to have originated from the Mayan word xoc, which sailors corrupted to shark over time. However, sharks do not have a swim bladder, the air-filled sac that helps keep the bony fish (fish with skeletons made of bone) afloat. Yet buoyancy is not a problem because of the shark s lightweight skeleton and its large liver. The liver acts a bit like a life preserver, helping the shark to maintain some buoyancy. The liver stores oil and fats, which are lighter than water. However, when a hungry shark has used up its fat and oil reserves, it must swim harder or it will sink. When tired, smooth dogfish have been observed resting on the seafloor. The smooth dogfish s rigid fins and heterocercal tail (a tail with two lobes of uneven length) also compensate for the A Lesson from the Tooth Fairy Sharks do not all have the same kind of teeth. As shown at far right, the smooth dogfish has short, blunt pavement-like rows of teeth, which it uses to grind up crustaceans crabs, shrimp, lobsters, and other prey. Other sharks, such as the tiger shark, have sharp, pointed teeth for catching, holding, and tearing the flesh from prey. Their teeth grow in rows as if on a conveyor belt. When a tooth breaks off, a new one replaces it. Sharks can shed thousands of teeth over a lifetime. Some species replace their front teeth every two weeks! Tiger Shark 10-Year-Old Smooth Dogfish Tooth Human Tooth Teeth Teeth are shown at actual size. Like wild dogs, dogfish sharks travel in packs. These harmless sea hounds feed mainly on crustaceans.