SHARK WEEK

1. SHARK WEEK http://www.youtube.com/watch?v=UruXWui1EG8

2. Discovery Channel Shark Week • http://dsc.discovery.com/sharks/shark-o-nator • Resource site

3. Shark Myths • http://www.mote.org/index.php?engine_id=&src=search&search_id=search_new&search_this=shark+myth • Resource site • http://www.sharks-world.com/facts_about_sharks.html

4. #1 • Sharks prefer human blood. • False! Most sharks don't appear to be especially interested in the blood of mammals as opposed to fish blood

5. #2 • Sharks have peanut-sized brains and are incapable of learning. • Sharks' relatively large and complex brains are comparable in size to those of supposedly more advanced animals like mammals and birds. Sharks also can be trained

6. #3 • All sharks have to swim constantly • Misconceived! Some sharks can respire by pumping water over their gills through opening and closing their mouths while at rest on the bottom.

7. #4 • Sharks have poor vision. • Erroneous! Sharks' eyes, which are equipped to distinguish colors, employ a lens up to seven times as powerful as a human's.

8. #5 • Sharks are not found in freshwater. • Forget it! A specialized osmoregulatory system enables the bull shark to cope with dramatic changes in salinity -- from the freshwaters of some rivers to the highly saline waters of the ocean.

9. #6 • Whale sharks, the largest species of shark, are voracious predators • Whale sharks, which are the largest fish that have ever lived, are plankton feeders like the great whales, thus the name.

10. Seaworld: sharks • http://www.seaworld.org/infobooks/Sharks&Rays/home.html

11. What are Sharks? • Vertebrates • Cartilage skeletons • 350 species • Can live for 20-30 years • Five gill openings on each side of head • Scales called “denticles” make skin feel rough • Scales do not grow larger. Shark grows more of them. Scales cannot be used to tell the age of the shark

12. Denticles of a great white shark

13. Cont…… • Some are solitary hunters. Others, hunt in groups • Found in all oceans at all depths- most prevalent in tropical, coastal waters • Primarily marine, but do travel up the mouths of rivers into freshwater in some species • Many are carnivorous, some planktonic • Most powerful jaws on the planet

14. Ancient Sharks • The most common shark fossils are teeth because sharks, unlike most other animals, can lose many thousands of teeth during their lives • Shark skeletons are not made of bone- therefore, whole skeletons are only found where the animal was quickly covered with mud and remained undisturbed • Oldest shark fossil-More than 400 million years old. 150 million years since evidence of evolution

16. megalodon • http://www.youtube.com/watch?v=Spo8vkrJFRo

17. Taxonomy • 460 different species • 8 orders • Hexanchiformes-six gilled and seven gilled sharks • Squaliformes- dogfish sharks • Pristiophoriformes- sawsharks • Squatiniformes- angel sharks • Heterodontiformes- bullhead sharks • Orectolobiformes- carpetsharks • Lamniformes- mackerel sharks • Carcharinoformes- hammerhead and requiem sharks

19. 25 species of sharks reside in the gulf of Mexico

20. Let’s get acquainted: Shark Anatomy • Sharks typically have a fusiform body (rounded and tapering at both ends). This body shape reduces drag and requires a minimum of energy to swim • No swim bladder. Tends to sink. Has oil in liver to increase buoyancy • 5 gill slits • Caudal fin is well developed and powerful • Tail is heterocercal- upper lobe is longer than the lower lobe • Powerful jaws with sharp teeth

21. fins • Sharks have five different types of fins. • a. Paired pectoral fins lift the shark as it swims. • b. Paired pelvic fins stabilize the shark. • c. One or two dorsal fins stabilize the shark. In some species, dorsal fins have spines. • d. A single anal fin provides stability in species where it is present; not all sharks have an anal fin. • e. The caudal fin propels the shark.

22. fins

23. Tails/Swimming • The ability to pump water over gills (buccal pumping) varies between shark species • Less active sharks have an increased ability for buccal pumping • More active pelagic sharks use ram ventilation, meaning they ventilate the gills by holding the mouth open while swimming • Some sharks are obligate ram ventilators, meaning they have to keep constant forward motion in order to continue respiration

24. Teeth • Each type has a different shaped tooth • 20,000 teeth per lifetime • Arranged in parallel rows • Studies have shown that an average nurse shark will replace each front row tooth every ten days to two weeks in summer when actively feeding and every one to two months when they are less active in the winter

25. Sharks never run out of teeth.  If one is lost, another spins forward from the rows and rows of backup teeth

26. Colors and Camouflage • Countershading • Dorsal side is darker than the ventral side

27. Breathing • Most sharks swim continuously because the opening and closing of the mouth forces water through the mouth, over the gills, and out through the gill slits • When caught in fishing nets, sharks cannot swim to force the water in and therefore “drown” • Not all sharks need to swim for gas exchange. Nurse sharks rest on the bottom because they force water over their gills by opening and closing their mouth

28. spiracles • behind the eyes at the top of the head. These openings bring oxygen-carrying water into the gill chamber. Spiracles originate from rudimentary first gill slits and are reduced or absent in active, fast-swimming sharks.

29. Ramjet Principle

30. Shark Senses • Sharks have six highly refined senses: smell, hearing, touch, taste, sight, and electromagnetism

31. Incredible Senses • In addition to the lateral line, sharks have a sensory organ called the Organ of Lorenzini; this organ is used to detect electrical currents when sharks are close to an object (the movement of muscles – even those used in respiration – emit a small electrical charge) – this allows sharks to detect living prey even it is hidden from their view if they can get within a few feet of the organism • “built in compass”

32. Incredible Senses • Lateral Line • The lateral line, together with the ampullae of Lorenzini comprise the electrosensory component of the sharks sensory system. The lateral line allows the shark to orient to particle movement or sound. It consists of structures called neuromasts which are located in canals that lie just below the surface of the skin or the scales. Similar to the ampullae of Lorenzini there are pores that open to the outside and movement caused by prey can be detcted by the neuromasts.

33. Shark lateral line

34. Incredible Senses Cont….. • Hearing- • Ears are internal, not external • Ears: 3 semi-circular canals that resemble those in the ears of other vertebrates • Sharks can hear noises from over 700 feet away • Vibrations in the water are heard as sound

35. Incredible Senses • Eyes • Sharks have a nearly 360-degree visual field • Some sharks have a third eyelid, called the nicitating membrane, which protects the exposed portion of the eye during feeding or object contact • The great white shark does not have a nicitating membrane, and instead rolls the eye back into its orbit to protect it during feeding • Most sharks have a reflective layer in the back of the eye called a tapetumlucidum which boosts the sensitivity of the eye in dim light • A juvenile lemon shark has a lens with 7 times the optical power of a human lens • Humans focus by changing the shape of the lens; sharks focus by changing the position of the lens by moving it toward or away from the retina

36. Incredible Senses • Nostrils- used only for smelling. NOT breathing • Seawater flows over the nostrils bringing chemical clues as to what’s nearby • Sharks can detect tiny amounts of blood from more than 1 mile away. • The hungrier the shark gets, the sharper its sense of smell. Scent makes them aggressive- “feeding frenzy”

37. Shark Senses • http://www.youtube.com/watch?v=h1XYa93Rz_Q

38. osmoregulation • Shark Osmoregulation Facts: • Sharks use high concentrations of body urea to help osmoregulate • Sharks living in salt water must balance the influx of NaCl (salt) into the body by excretory mechanisms in the rectal gland, kidney and gills • Sharks living in dilute salinity or freshwater conditions must balance the influx of water into the body by increasing urinary water excretion and increasing salt uptake through the gills • 90% of the secretion of body acids/bases into the water in order to balance internal pH is done by the gills

39. http://www.youtube.com/watch?v=LxYgsyKXQVg

40. Reproduction • Sexually dimorphic: visible differences between males and females • Externally, males have claspers which are modified pelvic fins used for sperm delivery • Testes and ovaries are internal • Mating is vicious. Therefore, female skin is twice as thick as males because males will bite the females while mating • Sexes often segregate and only come together to mate • Females can store sperm for a year until the eggs are ready for fertilization

41. Reproduction • Sharks have young in three different ways. After internal fertilization, some species lay a thick egg case that encloses the shark embryo (seen in the photo here). Most species are ovoviviparous, which means that the shark hatches and develops within the female shark and is born live. A third way (viviparous) is similar to human development, where the young shark grows within the female and gets nutrients from a placental link to the mother

42. embryo

43. 70% of the sharks living today have developed a method to care for their brood inside the female’s body (viviparity or ovoviviparity) • 30% of all sharks lay eggs (oviparity) • Gestation 6-22 months • New borns called “pups”

44. Shark embryo in egg case

45. Shark Reproduction • “mermaid’s purse” – egg case • Several months-one year to hatch. Hatch faster in warmer water • Example: Lesser-spotted Dogfish

47. A January 2013 study in the journal PLoS ONE shows that embryonic bamboo sharks in egg cases can react to predation signals. The embryos in this study were exposed to electric fields that simulate the shark's predators and, in response, the sharks stop all gill movement and hold still so as not to alert the predator of their existence

48. Intrauterine Cannibalism in Sharks • Adelphophagy- shark embryos eating each other

49. Two forms of within-the-womb cannibalism are known in sharks. The most extreme form of intrauterine cannibalism — in which the largest and strongest embryo actually consumes its lesser womb-mates — is termed "embryophagy" or, more colorfully, "adelphophagy"— literally "eating one's brother". To date, adelphophagy is known only in the Sandtiger.

50. Sandtiger shark