MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.1

FocusQuestionWhat are cartilaginous fish?What features differentiate them andwhere are their habitats?Howdohumansaffectthemandwhyaretheyimportant?

ObjectivesStudents will research the cartilaginous fish class and their defining characteristics. Studentswilllearnto:

• Identifythedefiningfeaturesofthecartilaginousfish.• Explainwhatresourcestheydependonandwheretheycanbefound.• Demonstrateknowledgebyresearchingandpresentingaspeciesofcartilaginousfish.

Studentwilldiscusshowtheseorganismscanbeprotectedforfuturegenerations.Thiswillbeaproject-basedactivitywherestudentswilldissectadogfish.

BackgroundThecartilaginousfishclass,orChondrichthyes,isdefinedbyoneparticularfeature:a

skeletonmade of cartilage, a dense, rubberymaterial that is lighter andmore flexible thanbone.Thisclassencompassesallsharks,raysandskates,aswellassawfishandchimaeras.Allmodern Chondrichthyes are thought to have evolved from acanthodians almost 400 millionyears ago, fromwhich they retained a few common characteristics, including their skeleton.Becauseofthiscartilage,thespeciesinthisclassdonothavebonemarrow,sotheirredbloodcells,essentialfordeliveringoxygenthroughoutthebody,areproducedinthespleen.

Asidefrombeingjawedvertebrates,allChondrichthyesalsosharepairednostrils,gills,scales, and a multi-chambered heart. Unlike fish, these species have no swim bladder. Therespiratory systemoftheseorganisms reliesuponfivetosevengillpairsontheundersideorside of the head, which extract oxygen as water passes through them. Some species mustremainmoving inorder tokeepwater flowing through their gills,whileothershaveadaptedactive-pumpingspiracles.Thespiracleallowsspecieslikethenursesharktorest,whilethreshersharksandmackerelsharksnolongerhavethemandmustmaintainmotion.

The scalesof these speciesare calleddermaldenticles andarephysically similar torowsoftinyteeth,givingtheirskinthedistinct sandpaper-liketexturethatbothprotectsandstreamlines.Thescalesofbonyfishgrowinsize,whilethoseoftheChondrichthyesclassformnewscalesinnewspacesasthebodygrows.Otherfeaturesofthesespecies,suchasthenoseofsawfishesandthespinesofstingrays,arealsostructurallymodifiedscales.Ratherthanbeingfirmlyattachedtotheirjaws,theteethofChondrichthyesareimbeddedinafibrousmaterialsothatwhenonebecomesbrokenorworndown,itisreplacedbyanothermovingforwardfrombehind,withnewtoothbudsdevelopingasneeded.

While some species of this class lay egg cases, most are consideredovoviviparous,withfemalesgivingbirthtoliveyoung.Malesofthesespeciestendtohavemodifiedfinscalledclaspersthatareusedtoinseminatethefemale.Pregnantfemalesoftenstopeatingandselectisolatednurseryareastogivebirth,butoftenleaveshortlythereafter.

MarineConservationScience&Policy:CartilaginousFishandDogfish

DissectionGradeLevel:

4th-12th

SubjectAreaScienceBiologyDuration1.5Hrs

BodyofKnowledgeLifeScienceNatureofSciencePhysicalScience

BigIdeaOrganizationandDevelopmentofLivingOrganisms.ThePracticeofScience

StandardsSC.3.L.15.1Classifyanimalsintomajorgroupsaccordingtotheirphysicalcharacteristicsandbehaviors.SC.5.L.17.1Compareandcontrastadaptationsdisplayedbyanimalsthatenablethemtosurviveindifferentenvironmentssuchasbehaviorsandphysicalcharacteristics.

SC912.L.14.2Relatestructuretofunctionforthebodypartsofanimals.

Benchmarks:

MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.2

BackgroundMost speciesalso featurea tapetum lucidum, a layerof tissue thatmaximizes light

reflection in the eye, allowing for superior night vision. While this adaptation is particularlyuseful to thenocturnal carnivoresof theChondrichthyes class, feedingduring theday is alsocommon.Thedietofthisclassvaries,someeatingalmostanythingfrombirdstosealstotunatoothersharks;otherslikethewhale,baskingandmegamouthsharkspreferplankton.

Whilea fewof these species venture intobrackishand freshwater,mostare foundstrictly inmarine habitats.While some species like the bonnethead shark spend their entireliveswithinahundredmilerange,othersliketheblueandmakosharksmigratethousandsofmilestobreedandhunt.Themajesticgoldencow-noserays,measuringupto6½feet,migratetwiceayearfromMexicotoFloridatoNewEnglandingroups,orfevers,ofupto10,000!

Thereareat least1,100knownspeciesof cartilaginousfish,ranging insizefromtheshort-nosedelectricrayat4 inchestothemassivewhaleshark,whichgrowsupto30ft.andcanweighup to10 tons.Colorationvaries,butmost featureadistinct lateral lineandmanyshowcountershading, adark-upperand light-lowerbody thathelps them camouflage in thewater.Whilemostsharkslivebetween20and30years,andmostraysandskatesanaverage40-50years,thespinydogfishandwhalesharkhavebeenknowntosurviveforoveracentury.Mostcartilaginousfishareconsideredapexpredators,organismsatthetopoffoodchains.Asapex predators, these organisms play a crucial role in sustaining the health of the marineecosystem,maintaining stability by keeping the prey species’ populations balanced.Withoutsharks, the increased populations of smaller fish cause a crash in plankton, upon which theentire foodwebdependsasprimaryproducers.Humans alsouse cartilaginous fish to createvariousproducts,includingmeat,sharkliveroil,leather,jewelry,rope,andevendrumheads.

Despite their importance, cartilaginous fishhavedeclined by80%,withone thirdofspeciesfacingextinction.Thesepopulationdropsaremostlyduetoanthropogenic,orhuman-causedthreats.Marinepollutionfromfisheries,plasticthatamassesinapexpredatorsthroughbioaccumulation, agricultural and urban runoff, coastal development and sewage destroyhabitat and prey populations. Overfishing threatens these species on multiple levels: bydecreasingtheirfoodsourcesaswellasunintentionallytanglingtheminnetswheretheyoftendieneedlesslyasbycatch.Byfarthegreatestthreattomostspeciesisfishing,as126,000tonsof rays and an estimated 100million sharks are killed each year, about 73million of thesedeaths due to finning. Finning refers to the practice in which a fisherman cuts off just theshark’sfin,throwingthebodyoverboardtodieaslowdeathbysuffocationorpredation.Theproblems inthefoodwebarealreadyevident inan increase in jellyfishnumbersandasteepdecline in fish populations. In order to protect these fascinating creatures, individuals canreduceplasticuse,symbolicallyadoptagreatwhite,donatetoconservationorganizations,urgegovernment officials to limit fisheries and increase marine protected areas, consume onlysustainableseafood,andeducateothersontheimportanceofallcartilaginousfish.

SupplementalResources1-“Sharks.”NationalGeographicEducation.hfp://educa,on.na,onalgeographic.org/search/?q=sharks2-“SharksandRays.”SmithsonianNaturalMuseumofNaturalHistory—OceanPortal.hfp://ocean.si.edu/ocean-life-ecosystems/sharks-rays3-VirtualTour:“Sharks:PredatorsinPeril.”OdysseyEarth.hfp://www.odysseyearth.com/videos/sharks-predators-in-peril/

Vocabulary:

CartilaginousFish:Aclassoffishcharacterizedbyarubberycartilageskeleton,complexanddiversebodies,andspeciesthatincludesharks,rays,skates,sawfishandchimaeras.Cartilage:Adenseconnectivetissuethatislighterandmoreflexiblethanbone.DermalDenticles:Thetooth-likescalesofcartilaginousfish.Ovoviviparous:Producingyoungbymeansofeggsthathatchwithinthefemalebody.

Claspers:Apairofappendagesonmalesharksandrays,usedforreproduction.

TapetumLucidum:Alayeroftissuewithintheeyethatmaximizeslightreflectiontoallowforsuperiornightvision.Gills:Pairedrespiratoryorgansofwhichextractoxygenfromwaterflowingoverthesurface.

Countershading:Aprotectivecolorationofsomefishwithdistinctdelineationbetweenadarkupperandalightlowersection.ApexPredators:Anorganismresidingatthetopofafoodchain,uponwhichnootherorganismsprey.

Bycatch:Theunwantedfishandmarineorganismscaughtincommercialfishingnets.Finning:Aprocessbywhichonlythefinisremovedfromasharkwhilethebodyislefttodie.

MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.3

DogfishDissectionMaterials

• Alargedissectiontray• Surgicalscissors• Scalpel• Probe• Forceps

Procedure

1. Dividestudentsintosmallgroupsof3-4.Explainthatasteamsofichthyologists,eachgroupwillbedissec,ngadogfishspecimeninordertobeferunderstanditsorgansandtheirfunc,ons.HandeachgrouptheirmaterialsandreadtheGuidelinestogether.Anincisiondiagramshouldbeplacedontheboardordemonstratedonanoverheadprojector.

2. Studentsmaywishtoassignonepersontonotetakingduringthedissec,on,comple,ngtheassignedsec,onsoftheworksheet.

3. Studentsshouldmeasureandexaminetheexternalfeaturesofthedogfish.4. Studentsshouldbeginthedissec,onbycarefullyfollowingtheincisiondiagram.5. Studentsshouldexaminethemusculatureofthespecimen.6. Havestudentsexaminethediges,vesystemofthespecimen.Theyshouldthen

removethoseorganstoexaminetheurogenital,nervousandcirculatorysystems.7. Studentsshouldcleanupamerthedissec,onbyplacingalldogfishpartsinthebag,

securethebagwitharubberband,andplacethebaginoneoftheusedspecimenboxes.Theyshouldwashalldissec,ontoolsandthetray,andreturntoolsandtraytotheteacher.

8. StudentsshouldallcompletetheirSharkAnatomyworksheets.Goovertheques,onsasaclassandencouragediscussionontheimportanceothescien,ficmethod,thesimilari,esanddifferencestohumananatomy,andtheevolu,on,func,onandimportanceofthebody’ssystems.

9. Dissec,onExtension:Studentsshouldresearchanddiscusstheethicsofdissectionwithaparentoradult.Studentsshouldprepareaoflistprosandconsandformulatetheirownopinion.Studentsshouldsummarizebothargumentsandelaboratetheirowndecisioninaparagraph.

AnswerKey1.D 5.E2.C 6.B3.F 7.A4.G8.Cartilaginousfishplayanimportantroleinmostmarinefoodwebsasapexpredators,helpingtomaintainbalanceinecosystems.9.Cartilaginousfisharethreatenedbyfinningandunsustainablefishingpracticesthatreducepreyspeciesandleadtobycatchofcartilaginousfish,andotheranthropogenicfactorslikebioaccumulationfromcontaminants.10.Individualscanhelpprotectthesespeciesbyeatingsustainablycaughtseafood,supportingwildlifeorganizationsandprogramslikeAdopt-a-Shark,andeducatingothers.

CartilaginousFish:Aclassoffishcharacterizedbyarubberycartilageskeleton,complexanddiversebodies,andspeciesthatincludesharks,rays,skates,sawfishandchimaeras.ApexPredators:Anorganismresidingatthetopofafoodchain,uponwhichnootherorganismsprey.Bycatch:Theunwantedfishandmarineorganismscaughtincommercialfishingnets.

Finning:Aprocessbywhichonlythefinisremovedfromasharkwhilethebodyislefttodie.

Havestudentsresearchanothercartilaginousspecieswithaparentoradult.Havethemcutconstructionpaperlengthwiseintobookmarksize.Ononeside,thestudentshouldillustratetheirchosenspecies,whiletheothersideshouldfeatureitsname,habitat,food,andthreefunfacts.

HavestudentscompletetheCartilaginousFishworksheetinclass.Intheirsciencejournal,havethemwriteaparagraphsummarizingtoday’slessonanditsrelevancetothem.

UniversityofMiami–SharkResearch&ConservationProgram

ExtensionActivity:

Assessment:

Vocabulary:

ProgramPartner:

MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.4

MSCP

SharkAnatomy

SectionII:TheDigestiveSystem5.Illustratethedigestivetractfrommouthtoanus.Labeltheorgans.

6.Howdoestheoilintheliveraidinbuoyancy?________________________

_________________________________

7.Howdoestheshark’sdigestivesystemcomparewiththatofahuman?_______

_________________________________

_________________________________

Sec,onI:ExternalAnatomy1.Illustratetheexternalanatomy.Measurethespecimenandlabelfeatures.

2.Whatinterestingthingsdoyouobserveabouttheskinandexternalorgans?_____________________________________________________________________

3.Whatpurposemightthelaterallinesystemserve,especiallyforafishinmurkywaters?______________________________________________________________

4.Istheshark’sskinasthickasyouexpectedittobe?Whyorwhynot?__________

_____________________________________________________________________

9.Unlikeamammal’sheart,theshark’sheartcirculatesdeoxygenatedblood.Whereisthebloodoxygenatedintheshark?_____

____________________________________

10.Isthesharkmaleorfemale?Whatinternalandexternalfeatureshelpedyouidentifysex?__________________________

____________________________________

8.Illustratetheheart.

Sec,onIII:InternalOrgans

11.Whatisthelargestpartoftheshark’sbrainandwhy?_________________

________________________________________________________________

12.Howistheshark’sskeletondifferentfromourown?__________________

________________________________________________________________

13.Whatdidyoufindinterestingaboutthisdissectionandwhy?___________

________________________________________________________________

SpinyDogfishDissec,on

MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.5

MSCP

CartilaginousFish

8.Whyarecartilaginousfishimportant?____________________________________________________

9.Whataresomeofthethreatsthatareaffectingcartilaginousfish?_____________________________

___________________________________________________________________________________

10.Whatcanyoudotohelpprotectthesefascinatingandimportantcreatures?____________________

___________________________________________________________________________________

Thecartilaginousfishclasscontainsover1,100knownspeciesofsharks,rays,skates,sawfishandmysteriouschimaeras.Thesespeciesvaryinsize,shape,colorandbehavior,butallfeatureaskeletonmadeofcartilage,gills,nostrils,andtiny,tooth-likescalesthatprotecttheirskinandfeellikesandpaper.Cartilaginousfishplayanessentialroleintheecosystem,butmanyareendangered.

Iden,fythespeciesintheabovephotos:

1. ______Thelarge-toothedsawfishcanuseitslongsnouttodigthroughsedimentorcutpreyinhalf.2. ______Themajes,cmantaraycanhaveawingspanof15m.andliveuptoahundredyears.3. ______ThelifleskatelivesintheAtlan,candisomenusedformedicalresearch.4. ______Despitebeingtheworld’slargestfish,thewhaleshark’sdietconsistsoftheocean’ssmallestorganisms,

filteringplanktonthroughitsmouth.5. ______ThespofedchimaerahuntssmallfishandcrustaceansoffthePacificcoastofNorthAmerica.6. ______Becauseitseyesareonbothsidesofitsunusualhead,thehammerheadisabletoscanmoreoftheoceanfor

itsfavoritefood:s,ngrays.7. ______Thegoldencow-noseraymigratesannuallyfromMexicotoFloridaingroupsofover10,000.

A B C

D E F

G