Chondrichthyes Agnatha Sienna Navarro 9 B Chondrichthyes Meaning

Chondrichthyes & Agnatha Sienna Navarro 9 B

Chondrichthyes �Meaning • It comes from the Greek words chondr and ichthyes = cartilaginous fish cartilage fish

Chondrichthyes �First Fossil • Comes from the early Devonian age • 416 million years ago �Elasmobranches: Cladoselache

Chondrichthyes �Number of Species • 934 species: � 383 species of sharks � 516 species of rays • 35 species of chimaeras

Chondrichthyes �Characteristics • • • Endoskeleton entirely cartilaginous Tough skin covered in dermal denticles No Swim Bladder Two chambered heart Acute senses Sharks shed and replace teeth

Chondrichthyes �Life Cycle & Expectancy • Average life expectancy: 20 -50 years • Longest living species: whale shark 100 -150 years • 3 types of embryonic development: �Oviparous: “egg birth” �Ovoviviparous: “live egg birth” �Viviparous: “live birth”

Chondrichthyes �Oviparous- “egg birth” • Female shark deposits eggs cases in sea • Developing embryo receives nutrients from a yolk formed prior to fertilization

Chondrichthyes �Ovoviparous- “live egg birth” • Female retains membrane covered eggs • Embryo sheds membrane develops in uterus �Some species receive nutrients from direct lining �Other species the embryo obtains nutrients by swallowing eggs / other embryos

Chondrichthyes � Viviparous- “live birth” • Embryo and attached yolk grow in uterus • Outside layer of yolk contacts mother’s uterus • Receives nutrients

Chondrichthyes �Digestive System • Swallow food whole or in large pieces • Strong acids and enzymes used to dissolve food �Creates liquid mush �Nutrients absorbed in intestine • Indigestible things are vomited

Chondrichthyes �Respiratory System • Species breathe through 5 -7 gills • Pelagic fish must continue swimming to keep oxygenated water moving though their gills • Demersal fish pump water in through spiracles; out through gills

Chondrichthyes �Circulatory System • Closed circulatory system • Two chambered heart: �Atrium �Ventricle • Atrium pumps blood to ventricle • Venticle pumps blood to conus • Blood travels from conus to gills • Oxygenated blood flows through body • Blood returns to atrium

Chondrichthyes � Sensory System • One inner ear �Detects sound, acceleration, gravity • Lateral line • Eye sight �Sensitive to light and moving objects • Smell �Very acute �Not connected with the mouth �Barbels: responsive to chemical movement

Agnatha

Agnatha � Meaning: �It translates to “no jaws” � Number of Species • 84 species • Lampreys • Hagfish � First Fossil • Appeared during Cambrian period: • 524 million years ago • Myllokunmingia

Agnatha �Characteristics • • Jaws are absent No appendages 7+ “gill” pouches The digestive system lacks a stomach Cartilaginous skeleton Two chambered hearts Slender, eel-shaped body Notochord persists in adults �Provides support

Agnatha �Lamprey: Life Cycle & Expectancy �Eggs hatch - become larvae �Larvae live in river mud from 3 -10+ years �Feed off of decaying organisms and fecal matter �Metamorphic Phase(3 -4 m) / Migrate to sea (12 -20 m) �Develop teeth on sucking disks �Spawning Phase (3 m) / Death �Lay eggs �Die within the month spawning

Agnatha �Lamprey: Digestive System • Attack prey • Attach mouth to prey’s body • Cut through the skin and scales • Food = fish blood • Mouth Pharynx Esophagus • Esophagus directly to intestine (nutrients absorbed) • Waste released through anus • Dual immune defense system

Agnatha �Hagfish: Life Cycle & Expectancy � Little is knows of hagfish life span • Born fully developed • Hermaphroditic • Choose sex during mating season (can alternate) • Females lay small number of eggs for their size • Live in numbers as large as 15, 000

Agnatha �Hagfish: Diet & Digestive • Scavenger • Eats dead animals System �Devours from inside out �Absorb nutrients through their skin and gills �Mouth is designed to tear flesh • • Slow metabolism Can survive months between feedings Food is enclosed in permeable membrane Waste is excreted

Agnatha �Respiratory � Cutaneous System Respiration � Diffusion • Dissolved oxygen diffuses into blood • Carbon dioxide diffuses out

Agnatha �Sensory System • 10 cranial nerves • No external ears • No eyelids • Hagfish: �Poor vision �Releases slimy mucus when in danger �Lateral line system (sense water currents/vibrations) • Lamprey: �Lateral line system �Medial nostril (“smell” perceiving chemicals in water) �Pineal organ (perceives light/dark)

Bibliography • • • http: //palaeo. gly. bris. ac. uk/palaeofiles/fossilgroups/chondrichthyes/Characte rs/skeleton. html http: //petrifiedwoodmuseum. org/SOChondrichthyans. htm http: //www. ucmp. berkeley. edu/vertebrates/basalfish/chondrofr. html http: //www. newworldencyclopedia. org/entry/Agnatha#Fossil_agnathans http: //biostor. org/cache/pdf/d 3/c 7/a 7/d 3 c 7 a 7457 e 177 dd 918 a 4708052141 bb 4. pdf http: //www. waterencyclopedia. com/En-Ge/Fishes-Cartilaginous. html#b http: //www. scribd. com/doc/38167359/Bio-Presentation-Chondrichthyes http: //en. wikipedia. org/wiki/Elasmobranchii http: //www. bio. davidson. edu/courses/anphys/2000/martin/introduction. html http: //www. google. com/search? um=1&hl=en&q=organic%20 detritus&bav=o n. 2, or. r_gc. r_pw. r_qf. , cf. osb&biw=1088&bih=570&ie=UTF 8&sa=N&tab=iw&ei=2 x. FET 4 G 7 Bc. Gg 0 QW_t 7 m. PDw http: //en. wikipedia. org/wiki/Hagfish http: //staff. tuhsd. k 12. az. us/gfoster/standard/zoagnath. htm

Bibliography • • http: //www. aquaticcommunity. com/mix/hagfish. php http: //www. livescience. com/13025 -hagfish-eating-skin-gills-scavenger. html http: //en. wikipedia. org/wiki/Peritrophic_matrix http: //answers. yahoo. com/question/index? qid=20100307190830 AAE 85 Al http: //www. sciencedaily. com/releases/2011/02/110202132340. htm http: //www. enchantedlearning. com/subjects/sharks/anatomy/Digestion. shtml http: //answers. yahoo. com/question/index? qid=20080212214748 AAl. EU 7 r