Bellwork: 02/20/2013 – Don’t start water changes yet 1)What is the defining characteristic of Chondrichthyes? 2)What are the two subclasses & give examples of each: 1

Bellwork: 02/20/ Continued 3)What is the name of the body form of sharks? 4)When did the radiation of chondrichthyes begin? What is the earliest period that scientists have found scales of chondrichthyes? 2

Bellwork: 02/20/2013  Change the water on your tank.  Please scrub the glass & check the filters. Class Chondrichthyes 3

Bellwork: 02/22/2013 Collect the following data: Salt Water Tanks Only: - Phosphate   Nitrate- Calcium  Nitrite- Water Hardness  Ammonia  pH  Temperature Make sure to clean out any excess food from your filter and gravel/sand. Scrub off the inside of the glass & clean the outside the inside of the glass & clean the outside with Windex once you are finished.

Class Chondrichthyes 5 Sharks, Skates, Rays and Chimeras

Class Chondrichthyes 6  Subclass Elasmobranchii Sharks Skates and Rays  Subclass Holocephali Chimaeras (Ratfish)  Traits  Habitats

Bellwork: 1)List 3 differences between skates & rays: 2)Which organ is responsible for the buoyancy of many chondrichthyes? 3)List & describe respiration methods in chondrichthyes: Class Chondrichthyes 7

8 Class Chondrichthyes - Rays  Subclass Elasmobranchii 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

Class Chondrichthyes 9 Class Chondrichthyes - Skates  Subclass Elasmobranchii 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)

Class Chondrichthyes 10 Class Chondrichthyes - Chimeras  Subclass Holocephali Possess cartilaginous skeleton, intromittent organs, spiral valve intestine, and oil filled liver 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

Class Chondrichthyes 11 Chondrichthyes Life History  Strategy of Sharks & Rays Produce precocial (well developed at birth) young with high survival rates Slow growing, long lived, and reach sexual maturity at a late age (13 to 19 years)

Class Chondrichthyes 12 Adaptations  Buoyancy  Respiration  External covering  Feeding  Movement  Sensory systems

Class Chondrichthyes 13 Buoyancy  Huge oil-filled liver A shark that has an air weight of 1,000 kg. weighs only 3.3kg in water  Lift created by a heterocercal tail

Class Chondrichthyes 14 Caudal Fin Types  Homocercal – two symmetrical lobes

Class Chondrichthyes 15 Caudal Fin Types  Heterocercal – much larger dorsal lobe

Class Chondrichthyes 16 Respiration  Chondrichthyes employ 3 different methods of respiration “Two pump” method  Ram ventilation Spiracles

Class Chondrichthyes 17

Class Chondrichthyes 18 Respiration  Chondrichthyes employ 3 different methods of respiration “Two pump” method  Ram ventilation – species swims with mouth open Spiracles

Class Chondrichthyes 19 Respiration  Chondrichthyes employ 3 different methods of respiration “Two pump” method  Ram ventilation – species swims with mouth open Spiracles – small holes behind each eye that opens to the mouth in

Class Chondrichthyes 20 Respiration Spiracles – small holes behind each eye that opens to the mouth in. This allows water to be drawn in from above the organism

Spiracle Class Chondrichthyes 21

Class Chondrichthyes 22 External Covering  All Chondrichthyes have placoid scales in one form or another  Placoid scale modifications Spine of stingray, dorsal spine of dogfish, defensive spines in the skate, and teeth

Class Chondrichthyes 23 External Covering Sting Ray Barb:

Class Chondrichthyes 24 External Covering Dogfish Spine

Class Chondrichthyes 25 Feeding  Most are specialized predators and have dentition that reflects their lifestyle Sharks that prey on fish and marine mammals have triangular blade-like teeth oUsed for grabbing and tearing oCan exert biting pressures of 2,800 kg/cm 3 Teeth are constantly being shed and replaced oUp to 30,000 in a lifetime

Class Chondrichthyes 27 Feeding  Digestion Spiral valve

Class Chondrichthyes 28 Circulatory  Pelagic sharks have rete mirabile (“wonderful net”)  Blood flows both ways in capillaries.  Arteries & veins are very close to each other

Class Chondrichthyes 29 Circulatory  This lowers blood pH allowing oxygen to unbind from hemoglobin & increase the overall oxygen saturation in the blood.  Allows thermoregulation, faster ATP breakdown, and ultimately faster swimming

Class Chondrichthyes 30 Sensory Systems  Sharks have well-developed sensory system which acts in concert to locate prey and find their way around the environment Some species can detect a drop of blood as dilute as 1 part per billion Also, very good at following an odor trail

Class Chondrichthyes 31 Sensory Systems  Hearing  Olfaction  Lateral line

Class Chondrichthyes 32 Sensory Systems  Visual systems are well developed for use during night and day Tapetum lucidum = increased vision at night  Nictitating membrane

Class Chondrichthyes 33 Sensory Systems  Visual systems are well developed for use during night and day Tapetum lucidum = increased vision at night  Nictitating membrane

Class Chondrichthyes 34 Sensory Systems  Nictitating membrane – transparent 3 rd eyelid

Sensory Systems

Class Chondrichthyes 41 Sensory Systems  Ampullae of Lorenzini – electroreceptors (sense biological electric fields)  Tonic Immobility Tonic Immobility  Tonic Immobility #2 Tonic Immobility #2

Class Chondrichthyes 43 Chondrichthyes Reproduction  Most species have extended gestation periods in egg cases or in the body cavities of females Young traits Internal fertilization, through the use of claspers on the male

Class Chondrichthyes 44 Chondrichthyes Reproduction  Oviparity – lays eggs (little or no embryonic development within the mother)  Viviparity – internal development Yolk-sac Viviparity Uterine Viviparity Cannibal Viviparity Placental Viviparity

Class Chondrichthyes 45 Oviparity - Egg Laying  Oviparity

Class Chondrichthyes 46 Oviparity - Egg Laying  Oviparity Oviparity

Class Chondrichthyes 47 Viviparity  Yolk-sac Viviparity (Ovoviviparity) Eggs are produced and retained inside the mother Shell disappears and young are retained until fully developed  Uterine Viviparity Mother secretes nutrient rich fluid which is taken up through the skin of the embryo

Class Chondrichthyes 48 Cannibal Viviparity  Young in each oviduct consume unfertilized eggs or other siblings

Class Chondrichthyes 49 Placental Viviparity  Nutrients are supplied to the embryo directly from the mother via a umbilical cord

In groups of two/three:  Angel SharkRiver Stingray  Wobbegong Shark  Blacktip Reef SharkAmerican Round  Bull SharkStingray  Goblin SharkElectric Ray  Great White SharkBottlenose Skate  Hammerhead SharkManta Ray  Mako SharkWhip-tail sting Ray  Nurse Shark Ghost Shark/elephant shark  Whale SharkRatfish (not rattail)  Tiger SharkGiant Stingray 51