Bellwork: 02/12/2014 – Don’t start water changes yet What is the defining characteristic of Chondrichthyes? What are the two subclasses & give examples of each:

Bellwork: 02/20/2013 - Continued What is the name of the body form of sharks? When did the radiation of chondrichthyes begin? What is the earliest period that scientists have found scales of chondrichthyes?

Bellwork: 02/12/2014 Change the water on your tank. Please scrub the glass & check the filters. Clean of the glass lids as well Class Chondrichthyes

Sharks, Skates, Rays and Chimeras Class Chondrichthyes Class Chondrichthyes

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

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

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 Class Chondrichthyes

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 Class Chondrichthyes

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 Class Chondrichthyes

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 Class Chondrichthyes

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

Buoyancy Huge oil-filled liver Lift created by a heterocercal tail 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 Class Chondrichthyes

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

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

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

Class Chondrichthyes

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

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 Class Chondrichthyes

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

Spiracle Class Chondrichthyes

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 Class Chondrichthyes

External Covering Sting Ray Barb: Class Chondrichthyes

External Covering Dogfish Spine Class Chondrichthyes

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 Used for grabbing and tearing Can exert biting pressures of 2,800 kg/cm3 Teeth are constantly being shed and replaced Up to 30,000 in a lifetime Class Chondrichthyes Class Chondrichthyes

Class Chondrichthyes

Feeding Digestion Spiral valve Class Chondrichthyes

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

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 Class Chondrichthyes

Circulatory . Class Chondrichthyes Class Chondrichthyes

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 Class Chondrichthyes

Sensory Systems Hearing Olfaction Lateral line Class Chondrichthyes

Sensory Systems Class Chondrichthyes Class Chondrichthyes

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

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

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

Sensory Systems Class Chondrichthyes

Sensory Systems Class Chondrichthyes

Sensory Systems Class Chondrichthyes

Sensory Systems Class Chondrichthyes

Sensory Systems Class Chondrichthyes

Sensory Systems Class Chondrichthyes

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

Ampullae of Lorenzini Class Chondrichthyes Class Chondrichthyes

Class Chondrichthyes

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 Class Chondrichthyes

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 Class Chondrichthyes

Oviparity - Egg Laying Oviparity Class Chondrichthyes

Oviparity - Egg Laying Oviparity Class Chondrichthyes

Viviparity Yolk-sac Viviparity (Ovoviviparity) Uterine Viviparity 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 Class Chondrichthyes

Viviparity Yolk-sac Viviparity (Ovoviviparity) Class Chondrichthyes

Cannibal Viviparity/oophagy Young in each oviduct consume unfertilized eggs or other siblings (Sand Tiger Sharks) Class Chondrichthyes Class Chondrichthyes

Cannibal Viviparity/oophagy Class Chondrichthyes Class Chondrichthyes

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

Class Chondrichthyes

In groups of two/three: Angel Shark River Stingray Wobbegong Shark Blacktip Reef Shark American Round Bull Shark Stingray Goblin Shark Electric Ray Great White Shark Bottlenose Skate Hammerhead Shark Manta Ray Mako Shark Whip-tail sting Ray Nurse Shark Ghost Shark/elephant shark Whale Shark Ratfish (not rattail) Tiger Shark Giant Stingray