chondrichthyes & agnatha

Chondrichthyes & Agnatha

Sienna Navarro 9B

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(3-4m) / Migrate to sea (12-20m) Develop teeth on sucking disks

Spawning Phase (3m) / 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 System

• Scavenger• Eats dead animals

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 System Cutaneous 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/

Characters/skeleton.html• http://petrifiedwoodmuseum.org/SOChondrichthyans.htm• http://www.ucmp.berkeley.edu/vertebrates/basalfish/chondrofr.html• http://www.newworldencyclopedia.org/entry/Agnatha#Fossil_agnat

hans• http://biostor.org/cache/pdf/d3/c7/a7/d3c7a7457e177dd918a47080

52141bb4.pdf• http://www.waterencyclopedia.com/En-Ge/Fishes-Cartilaginous.htm

l#b• http://www.scribd.com/doc/38167359/Bio-Presentation-Chondrichth

yes• http://en.wikipedia.org/wiki/Elasmobranchii• http://www.bio.davidson.edu/courses/anphys/2000/martin/introduct

ion.html• http://www.google.com/search?um=1&hl=en&q=organic%20detrit

us&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&biw=1088&bih=570&ie=UTF-8&sa=N&tab=iw&ei=2xFET4G7BcGg0QW_t7mPDw

• http://en.wikipedia.org/wiki/Hagfish• http://staff.tuhsd.k12.az.us/gfoster/standard/zoagnath.htm

Bibliography• http://www.aquaticcommunity.com/mix/hagfish.php• http://www.livescience.com/13025-hagfish-eating-skin-gills-scaven

ger.html• http://en.wikipedia.org/wiki/Peritrophic_matrix• http://answers.yahoo.com/question/index?qid=20100307190830A

AE85Al• http://www.sciencedaily.com/releases/2011/02/110202132340.htm• http://www.enchantedlearning.com/subjects/sharks/anatomy/Diges

tion.shtml• http://answers.yahoo.com/question/index?qid=20080212214748A

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