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Chondrichthyes & Agnatha

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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. - PowerPoint PPT Presentation

Text of Chondrichthyes & Agnatha

Chondrichthyes & Agnatha

Chondrichthyes & AgnathaSienna Navarro 9BChondrichthyesMeaningIt comes from the Greek words chondr and ichthyes = cartilaginous fish cartilage fish

ChondrichthyesFirst FossilComes from the early Devonian age416 million years agoElasmobranches: Cladoselache

ChondrichthyesNumber of Species934 species:383 species of sharks516 species of rays35 species of chimaeras

ChondrichthyesCharacteristicsEndoskeleton entirely cartilaginousTough skin covered in dermal denticles No Swim BladderTwo chambered heartAcute sensesSharks shed and replace teeth

ChondrichthyesLife Cycle & ExpectancyAverage life expectancy: 20-50 years

Longest living species: whale shark 100-150 years

3 types of embryonic development:Oviparous: egg birthOvoviviparous: live egg birthViviparous: live birthChondrichthyesOviparous- egg birthFemale shark deposits eggs cases in seaDeveloping embryo receives nutrients from a yolk formed prior to fertilization

ChondrichthyesOvoviparous- live egg birthFemale retains membrane covered eggs

Embryo sheds membrane develops in uterusSome species receive nutrients from direct lining Other species the embryo obtains nutrients by swallowing eggs / other embryosChondrichthyesViviparous- live birthEmbryo and attached yolk grow in uterusOutside layer of yolk contacts mothers uterus Receives nutrients

ChondrichthyesDigestive SystemSwallow food whole or in large pieces

Strong acids and enzymes used to dissolve foodCreates liquid mushNutrients absorbed in intestine

Indigestible things are vomitedChondrichthyesRespiratory SystemSpecies 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 gillsChondrichthyesCirculatory SystemClosed circulatory systemTwo chambered heart:Atrium VentricleAtrium pumps blood to ventricleVenticle pumps blood to conusBlood travels from conus to gillsOxygenated blood flows throughbodyBlood returns to atrium

ChondrichthyesSensory SystemOne inner earDetects sound, acceleration, gravity

Lateral line

Eye sightSensitive to light and moving objects

SmellVery acuteNot connected with the mouth Barbels: responsive to chemical movement

AgnathaAgnathaMeaning:It translates to no jaws

Number of Species84 speciesLampreys Hagfish

First FossilAppeared during Cambrian period: 524 million years agoMyllokunmingia

AgnathaCharacteristicsJaws are absentNo appendages7+ gill pouches The digestive system lacks a stomachCartilaginous skeletonTwo chambered heartsSlender, eel-shaped bodyNotochord persists in adultsProvides support

AgnathaLamprey: Life Cycle & ExpectancyEggs hatch - become larvae

Larvae live in river mud from 3-10+ yearsFeed off of decaying organisms and fecal matter

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

Spawning Phase (3m) / DeathLay eggsDie within the month spawning

AgnathaLamprey: Digestive SystemAttack preyAttach mouth to preys bodyCut through the skin and scalesFood = fish bloodMouth Pharynx EsophagusEsophagus directly to intestine (nutrients absorbed)Waste released through anus

Dual immune defense system

AgnathaHagfish: Life Cycle & ExpectancyLittle is knows of hagfish life span Born fully developedHermaphroditicChoose sex during mating season (can alternate)Females lay small number of eggs for their sizeLive in numbers as large as 15,000

AgnathaHagfish: Diet & Digestive SystemScavengerEats dead animalsDevours from inside outAbsorb nutrients through their skin and gillsMouth is designed to tear flesh

Slow metabolism Can survive months between feedingsFood is enclosed in permeable membraneWaste is excreted

AgnathaRespiratory SystemCutaneous Respiration

DiffusionDissolved oxygen diffuses into bloodCarbon dioxide diffuses out

AgnathaSensory System10 cranial nervesNo external earsNo eyelids

Hagfish:Poor visionReleases slimy mucus when in dangerLateral line system (sense water currents/vibrations)Lamprey:Lateral line system Medial nostril (smell perceiving chemicals in water)Pineal organ (perceives light/dark)