Unit 7 Exam Review

Chondrichthyes – “cartilage fish,” Well developed jaws Cartilaginous skeleton Highly developed sense organs Fusiform body Most have placoid scales Oil-filled liver for buoyancy Elasmobranchii – sharks, rays, and skates (extant and extinct) Holocephali – chimeras such as ghostfish and ratfish

4. Cladoselache: 5. Hybodus: “Branched-toothed” shark Ligamentous band in a whorl-shaped arrangement Homocercal caudal fin No rostrum 5. Hybodus: Heterocercal caudal fin Rostrum Heterodont dentition (more than one type of tooth)

6. Neoselachii: 7. Galeomorpha: 8. Squalomorpha: This is a subset of Elasmobranchii that includes only extant (still living) sharks 7. Galeomorpha: “Normal” sharks, extant Galoids 8. Squalomorpha: The outlying forms of sharks, extant Small brained Live in cold waters (Arctic & Antarctic) Live in deep waters (aphotic)

9. Batoidea: Extant rays and skates

Rays: Thin, flexible, and barbed tails Can be extremely large (25 feet across, weighing several tons) Serrated spines that are very difficult to remove from victim Spines are covered with a thin skin that contains painful toxins once ruptured Predominantly live-bearers (viviparity)

Skates: Fleshy, heavy tails Relatively small (1 to 5 feet) Elongated nose Often found in North America Large thorns for defense, but not poisonous Lay eggs (mermaid’s purse [oviparity])

Chimeras: Intermittent organs Single gill slit, no scales Only have 6 permanent teeth for grinding As a group found mostly between 80-2,600 meters, feeding on hard shelled invertebrates

Chondrichthyes Buoyancy: Heterocercal tail Cartilaginous skeleton Large, oil-filled liver instead of a swim/gas bladder

Heterocercal/Homocercal caudal fins:

Three methods of respiration in chondrichthyes: Ram ventilation: species swims with mouth open Two Pump: buccal pumping (diaphragm-like muscles) that allow a chondrichthyes to stay in one place & draw water in & push it out over the gills Spiracles: small holes behind each eye that opens to the mouth in chondrichthyes

Placoid scales & other tissues generated by these cells: Sharp, one-way scales that allow for highly efficient movement through the water The cells that make these scales are also responsible for forming the following: Spine of stingray dorsal spine of dogfish defensive spines in the skate teeth

This allows for light to be amplified in low-light situations Tapetum Lucidum: A layer of reflective tissue that covers the back of the eye This allows for light to be amplified in low-light situations During the daytime/bright life, melanin dilates to cover the tapetum lucidum & reduce the amount of reflected light

Nictitating membrane: A transparent 3rd eyelid This is used to protect the eye when a shark attacks its prey This can also be used to clear debris from the eye

Ampullae of Lorenzini: Electroreceptors from on the most anterior portion of a shark

Lateral line of sharks: Cells that can detect the movement/changes in pressure in the water Sharks can detect changes in water movement up to 100 meters away Oviparity – ovi = egg lays eggs (little or no embryonic development within the mother)

Viviparity – internal development Yolk-sac Viviparity Uterine Viviparity Cannibal Viviparity Placental Viviparity Yolk-sac Viviparity (Ovoviviparity) Eggs are produced and retained inside the mother Shell disappears and young are retained until fully developed Mother secretes nutrient rich fluid which is taken up through the skin of the embryo

Cannibalistic viviparity: Young in each oviduct consume unfertilized eggs or other siblings Placental viviparity: Nutrients are supplied to the embryo directly from the mother via a umbilical cord

Time periods connected with chondrichthyes development & prevalence

Fusiform: Rostrum: Squaloid Sharks: Torpedo-shaped body Nose-like protrusion that hangs over the mouth of a shark This is a highly sensitive area of the shark, covered in electro receptors and chemo receptors Squaloid Sharks: smaller brained mostly live in cold, deep water include the various species of dogfish, the megamouth, and cookie-cutter sharks

Rows of teeth in sharks: Galeoid sharks: the dominant carnivores of shallow waters Live in warm, rich parts of the ocean include hammerheads, tiger sharks, threshers, mackeral sharks, and the whale shark Rows of teeth in sharks: The rows run anterior to posterior, not side-to-side The teeth fold out from the mouth & are constantly replaced Some sharks replace their teeth as often as once every 8 days

Be able to recognize variation in tooth structure & food types:

Flat grinders to eat shelled organisms

Flat grinders to eat shelled organisms

Needle-like teeth for eating relatively small fish & other smaller prey

Reduced teeth & gill rakers for filter-feeding fish such as basking sharks & whale sharks

Reduced teeth & gill rakers for filter-feeding fish such as basking sharks & whale sharks

Broad, serrated teeth to tear & exsanguinate prey:

29. Hyostylic Jaws The jaw is not directly attached to the skull This allows the entire jaw to move forward when attacking prey

30. Spear fishing & its connection to shark attacks on humans: Spear fishermen are the most common victims of shark attacks This method does not kill the hunted fish quickly, allowing a large amount of blood to escape into the water & the electric signal from the thrashing fish to dissipate through the water

31. 4 “most dangerous” types of sharks: Great white Tiger shark Bull shark Mako shark 32. Shark attack deaths relative to other human death rates: Compared to other forms of death, death by shark is exceedingly rare 1 death/year in USA 5 death/year globally

33. Gill nets & bycatch: Prior to the 1980s, this was the most-common cause of shark death (accidental; “bycatch”)

33. Gill nets & bycatch: The number of deaths has not decreased since the 1980s, but instead has been beat out by the intentional catching of sharks on long lines for finning

34. Shark finning & sharkfin soup: Driven by the economic success of Asian markers Tripled since the 1980s Shark fins = $500/kilo Sharkfin Soup = $90/bowl Hong Kong is the largest global importer of shark fins

35. What has caused the rise in shark finning? The rise in economic success of Asian markets The continued poverty in developing nations that leave fishermen with little other choice 36. Example decline in shark populations: Whitetip shark in the Gulf of Mexico Population numbers are down 150 times their numbers in the 1970s

37. Example size (individual) decline in: Whitetip: 33% Mako: 50% Blue: 50% Dusky: 60% Silky: 83%

38. Why are these populations suffering such a rapid decline? Fishing often preferentially removes older animals, Fishing pressure is so intense that animals don’t live long enough to grow to their maximum size. Sharks are long-lived, slow growing, and slow to reach sexual maturity