SharkDissection
08.03.31
Nam e
Partner
Hour
INTRODUCTION:THE SHARK AND MAN
"Who can open the jaws of his face? His teethare terrible round about." Job 41:6
The very mentionof the word sharkhas from ancienttimes instilled within man an almostirrationalfear.
Yet, at the sametime, the cunning, strength,tenacity,and graceof movementof the animal havenever
ceasedto fascinatehim.
Sharkshavein the pastbeenstudiedby ichthyologistsalone.Today, with the popularity of suchfilms as
JawsI and JawsII and the publication of numerouspaperbackson the subject,even the personwithout a
sciencebackgroundis awareof the more dramaticaspectsof sharkbehavior.
The presentday popular interestin sharkscan be tracedto the wartime experiencesof the armedforces.
The sinking of troop transportshipsand the shootingdown of aircraft over the open seasoften endedin
carnageresulting from shark attacks upon those who had survived the guns and torpedoes.
Tell what ichthvolosistsstudv:
SHARKS AND FISH
Biologically, sharksare fish belongingto the phylum Chordataand the subphylum Vertebrata.However,
sharksand their relatives,the rays and skates,are uniqueamongstfrsh in that their skeletonsare made
entirelyof cartilage,not bone.This placesthem in the classChondrichthves,subclassElasmobranchii.
The bony fish, the Osteichthye.t,
possessa gas-filledswim bladderby meansof which they can regulate
their buoyancyallowing the fish to "float" at variousdepthsunderwater. Sharkshave no swim bladders.
They are somewhatheavierthan the water they displace.Thus, once a sharkceasesto move, it sinks.
Coastalspeciesrest on the seafloor in shallow water.However,the sharksof the deeperoceansmust
continuemoving from the moment of birth to the momentof death!If they were to stop swimming,they
would sink and be crushedby the pressureof the deepbelow. Sharksbelong to the OrderSelachii.
Name the shark'stwo closestrelatives:
Name the materialthat makes-upthe skeletonof the shark:
Give the phylum namefor the bony fish:
is not found in sharks:
Name an organ found in bony-fish that
Tell what this organ allows the bony fish to do that the
sharkscannot do:
Give the nameof the scientificprinciple describedabove:
Tell what happensto a shark if it quits swimming:
Regulationof osmoticpressurein marine sharksdiffers from that of their bony relatives.They retain a
high concentrationof urea and other solutesin their body fluids, a concentrationof saltshigher than that in
the surroundingseawater. There is therefore no need for sharksto drink. (Shark "body fluids" are
hypertonic to the oceanwater. Therefore, the hypotonic oceanwater moves INTO their tissuesin an
attemptto dilute the more concentratedbody fluids.)
Fertilization is internal, and most shark "pups" hatch internally, to continue their developmentwithin the
uterus of the mother. After a period of gestation(up to two years in the spiny dogfi sh,Squalusacanthias,
the longestof any vertebrate!)they are born alive as a smallerversionof the adult. This methodof
reproductionis called ovoviviparous. The numberof "pups" in a litter variesfrom two in somespeciesto
sixty in others. Somesharksare oviparous,laying largeeggsenclosedin shells,or egg-cases,
consisting
of hornlike material. They are usually flat and quadrangularshapedwith long tendrils which serveto
anchorthe eggsto seaweedor other objects.
Give the namefor the measurementof the amountof fluid in a cell:
Name two materialsthe sharkretainsthat producesan increasein this value:
Tell how much water a sharkneedsto drink:
Completethe following statement:The shark'sbody fluids are
oceanwater ls
to oceanwater;
to the shark'sbody fluids.
Is fertilization in the sharkinternalor extemal (like most bony fish)?
Give the namefor young developingsharks:
Tell what it meansto be ovoviviparous:
Tell what it meansto be oviparous:
While there are close20,000living speciesof fish, only about300 of theseare sharks.They are divided
into nineteenfamilies,with five families making up 75 per cent of the known species.
Sharksrangein size from a speciesonly six incheslong when matureto the 35-foot basking-sharkand to
the largestof all fish, the whale-shark,reaching50 feet in length and weighing over ten tons. Contraryto
popularbelief, thesetwo largestof sharksare quite inoffensivebeasts,deriving most of their nourishment
from minute planktonicanimals(thosewhich float in the upper layersof the sea).
What percentage(yes,do the calculation)of living fish are sharks?
Calculations:
Name the largestfish ltherefore,the largestshark):
Tell what plankton is:
SPINY DOGFISH SHARK
The spiny dogfish, genusand speciesnamesSqualusacanthias,of the family Squalidae,is our dissection
specimen.The speciesname "acanthias"calls attentionto the animal'smildly poisonousspines,one in
front of eachdorsalfin. It is a relatively small shark,attainingabout 1-meter(3.5 feet) in length and
weighing about 15 pounds.The absenceof an anal fin is characteristicof the entirefamily.
a
Give the taxonomic hierarchy for the shark:
Kingdom:
Phylum:
Subphylum:
Subclass:
Class:
Order:
Family:
Genus:
species:
Common name(3-parts):
Scientihcname:
Tell wherethe speciesname"acanthias" comesfrom:
It is distributedworldwide, from the temperateto the subpolarregions,from the shallowwatersof the seashoreto depthsof 100 fathoms(600 feet).
They are voraciouseaters,feedingon fish, crustaceans,
squid,gastropods,jellyfish, and evenred and
brown algae.The spiny dogfish,as most other sharks,is omnivorous,devouringboth plant and animal
matter.
It is an abundantspecies.On this side of the Atlantic it is infamousfor its disruptiveactivitiesto hshing
operations.It is destructiveof fishing gear;hook and line, netsare bitten and their catchdevouredand
freed.This resultsin a high animal loss to the fishing industry.Except as laboratoryspecimens,no
economicusehasbeenfound for them.
In northem Europeand the British Isles,the spiny dogfish sharkis similarly destructivebut is there
countedas a food fish species.Known as the spurdogor piked dogfish,a greatdeal of it is servedin fish
and chips shops.
Tagging studiesindicatethat the animal hasa life spanof 25-30 years.The male reachessexualmaturity
at the age of 11, the female at 19. Litters are small, generallyfour to sevenpups.The excessivelylong
gestationperiod, two years,longestof any other vertebrate,has alreadybeenmentioned.
In the laboratorythey servetwo functions.First, they serveas dissectionspecimens,illustratingmany
primitive vertebratefeatures,and thus useful in tracing thesefeaturesthrough the higher vertebratesto
man. Second,their relatively small size is a conveniencein housingand caring for live specimensin a
broad rangeof physiologicalresearchsituations,suchas humancardiologyand immunology.
Humans,Homo sapiens,belongsto the classMammalia,whosememberspossessmilk producingglands
in the female (mammary glands) for nursing the young and have skin coveredwith hair or fur.
The dogfish sharkis a comparativelylargedissectionspecimen.Its musclesand intemal organsare clearly
visible. Its nervesand blood vesselsare readily traced.
Tell what it meansto be omnivorous:
Name one economicusefor the dosfish shark:
Give the lifespanof the dogfish shark:
Sometopographicanatomyyou will needto know....On the diagrambelow, label eachof the starred(*'d)
anatomicalfeatures.. ...
Body Planes:
xTransverse (cross):a planethat passesat a right angleto the long axis of a body or body structure,
usually resultingin cranial and caudalportions.
Longitudinal: a planethat extendsfrom cranialto caudalalong the long axis of the body; the longitudinal
plane bisectsthe transverseplane at a right angle.
*Sagittal: a longitudinalplanethat dividesthe body into lateralright and left parts;if this division is into
equalhalves,it is calledmidsagittal.If it is into unequalparts,it is calledparasagittal.
*Frontal (coronal):a longitudinalplanethat extendsfrom cranialto caudaland horizontallyfrom right to
left, dividing the body into ventral and dorsalportions.
Directional Terms:
Rostral: toward the noseend.
+CraniaVanterior: toward the headend.
*CaudaUposterior:towardthe tail end.
*Dorsal: toward the back side.
*Ventral: towardthe belly side.
Superficial: toward the body surface.
Deep: away from the body surface.
Midline: an imaginaryline that bisectsthe body into right and left halves.
Medial: lying closerto the midline relativeto anotherstructure.
Lateral: lying further from the midline relativeto anotherstructure.
Proximal: neara structure'sorigin or point of attachmentto the body.
Distal: away from a structure'sorigin or point of attachmentto the body.
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Extemal Anatomy of the Shark
Fin spine
Anteilor dorsal fin
Lateral tjnc canaf
Oarsallobe ol cauda{fin
Spincte
Posteilar dorsal fin
Extemal'.
nilt slit* \
Pelvic fin
Ventrallobe of caudal fin
Pectaral fin
The sharkis gracefullyelongatedand streamlined.The body shapeis known as fusiform, built for
swimming in the seawith leastpossibleresistance.
The body is divided into three readily identifiableareas:
The head(cranial)- from the pointed snout-likerostrumto the pectoralfins. This includesthe gill region.
The trunk - from the pectoralfins to the pelvic fins.
The tail (caudal)- from the pelvic fins to the end of the caudalfin.
Using brackets(and the descriptionsabove),denotethe threeregionsof the shark'sbody on the diagram
below. Label eachregion. Label the pectoralfrn, pelvic fin, and the caudalfin.
Using your specimenas a guide, draw and label on the diagrambelow the gill slits.
Tell what it meansto have a fusiform bodv:
THE SKIN
Run your hand over the body of the shark from headto tail and feel its smooth texture. Now, run your
hand in the oppositedirection and you will detect a rough, sandpaper-liketexture. As a matter of fact,
shark skin has beenused as an abrasivein the manufactureof furniture for hundredsof years.It was also
usedas a coveringfor sword handlesand tools to preventthem from slipping from one'shand. Sharkskin
was onceknown as "shagreen"and was usedto polish wood.
The entire skin of the sharkis coveredby minute, sharp,tack-like placoid scalesembeddedin the skin
pointing caudally.Thesescalesdiffer considerablyfrom the oval overlappingtransparentscalesof most
bony fish. They are modifications of teeth; thus their nalne, dermal denticles.Their structureand mode of
developmentare similar to the teethof higher vertebrates.Seethe diagramsbelow.
Skin(crosssection)'
Spine
Melanophores
Epidermis
Stratum
germinativum
n)
laxum
) lStratum
Dermis
i ) Suatum
=i
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Basal plate
Neck
Pulp cavity
Like true teeth,the placoid scaleshave a baseof dentinewhich containsa pulp cavity filled with
connectivetissue. Both scalesand teethhave a spinousprocesscoveredby enamelwhich protrudes
through the skin.
Describethe direction (using anatomicalterms)in which rubbing the skin is roughest:
Tell what the terms epidermisand dermisrelateto:
Name the type of scalesembeddedin the skin of the shark:
Thesescales
are modificationsof teeth so they are called
When usedas sandpaper,sharkskin was once called
Use a scalpelto removea small sampleof skin from the back of the shark. Placethe sampleunder a
stereoscope
to seethe placoid scales.Make a sketchof the scalesbelow.
Verified
A preparedslide of a placoid scaleis availablefor viewing underthe compoundmicroscope.Draw what
you seebelow.
Preparedslide of the placoid scale
Stereoscopicview of the skin.
Masnification
(,
The shark'sbody is coloreddark gray aboveand much lighter, almostwhite, below. This distributionof
pigment (containedin melanophores)is referred to as counter-shadingand is common amongstaquatic
vertebrates.It tends to neutralize the effects of natural lights, which, coming from above,highlights the
back and castsa shadowon the underside.It tendsto makethe animal lessconspicuous,
Extending laterally, along the sidesof the body, somewhatnearerto the dorsal than to ventral surface,
look for a naffow light-coloredhorizontalstripe.Observecarefully along this line with a magnifying glass
and note the poresalong its length.This is part of the lateralline system.Belowthe skin, nervereceptors
called neurornastsrun along a lateral line canal with poresopening to the surface.They carry impulsesto
the centralnervoussystem.Thesereceptors,found only in fish and someaquaticamphibians,are sensitive
to the mechanicalmovementof water,to disturbancesin the water, and to suddenchangesof pressure.
They warn the sharkof vibrationsand movementsevenin murky water,wherevisibility is reduced. In the
areaof the headthe lateralline canalbranchesto form severalcommunicatinscanals.
Tell what melanophoresare.
Explain why counter-shadingis importantto the shark:
Give the purposeof the lateralline system:
On the diagrambelow, draw and label the lateralline. Use a pencil to shadethe diagramshowingthe
present.
amountof counter-shading
Note patchesof poresupon the headin the areasof the eyes,snout,and nostrils.Theseare the openings
of the ampullaeof Lorenzini, senseorganswhich are sensitiveto changesin temperature,water pressure,
electricalfields, and salinity. Pressfirmly upon the skin nearthe nares(nostrils).Note thejelly-like
materialyou have squeezedout of the pores.
ampullaeof Lorenzini
Tag the lateral line and ampullae of Lorenzini
Completed
Name the four stimuli sensedby the ampullaeof Lorenzini:
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Examine the head of the shark and note each of the following:
Rostrum - This is the pointed snout at the anterior end. This streamlinedtaperedtip at the anterior end
helps overcomewater resistancein swimming.
Nares - These are the openingsfor the external nostrils. They are located on the underside(ventral
surface)of the rostrum anterior to the jaws. Water is drawn into the naresto moisten the sensorycells of
the olfactory sac.
Water passesinto and out of the olfactory sac,permitting the sharkto detectthe odorsof the water. The
ability of the sharksto detectblood and injured flesh at greatdistancesfrom their sourceis legendaryand
is a major attractantand subsequentcauseof shark attacks.
Jaws- The openingto the mouth of sharksis alwayson the underside.The greatpowersof the shark's
jaws have beenretold by marinersfor generations.Recentlya testingdevice,the gnathodynamometer,
was
usedto measurethe force exertedby thejaws of a typical eight-foot shark.It was an extraordinary
eighteentons per squareinch!
On the diagram(s)below, label the rostrum. Tag eachof the following: rostrum and nares.
Verified
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External nails
Labial groove
Labial pouch
Head (ventrcl view).
Head (dotsal view)
Give the more commonnamefor the olfactory sense.
Tell what a gnathodynamometerdoes:
x
Use a magnifier to examine the teeth. They are sharp and
pointed. They are formed of the samematerial and
developsimilarly to the smallerplacoid scalesdistributed
over the shark'sentirebody. Besidesthe visible teeth,
severalrows of flattened teeth lie behind the upright set
readyto replacethem when worn out or lost. (View the
commerciallypreparedsharkjaw availablein class.) It
has been estimatedthat the sreat white shark has about
400 teeth.
In the spaceto the right, draw severalteethto show their
arrangementin the jaw.
Eyes-These are very prominentin sharks. A transparentcorneacoversand protectsthe eye. A darkly
pigmentediris can be seenbelow the comea. Its contractionand relaxationcontrolsthe amountof lieht
enteringthe eye. In its centeris the openingto the interior of the eyeball,the pupil.
Upper and lower eyelidsprotectthe eye.
Just insidethe lower lid, a membrane
may be seen,the conjunctiva. It extends
over the surfaceofthe eye to cover the
cornea.
On the diagramto the right, label the
come4 iris, pupil, and the conjunctiva.
Spiralces-These
large openingsposterior
and dorsalto the eyesare actually
reducedfirst gill slits in thejawed fish.
A pseudobranch,false gill, is a reduced
first gill which may be seenwithin the
spiracle.A fold of tissue,the spiracular
valve, permitsthe openingand closing
of the externalspiracularpore. The
spiracleservesas an incurrentwater passagewayleadinginto the mouth. Thus water can be brought in for
respirationevenwhen the shark'smouth is closedor when he is feeding.
Gill Slits - Most sharkshave five externalgill slits. They are locatedlaterally,posteriorto the mouth, in
front of the pectoralfins. Water taken in by the mouth is passedover the internal gills, oxygen is removed
and carbondioxide excreted.The water is then forced out to the extemal environmentby way of the gill
slits. The structureof the gills, their cartilaginoussupportand blood supply will be discussedlater in the
dissection.
Give the purposeof the spiracularvalve:
Give the function of the spiracles:
The spiraclesare usedwhen water is not able to enterthe shark's
How many external gill slits are found on your shark?
Relativesof the shark. such as ravs
and skates,that live on the bottom of the ocean,use the spiracle for water intake almost exclusively.
Why would this be true?
1
EndolymphaticPores- Look at the top of
the head betweenthe spiracleswith a hand
lens.You will see apair of tiny
endolymphaticpores,one on eachside of
the midline. They are continuationsof the
endolymphatic ducts which lead into the
inner ear which, in tum, servesprimarily
as an organ of equilibrium.
On the diagram to the right, draw in and
label the eye, a nare)a spiracle,an
endolymphaticpore, the mouth, and the
gill slits.
What doesequilibrium mean?
What doesequilibrium have to do with the inner ear?
Tag eachof theseon your shark: spiracle,endolymphaticpore, gill slits
Verified
Fins - The spiny dogfish sharkpossesses
two singledorsalfins, a caudalfin, and two pairs of ventral fins.
Dorsal Fins - The anteriordorsalfin is largerthan
the posteriordorsalfin. When sharksare seennear
the surfaceof the water,the telltale sign is the
triangularanteriordorsalfrn projectingominously
abovethe surfaceof the water.
A featurepeculiarto our specimen,the spiny
dogfish,is the presenceof two spines,one
immediatelyanteriorto eachdorsalfin. When
captured,thesesharkswill arch their backsand
attemptto piercetheir captorwith theselong sharp
spines.Besidesthe puncturewoundsthesecan
inflict, the spinesalso carry a poison secretedby
glandsat their base.The structuresand origins of
thesespinesare similar to thoseof the tiny dermal
placoid scalesand teeth. Becauseof the inherent
danger to students,the spinesare clipped by the
company that preparesthe sharks. The baseof
the spinescan still be observed.
"Well,somehowlhey knew we were-whoo! Our
dorsqllins ore slicking oul! lwonder how monyllmss
lholS screwed thlngs up?.
CaudalFin (Tail Fin) - This fin is divided into two lobes;the largerdorsal lobe, and smallerventral lobe.
Note that the taperingbody axis passesupwardsinto the dorsallobe. This type of tail is known as a
heterocercaltail, as opposedto the single-lobed,fan-shapedsymmetricaltail of the bony fish known as a
homocercaltail.
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PectoralFins - The asymmetryof the shark'stail fin createsa problem.As the tail is moved back and
forth, the larger dorsal lobe causesthe shark to be propelled forward and downward in the water. To offset
the downward tendency,the paired pectoral fins act to deflect water downward and thus provide the lift
neededat the crucial end to keep the shark moving in a horizontal direction.
Pelvic Fins - Thesepaired ventral f,rnsare located on either side of the cloacal aperture.They are different
in malesand females. Thoseof the femaleare undifferentiatedwhile thoseof the male are specializedfor
use in the transferof spermto the femaleduring copulationor mating.
Cloaca- This nameis given to the chamberon the ventral surfacebetweenthe pelvic fins. It receivesthe
productsof the intestine,the urinary and the genitalducts.The name,meaningsewer,seemsquite
appropriate.A closerlook within the cloacawill revealthe urinary papilla. Also visible, especiallyin
maturefemale specimens,are the abdominalpores.
Claspers- Males have stout,groovedcopulatoryorganscalled clasperson the medial side of their pelvic
fins. Fertilizationin the dogfish sharkis internal. During copulation,one of the claspersis insertedinto
the oviduct orifice of the female.The spermproceedfrom the cloacaof the male along the grooveon the
dorsalSurfaceof the claspertoward the female.
Associatedwith the claspersof the male are accessorystructuressuchas the siphonsand in some
specimenslateralspinesand ventral hooks may be presentnearthe end of the claspers.
Tell how many fins are found on the shark:
swimmins nearthe surface:
Name the frn that shows when sharksare
Describethe locationof the soineson
the dogfish shark:
Give the purposeof the
spines:
Name the two
lobesof the caudalfrn:
Give the purpose
of the pectoralfins:
Give the meaninsof
the word "cloaca":
Name the three systemsthat convergeat the cloaca:
Tell which sex has claspers:
Draw-in and label on the diagrambelow (at leastone) of eachof the fins:
Tag eachof thesefins or
anatomicalparts:
' - - - -
: J - - : . .
:
,
Anterior Dorsal Fin
PosteriorDorsalFin
Spine
Caudal Fin
PectoralFin
Pelvic Fin
Cloaca
Ifpresent: claspers
Verified
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The following color diagram shouldbe completedaccordingto instructionsgiven in class. Match each
part by color. TRACE EACH LETTER as you color the matchingname....
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Determinethe sex of your sharkby checkingthe pelvic fins for claspers.Only maleshavethesestrong,
grooved structures.They are used during mating to hold the female stationary.Try to observea shark of
each sex. The cloaca,the common chamberon the ventral side of the shark, is betweenthe two pelvic fins.
The cloacaservesas an exterioropeningfor the digestive,excretory,and reproductivesystems.
Male cloacal region (venttal view)
What is the sex of your shark?
Female cloacal region (venlrcl view)'
Now would be a good time to give your sharka
name! Can you come up with a good one? Write the namehere:
Now is a goodtime for a review......Completethe diagrambelow by supplyingthe namefor eachpart...
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GENERAL DISSECTION HINTS
The term "dissection"meansmore than merely cutting
your specimenapart.It is a refined methodof seeking,
exposing, identi$ring, and studying internal anatomv. It
helpsto helpsto bring into view structuresnot readily
seen.
The dogfish sharkis generallynot the first organism
dissectedby students.Most likely an earthworm,
starfish,or crayfishhas alreadybeenstudiedin
previouscourses.Basedupon the earlierexperiences,
more is expectedof the student,a betterdissection.You
will note that more difficult tasksare presented,such
as, exposingthe delicatebrain, embeddedentirely in
cartilage.
A cartilaginousskeletonas found in the sharkoffers
certainadvantages.It permitspenetratinga tissuethat is
ordinarily hard and bony. This requiresa certain
"Whol isthis?.. . Some kind ot cruel hoox?"
amountof skill, for cutting into the cartilagecan
damagenervesand other structuresineparably.The techniqueof slicing thin chips while holding the
scalpelhorizontallymust be practiced.A slip of the blademay undo hours of carefulwork.
Use your scalpelsparingly.In the handsof a novice a scalpelcan do irreparabledamageto your specimen.
Blood vesselsand nervesmay be cut, organsremoved,delicatestructuresdestroyedwithout realizingthe
extentof the damagecaused.Improperinitial dissectionwill renderthe later study of partsvery difficult.
Rely more heavily upon your dissectingneedles,your
blunt probe,flexible probe,and even your fingers. They
are especiallyhelpful in separatingmuscles,in tracing
blood vesselsand nerves,and in clearingaway connective
tissue that binds structuresto one another.
When using your scissors,advancewith the rounded,
blunt end,not the sharp,pointed end. Your
forcepsshouldbe strong,able to hold on to thick muscle,
yet hne enoughto graspnarrow nerves.It is advisableto
havemore than one type of forceps.Move organsaside
with your fingers or with a blunt probe.
'And here we are last summer off the coast of "'
Helen,is this Hawaiior Florida?"
Observethe dissectionsof other studentsin the class.
Often a betterpreserved,a betterinjected,or a larger
specimenmay reveal structuresnot seenin your shark.
This is especiallytrue in the study of the urogenital
system.If your animal is a male, observethe reproductive
structuresof a female specimenand vice versa.You are
responsiblefor learning the reproductive structureof both
male and female sharks.
i1
Basedon the description(s)in the aboveparagraphs,label eachof thesedissectioninstruments:
THE MUSCULAR SYSTEM
Many of the introductoryremarksconcerningthe muscularsystem,while concemedprimarily with the
dogfish shark,are equally true for the higher vertebrates.The musclesof Squalusare a good exampleof
the musculaturein primitive vertebrates.In the higher forms thesehave beenmodified by migrations,
splitting, fusion, or a combinationof factors.In the sharkthe natural groupsof musclescan be recognized,
identified and studiedin the adult, while in higher forms the original naturalmusclegroupscan only be
found in the embryo.
Skeletalmusclesenablethe body to move. They are involved in moving the entire sharkthroughthe water
as well as in moving individual visceralstructuressuchas the jaws and gill arches.
Most musclesare firmly anchoredto the skeletonat one end,the origin of the muscle,while the other end
is attachedto the skeletalelementto be moved, and is known as the insertion.The fleshy centralportion is
termed the belly. The ends of a muscle are attachedto the skeletonmost often by meansof a narrow band
of connectivetissuecalled a tendon.
As you dissect,locatethe origins and insertionsof the musclesstudied.Then free the musclefrom other
musclesand from the nervesand blood vesselsassociatedwith it. The fine, transparentconnectivetissue
which binds adjacentmusclesis deepfascia,while tougherand more fibrous superficialfasciaconnects
the skin to the musclesbelow. When the musclehasbeenfreed,pull it gently. This will duplicatethe
/s
muscle'snolmal contraction.Observewhich bonesor organsare moved and which remainrelatively
stable.
The action of a muscleresultsfrom its contraction.Musclesare usually arrangedin antagonisticpairs.
This meansthat while a musclewill causea structureto move in one direction,its antagonistwill cause
to move in the oppositedirection.
Basedon the descriptionabove,
label the diagram at right with
the following terms: muscle
belly, tendons,origin, insertion
Actions of musclesFlexion - to bend at a joint
decreasingthe angle at thatjoint;
examples:elbow or kneejoint.
Extension-- to straightena joint,
increasingthe angleat thatjoint.
Adduction - to move appendage
toward sagittalmidline; example:
lowering arms from shoulder
level to rest at sides.
Abduction -- to move appendageaway from sagittalmidline: example:raisingarms from rest at sidesto
shoulderlevel.
Rotation- to move a structureabouta point, example:turning headfrom sideto side.
The study of the sharkmusculaturewill be divided into threeaspects.We shall first study the major body
muscleswhich propel the fish throughthe water,then thoseof the gill (branchial)areaand the head,and
finally, thoseof the fins (appendicularmuscles).
Tell what skeletalmusclesdo for the body:
Musclesare bound to other musclesby
and skin is bound to muscles
by
Explain what is meantby "antagonisticpairs" concemingmuscles:
"Closing" the fingers of the hand is an exampleof
out is an exampleof
exampleof
; straighteningthem
bringing the handstogether,as if to clap, is an
; lifting your ann to shoot a basketball is
the "Beauty QueenWave" is an exampleof
t6
BODY MUSCULATURE
Removea sectionof skin in order to observetypical body musculature.Proceedas follows.
Make a very shallow incision into the skin at the mid-dorsalline, directly posteriorto the anteriordorsal
fin. Continue to cut caudally for about 6 cm. At eachof the two ends,cut the skin ventrally along the
sidesof the body till you reachthe mid-ventralline. Do not cut too deeplyfor you may destroythe
musclesyou wish to study.Use a blunt instrumentsuchas a probe,the handleof your scalpel,evenyour
fingers,to removethe sectionof skin whoseperimeteryou havejust cut. If the shark'sskin adheresvery
tightly to the underlyingmusculature,the useof a scalpelmay be necessary.
Completed
Identify the partsin your dissectionas describedbelow.
Myotomes- The musclesyou have exposedare composedof segmentstermedmyotomes.They are
arrangedrn a zigzag,"'W"-shapedpatternalong the entirelength of the animal'strunk and tail. The
myotomesare separatedfrom one anotherby connectivetissuepartitionscalled myosepta.The dorsal
portion is clearly separatedfrom the ventral portion by the horizontal(transverse)septum,a band of
connectivetissuebetweenthe musclebundles.The directionof the fibers of eachmyotome is longitudinal
on eithersideof the horizontalseptumand somewhatobliquenearthe more dorsaland ventral extremes.
l o n g i t u d i n a lb u n d l e
epihyoideus
eletogenous septum
levator palatoquadrati
l o n 6 i t u d i n abl u n d l e
v e n t r a ll o n 8 i t u d i n a bl u n d l e
Tag the following on the exposedmusclewall: myotomes,dorsallongitudinal bundle,
septum,laterallongitudinalbundle, ventral longitudinalbundle.
Verified
The samemusclebundlescan be observedin the cross-sectionof the body. Use your scalpelto make a
cleancross-sectional
cut, through the entirebody of the shark,cutting off the tail, directly posteriorto the
seconddorsalfin. This affords a view of the transverseas well as the lateral alrangementof muscle
bundles. (The tail on your specimenmay alreadybe partially severed....makea fresh cut cleanthrough
the bodyjust anteriorto this "old" cut.
Completed
/7
View the cross-sectionof the tail just posteriorto the posterior(second)dorsalfin.
notochord
l o n e i t u d i n abl u n d l e
lateralline
sePtum
skeletogenous
body cavity
l a t e r a l o n g i t u d i n abl u n d l e
v e n t r a l o n g i t u d i n abl u n d l e
linea alba
Tag eachof theseon the on the cross-section:dorsallongitudinalbundle, laterallongitudinalbundle,
ventral lonsitudinalbundle.
Completed
APPENDICULAR MUSCLES
In fish the patternof appendicularmusclesis very simple.The fins do not undergocomplexmovements.
The primary forward thrust is achievedby the movementsof the body and the tail. The fins are for
steeringand maintainingstability.
PECTORAL FIN - Removethe skin of one pectoralfin from both its ventral and dorsalsurfacesto expose
the musculaturecontrolling the fin. Also removesomeof the skin immediatelymedial to the fin (on the
bodv wall).
Completed
Flexor and Extensor(Adductor and Abductor, Depressorand Levator)- You will find a singleventral and
a singledorsalmassof muscleradiatingtoward the distal end of the fin. Theseare the pectoralflexor on
the ventralsurfaceand the pectoralextensoron the dorsalsurface.The ventral flexor depresses
the fin and
pulls it forward,while the dorsalextensorraisesthe fin and pulls it posteriorly.
PELVIC FIN - The musclesof the pelvic fin are somewhatmore complex than thoseof the pectoralfin. In
addition,in males,part of the pelvic fin is modified as a clasperfor the transferof spermto the female.
Removethe skin of one of the pelvic fins from both its ventral and dorsalsurfaces.Also removesomeof
the skin immediatelydistal to the fin (just as you did with the pectoralfin).
Flexor and Extensor(Adductor and Abductor, Depressorand Levator) -The musclemasson the ventral
surfaceof the fin, the flexor, may be divided into the proximal pelvic flexor muscle,and the distal pelvic
flexor muscle.The dorsalmusclemass,the extensor,arisesfrom two origins.
The musclesof the pelvic f,rnsof malesare fundamentallythe sameas in females.However, someportions
of the dorsaland ventral musclemassextendinto the male'sclasperas separatemuscles.
DORSAL FINS - Although thesefins are not ordinarily consideredappendicularor movable,they possess
radial musclesupon their sides.
/B
Tag eachof the following musclesyou havejust exposedon the fins: pectoralflexor muscles(ventral),
pectoralextensormuscles(dorsal),pelvic flexor muscles(ventral),pelvic extensormuscles(dorsal).
Completed
H e l pd i a g r a m . . . . . .
Ventral view of the shark's
muscles.
Meckel'scartilage
guadratomand
ib u laris
coracomandibu
lar
intermandibularis
ventralconstrictors
common coracoarcual
'il\I
ffitl II
o.6"$
t1
H e l pd i a g r a m . . . . . .
Dorsalview of the shark's
muscles.
chondrocranium
or oblique
lateralrectus
levator palatoquadrati
ouadratomandibularis
c r a ni o m a x i l l a r i s
piracle
epihyoi{eus
z
dorsalconstrictors
i nterarcual
s
flrx\
il11tr
i'i\i,N'
\\\\il
skeletogenous
septum
Iaterallongitudinal
ventrallongitudinal
a0
Tum your specimenventral side up. Make a mid-ventralincisionjust anteriorto the cloacalopening.Cut
through the skin and muscle in an anterior direction slightly to the right of the mid-ventral line. Continue
your cut to the coracoidbar of the pectoralgirdle. At that point use your scissorsand proceedwith the
blunt end to cut the skin and muscles laterally toward the right and to the left. Similarly, at the point you
beganthe dissection,nearthe cloacalopening,cut laterallyto the right and to the left. You havethus
exposedthe largebody cavity known as the pleuroperitonealcavity. Fold back the large flaps of body wall
you have cut and securethem.
gall bladder
Iiver (median lobel
I
/h't
P e c t o r a lf i n
I
II
rugae
liver (right lobe)
M i d - v e n tr aI
I
\
esophageal papillae
I
lilt e
bile duct
comon
I
I
pancreas (ventral
l_
f--
\ r
--
f
( i
I
\
f--
lobe)
duodenum
Cloaca
pancreas (dorsal lobe)
ileum
P e l v i nf r n
spiral valve
\
pyloris
cardiac region
of stoMch
pyloric region
of stomach
I.iver (left lobe)
spleen
mesentery
rectal gland
mesolecium
colon
Completed
rstum
PLEUROPERITONEAL CAVITY
COELOM - The coelom or body cavity of the sharkis divided into the largerposteriorchamber,the
pleuroperitonealcavity, and the smalleranteriorpericardialcavity which containsthe heart.The two
cavitiesare separatedby a partition.
PERITONEUM - A smooth,shiny membranewill be seenlining the inside of the body wall. This
membraneis the parietalperitoneum.The membranecoveringthe surfaceof the visceralorgansis the
visceralperitoneum.As you move someof the visceralorgansto the side,you will seethat they are
suspendeddorsallyby a double membraneof peritoneumknow as mesentery.Different sectionsof
mesenteryhavevariousnamesindicatingthe types of organ suspended.
What is a coelom?
Give the namefor the coelom in the main body of the shark.
Name the materialthat "holds" the organsin place.
Tag eachof the following: coelom,pleuroperitonealcavity, parietalperitoneum,visceralperitoneum,
mesentery
Completed
2 i
The HELP DIAGRAM below will help with locatingthe intemal organs.
3
4
5
6
7
8
I
34
35
36
37
38
10
1 a
I I
10
39
1t
13
14
15
40
^4
TI
A2
.!
16
17
18
19
20
21
22
23
24
25
26
27
2
l a
29
3031
32
z.
43
47
48
I
50
51
52
52
53
54
|. Rostrum
2. Nostril
3. Mouth
4. Anterior branch of ventral aorta
5. Internal gill slit
6. Cill
7. External gill slit
8. Ventricle
9. Atrium, or auricle
10.Testis
l l. Pectoral fin
12. Bileduct
13. Call bladder
14. Hepatic artery
15. Hepatic portal vein
16.Kidney
1 7 . M e s o n e p h r i c ,o r W o l f f i a n d u c t
18. Coeliac artery
19. Dorsal aorta
2 0 . P o s t e r i o rc a r d i n a l v e i n
2 1 . P a n c r e a t i c o - m e s e n t e rai cr t e r y
22. Opening of bile duct
23. Ventral pancreas
2 4 . C a s t r o s p l e n i ca r t e r y
2 5 . S u p e r i o r m e s e n l e r i ca r t e r y
26. Lateral abdominal vein
27. Inferior mesenteric artery
28. Seminalvesicle
29. Large intestine
30. Sperm sac
3l . Cloaca
32. Urogenital papilla
33. Pelvic fin
34. Afferent branchial artery
35. Ventral aorta
36. Conus arteriosus
3 7 . P e r i c a r d i a lc a v i t y
3 8 . T r a n s v e r s es e p t u m
3 9 . P a p i l l a eo f s t o m a c h
40. Median lobe of liver
41. Left lobe of liver
42. Rugaeof stomach
43. Cardiac stomach
44. Castric artery
45. Dorsal lobe of pancreas
46. Pyloric stomach
4 7 . A n t e r i o r s p l e n i cv e i n
48.S;rtsgn
4 9 . A n t e r i o i . . t s e n t e r i cv e i n
5 0 . P o s r e r i o r i n t e s t i n a lv e i n
5 1 . R e c t a lg l a n d
52. Small intestine
53. Spiral valve
54. Abdominal pore
55. Clasper
33
?z
This HELP DIAGRAM showsa more detailedview of the digestivesystemand associatedorgans. Look
over it beforeyou beginthe digestivesystem....
*J
visceral pericardi
parietalpericardium
pericardial cavity
transverseseptum
coronaryligament
falciform
left liver lobe
right liver lobe
gallbladder
P.:r-
hepatoduodenalligament
tic ligament
ventrallobeof pancreas
mesointestine
duodenum
dorsallobe of oancreas
valvularintestine
parietalperitoneum
mesorectum
rectalgland
cloaca
urinaryvesicle
FIGURE5.4. Digestiveorgansand associatedstructuresof the coelom,ventral
view
.of a femalespecimen.The tiver lobesare spreadlaterallyand the intestineis pushedto
the right lateralside.The valvularintestinehasbeencut to revealthe internal
spiral valve.
Z3
LIVER - The largestorgan lying within the pleuroperitonealcavity is the liver. Its two main lobes,the
right and left lobes,extendfrom the pectoralgirdle posteriorlymost of the length of the pleuroperitoneal
cavity. A third lobe, the median lobe, is much shorterthan the others, and as the name indicates,is located
medially. Locatethe elongatedsac,the greengall bladderalong the right edgeof the medianlobe. The
common bile duct extendsfrom the anterior portion of the gall bladder to the duodenum.
The greatbulk of the liver can be visualizedwhen comparedto other organs.A giant 20-foot basking
sharkwhich weigheda total of 13,850poundshad a 1,850-pound
liver. The liver is rich in oil. This is the
form in which the sharkstoresenergy,not as fats. The oil's specificgravity is also responsiblefor giving
the sharka limited amountof buoyancy,althoughit cannotkeep him afloat as doesthe swim bladderof
bony fish.
ONE of the enzymesmadeby the liver is calledbile. Bile helpsto emulsifu (breakdown in to small
droplets)fats. The bile is madeby the liver, storedin the gall bladder,and transferredto the intestines
throughthe commonbile duct. Gall stonesdevelopin the gall bladderwhen the bile (a gooeygreen
('rock"-gall
liquid) precipitatesand forms a solid
stonesare a common problem in our area!
Tag eachof these: left lobe of the liver, right lobe of the liver, medial lobe of the liver, gall bladder,
commonbile duct
Completed
ESOPHAGUS--Movethe large lobesof the liver laterallyto revealother organsof the body cavity. You
will seea thick musculartube extendingfrom the top of the cavity at the mid-line posteriorlytoward the
left. This is the esophagus,or food tube from the mouth to the stomach.It passesthroughthe transverse
septumto connectthe oral cavity and pharynx with the stomach.
STOMACH -- The esophagusleadsinto the "J"-shapedstomach.The upper portion, the cardiacregion,
continuesas the main body, and endsat the duodenalend. The left-handouter borderof the stomachis
calledthe greatercurvaturewhile the right-hand,inner border is the lessercurvature.Dorsally the stomach
is supportedby a membrane,a derivativeof the mesentery,the mesogaster(greateromenturn).Another
membrane,the lesseromentum supportsthe stomachventrally.
Cut the stomachopen along its long axis. Note its contents.It will generallyconsistof partially digested
remainsof fish, squid,or other seaanimals. List any contentsfound in the stomachbelow:
STOPand get checked-offso you will know what to do with the contents. Verified
Wash out the inside of the stomachunder slowly running water.Note the mucosa,the inner lining
membrane.The longitudinalfolds, the rugae,help in the churningand mixing the food with digestive
juices. A circularmuscularvalve, the pyloric sphincter,is locatedat the posteriorend of the stomach.It
regulatesthe passageof partially digestedfood out of the stomach.
Tag eachof the following: greatercurvature,rugae,pyloric sphincter. Completed
DUODENUM - A short "fJ"-shapedtube,the duodenum,the first portion of the small intestine,connects
the stomachto the next part of the alimentary canal. The bile duct from the gall bladder entersthe dorsal
surfaceof the duodenum.
z r_i
PANCREAS - Ventral to the duodenum and partially obscuring it is the whitish glandular tissue of the
pancreas.The greaterportion of the pancreasis not seenuntil one examinesthe dorsal surfaceof the
stomachand duodenum.Here the dorsal elongatedsegmentof the pancreasmay be found. Connectingthe
dorsaland ventral lobesof the pancreasis the isthmus,a slenderband of pancreatictissue.The secretions
of the pancreasenter the duodenum by way of the pancreaticduct.
SPLEEN - Near the posteriorend of the stomachfind the dark, triangular-shapedspleen.Although not a
part of the digestivesystembut the lymphatic system,it is closely associatedwith the digestiveorgansof
vertebrates.The spleenstores"extra" blood cells the body can draw on when needed. It is sometimes
ruptured in auto accidentswhen the driver slamshis/her gut into the steeringwheel (wear your seat
belt!!!!) andmustbe removed.
Tag eachof these: duodenum,bile duct (again),pancreas,spleen. Completed
VALVULAR INTESTINE - This second,and much larger,portion of the small intestinefollows the
duodenum.Its outer surfaceis markedby rings. This hints at the contourto be found within. Cut away the
outertissueof this portion of the alimentarycanal. Washout the contents.You will seea symmetrical
spiral shapewithin, the spiral valve. It addssurfaceareafor digestionand absorptionto an otherwise
relatively shortintestine.In higher vertebrates,increasesin surfaceareaareaccomplishedby meansof
coiling and projectingfinger-like villi.
Completed
COLON - This narrowedcontinuationof the valvular intestineis locatedat the posteriorend of the
pleuroperitonealcavity. If the end of the colon hasbeenevertedthrough the cloacalopening,pull it back
into the body cavity.
RECTAL GLAND - A slender,narrowed,finger-like structure,the rectal gland, closedat one end, leads
into the colon by meansof a duct. It hasbeenshownto excretesalt (NaCI) in concentrationshigher than
that of the shark'sbody fluids or seawater. It is thus an organof osmoregulation,regulatingthe shark's
salt balance.
CLOACA * The last portion of the alimentarycanalcollectsthe productsof the colon as well as the
urogenitalducts.This catch-allbasin leadingto the outsideby meansof the cloacalopeninghasrightly
deservedits namewhich meanssewer. In higher vertebrates,separateexits exist for the rectum(anus),for
the urinary bladder(urethra),and for the reproductivesystem(vagina).
ABDOMINAL PORES-- The coelomic cavity of higher vertebratesis closedand has no direct connection
with the outside. In the shark,however, apair of abdominalporesmay he found posterolateralto the
cloacalopening. Passa blunt probe throughthe poresto confirm the connectionbetweenthe coelonnand
the outside.In somespecimensthe lips of the pore may have grown together.Their function hasnot yet
beendetermined.
Completed
Tag eachof the following: colon, rectal gland,cloaca,abdominalpores
Completed
NON-DIGESTIVE ORGANS - Severalorgans,not part of the digestivesystem,may be seenin the
pleuroperitonealcavity. Most are part of the reproductive and genital systems. The gonads(testesor
ovaries)may be found by moving the liver and digestiveorgansto one side.They are locatedin the
2s
anterodorsalportion of the body cavity. The kidneys are dark elongatedstuctures, running the length of
the body cavity on either side of the mid-dorsalline. We will visit theseorganslater in the dissection.
Name the largestorgan of the pleuropertinealcavity:
How many lobesdoesit
Name the greenstoragebag found on the medial lobe:
have?
Name the duct that carries bile from the liver to the duodenum:
Describethe function of oil in the shark'sliver:
Describethe function of bile:
Qor."r
Whatdoesbile fu whenit precipitates?
Give a more commonnamefor
the esophagus:
Tell whererugaeare locatedand what they do:
Name the first portion of the small intestine
Name the body-systemthe spleenbelongsto:
Give the purposeof the spleenin the
body:
Tell what the rectal gland does:
Tell what the word "cloaca" means:
ORAL CAVITY AND PHARYNX
Although the mouth, the oral cavity, and the pharynx of the sharkserveas passageways
for food, they play
a more activerole in respiration.
RESPIRATION - Water taken into the mouth and pharynxpassesover the gill filaments,throughthe gill
slits, to the outside.During this process,oxygen is removedand transportedinto the circulatorysystem
and carbondioxide is releasedfrom the blood at the sill lamellaeand exits via the sill slits.
"c'mon,c'monlYoiJiS qultclrcllngtholobleond
"Beor!Beot!"
2G
With the shark lying ventral side up, insert the blunt blade of a stronq
pair of scissorsinto the right corner of the shark'smouth. Begin cutting
posteriorlythroughthe angleof the jaws acrossthe gill slits as far back
as the pectoral girdle. Cut acrossthe ventral musculatureto lay the
entire preparationflat. Your shark should look like the specimen
shownbelow....
Completed
New cut
Q r i g i n a lc u t
The Oral Cavity
BUCCAL CAVITY - The proper name for the mouth.
TEETH - Thesetriangularsharpstructuresare arrangedin severalrows beginningat the outer edgesof the
upperand lower jaws. They are similar to the dermal denticlesfound on the skin of the sharkin their
structureand development.Behind the visible rows of teethare other rows within the mucosa,usually
folded downward ready to replace any lost. It has beenestimatedthat the mouth of the great white shark
may contain400 teeth! CAREFULLY rub your finger acrossthe rows of teeth-they're sharp! Observe
the'Jaws" sectionof a larger shark (if it is availablein class).
TONGUE - The tongueof the sharkis different from the true tongueof higher vertebrates.It is practically
immovable,without musclesunder the epithelium.It is supportedanteriorlyby the basihyalcartilageof
the hyoid arch and posteriorlyby the pharyngealarch cartilages.Thesecan be palpatedby the fingertips.
PHARYNX - The pharynx is the portion of the alimentarycanalposteriorto the hyoid arch betweenthe
gill slits. Posteriorlyit narrowsto form the esophagus.
SPIRACLES-- The spiraclesare openingsin the anteriorroof of the pharynx, in its dorsolateralwall. The
shark can bring water into its pharynx to the gills by way of the spiracleseven when its mouth is closed.
Passa blunt probe into one spiracleand note where it exits.
Completed
21
GILLS - The gills are the respiratoryorgansof
the shark.They are composedof gill lamellae,
blood vessels,and supportingcartilaginous
structures.
As you look at the pharynx you will seefive
internalgill slits. They lead into cavitiescalled
gill pouches,which lead to the outsideby
externalgill slits. The gill slits are supported
by cartilaginousgill archesand guardedby
small cartilaginouspapillae-likegill rakers
which act as strainersto prevent food particles
from leavingthe pharynx through the gill slits.
Give the propernamefor the mouth:
spiracle
internal
gill slits
Tell wherethe pharynx is located:
gill rakers
Tell what the spiraclesdo:
Give the function of sills:
Tell what gill rakersdo:
Tag eachof the following: externalgill slit,
intemal gill slit, interior spiracle,esophagus,
tongue,buccalcavity
Completed
external gil slit
THE CIRCULATORY SYSTEM
The circulatorysystemis involved in transportingsubstances
to and from the body cells. It consistsof the
heart,the arteries,veins, sinuses,capillaries,and the blood.
THE PERICARDIAL CAVITY - The pericardialcavity is the upper portion of the coelom,the body
cavity. It is much smallerthan the lower coelom,the pleuroperitonealcavity. It is locatedanteriorto the
transverseseptumand containsthe heartand the major blood vesselsleadingto and from the heart.
Placethe shark ventral surfaceupward and "flip" the lower jay so that it is back in its normal anatomical
position.Locatethe pectoralgirdle. Removethe skin anteriorto the coracoidbar, till the edgeof the lower
jaw (Meckel'scartilage).Removethe ventral musculaturein this area.A membranewill be found covering
a triangular cavity, the pericardial cavity. Remove the membraneto exposethe heart and some of its major
blood vessels.The heart is "roughly" in a line that forms when you connectthe two anteriorgill slits (see
the picture on the next page).
Completed
z8
I
I
conusa rteriosus
l
\
\
\
t
\
pericardialcavity
Iatri
\
artery
ur
septum
transverse
tium
Locateand identify all of the parts listed below.
PERICARDIUM - This is the membranelining the inner walls of the pericardialcavity. It is known as the
parietalpericardium.The layer of membranecoveringthe heartis the visceralpericardium.It is fusedwith
the heartand cannotbe peeledoff. At the upper and lower bordersof the heart,observewherethe parietal
and visceralpericardiajoin and are continuouswith one another.
THE HEART - The sharkheart is composedof four distinct continuoustube-like chambers.Blood is
passedfrom the more posteriorend anteriorly in sequence,from one chamberto the next. The four
chambersare:
I . sinusvenosus; 2. atrrum 3. ventricle; 4. conusanteriosus
SINUS VENOSUS - This is the most posteriorof the four chambers.Deoxygenatedblood from the entire
body returnsfirst to this chamberof the heart.Lift the main portion of the heartand observea broad,thinwalled, flattened,almosthorizontal,sac-likestructureextendingthe width of the pericardialcavity. Its
baselies upon the transverseseptum.
ATRIUM - This chamberis anteriorand dorsalto the sinusvenosus.It is also thin-walled with two lateral
bulging lobes.It receivesblood from the sinusvenosus.
VENTRICLE - This most ventral part of the heart is first seenupon exposingthe pericardialcavity. It is
an oval-shaped,thick-walled,muscularsac,lying ventralto the atrium. Pairedcoronaryarteriesmay be
seenon its ventral surfaceas well as on the conusarteriosus.
CONUS ARTERIOSUS - A thick, muscular,tubular structurewhich originatesfrom the anteriorsurface
of the ventricle.It extendsanteriorly to the upper end of the paricardialcavity.
Note: Unlike the heart of higher vertebrates,the heartof the sharktransportsdeoxygenatedblood only.
The processof oxygenationtakesplace at the gills, from whereblood passesto the entirebody without
first returning to the heart.
In the shark,blood flows from the
Name the "receiving" chamber of the shark heart:
end of the heart to the
end.
Name the "pumping" chamber
of the sharkheart:
2\
Completethe following color diagramto help you becomefamiliar with the balanceof the circulatory
systemof the shark.. ..
GIRGULATORY
SVSTENfl.
HEARTSINUSVENOSUSO
ATRIUftfi'
VENTRIGLE"
G@NUS
ARTERI@SUS,
VENTRALA@RTA,
AFH BRANGHIALA",.
EFRBRANGHIAL
A"'
DORSALA@RTA,,
SUtsGLAVIAN
A"=
GELIAGA""
[L[AGA""
GAUDALA"',
P@STGARDINALV""
ANT GARDINALV""
HEPAT'IG
PORTALV"u.
HEPATIG
V""
JUGULARV""
G@nfinfiON
GARDINALY.u'
Is the blood that goesthrough the shark'sheartoxygenatedor deoxygenated?
Wheredoesthe blood pick up oxygen?
"My marriageis in trouble, Barbara.You
ever tried
communicatint
with a hammerheadl"
3o
THE UROGENITAL SYSTEM
The urinary and genital systemshave distinct and unique functions. The first, the removal of nitrogenous
wastesand the maintenanceof water balance;the other, the reproduction of the species.However, due to
their similar developmentalorigins and the sharingof common structures,they are usually consideredas a
single system.
The shark kidney and its ducts are quite different from those in higher vertebrates.The relationship
betweenthe urinary and genital structuresis also quite different. Male and female sharksdiffer in their
urinary as well as in their genital systems.The urogenitalsystemof the shark illustratesa simpler stageof
development.
Mature specimensmake for the best
dissectionssincethe entireurogenital
systemwill be fully developed.In immature
specimensmost structuresare
undifferentiated.If your animal is a male,
you are alsoresponsiblefor studyingand
knowing the urogenitalsystemof an adult
female shark,and vice versa.
Exposethe pleuroperitonealcavity. Remove
almostthe entireliver exceptfor its anterior
end. Cut the esophagusabout a half inch
from its entry into the body cavity. Then cut
the colon about one and a half inches from
its posteriorend.Freethe alimentarycanal,
pancreas,and spleenfrom their mesentery
and vascularconnectionsand remove
entirely from the body. This will revealthe
urogenitalstructures:gonads,kidneys,and
associatedducts.
The diagram to the right shows what you
will REMOVE (as describedabove).
esoPnaSus
body
l e s s e rc u r v a t u r e
S r e a l e rc u r v a t u r e
pvrc
duodenum
spirar
v a l v u l a ri n t e s t i n e
Completed
We shall study the female first, then the
male. This will be followed by a discussion
of fertihzation and developmentin the
dogfish shark.
rectal gland
A help diagramis on the next pageto help you sex your shark....
Identifv the sex of vour shark:
__)I
{
l
IMMATURE
IMMAfUBE
MA TURE
I
ii
.t
Mesorchium
Effercnt ductules
Mesonephilc duct
!
i!
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//
ii
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i
,
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Seminal
vesicle
i/
Accessorymesonephricduct
Spetm sac
\
,'/'
Urcrcctal shelf
Urogenital
papilla
Male utogenital system
Female Ltrogenilal system
FEMALE
KIDNEYS - The kidneys are flattened,ribbon-like, darkly coloredstructureslying dorsallyon either side
of the midline, along the entire length of the pleuroperitonealcavity. In females,the upperportion of the
kidney is nonfunctional; the formation of urine and the removal of wastestake place in the lower portion.
OVARIES - Look within the anteriorpart of the pleuroperitonealcavity, dorsalto the liver. Locatetwo
cream-coloredelongatedorganson either side of the mid-dorsalline. The shapeof the ovarieswill vary
dependingupon the maturity of the specimen.In immaturefemalesthey will be undifferentiatedand
glandular in appearance.In mature specimensyou may find two to three large eggs,about three
centimetersin diameter,in eachovary. When thesebreakthe surfaceof the ovary, upon ovulation,they
enter the body cavity and are moved into the oviducts.
OVIDUCTS - The oviducts are elongatedtube-like structureslying dorsolaterallythe length of the pleuroperitonealcavity, along the sidesof the kidneys.In maturespecimensthey are more prominent. The distal
half of the oviduct is enlargedto form the uterus.Traceone oviduct anteriorly.It passesdorsalto the
ovary, then curvesventrally in front of the anterior portion of the liver.
sa
UTERUS - The posteriorhalf
of the oviduct becomes
enlargedand is known as the
uterus.Here the fertilized eggs
developinto embryos.Upon
completingtheir period of
gestation(closeto two years)
the young are ready to be born.
ovuian artery
7'-^""
parietal peritoneum
CLOACA - This opening
servesfor the elimination of
urinary and fecal wastesas well
as an aperturethrough which
the young "pups" are born.
Give the two functions of the
urogenitalsystem:
Name the liquid material
POSlenor
meSenlefl c artery
producedas waste by the
kidneys:
Give the gestationperiod for
the shark:
Give the namefor young
urinary papilla
il ii,"l
,,1
sharks:
MALE
KIDNEYS - The kidneys of the male are essentiallythe sameas thosejust describedin the female.The
posteriorportion is involved in the manufactureand transportof urine, its role quite similar to that in
females.The main differencelies in the anteriorportion of the kidney, which in femalesis functionless,
but in malesis an activepart of the reproductivesystem.
TESTES- Pairedtesteslie nearthe anteriorend of the pleuroperitonealcavity,dorsalto the liver, adjacent
to the anterior endsof the kdneys.
EPIDIDYMIS - Spermpassto the anteriorend of the kidneys. This portion of the kidney is known as the
epididymis.
DUCTUS DEFERENS (WOFFIAN DUCT) - After passingthrough the epididymis the spennenterthe
ductus deferensand passposteriorly toward the cloaca.In mature male specimensthe ductus deferensmay
be seenon the ventral surfaceof the kidneys as a pair of highly coiled tubules.The kidney right below the
epididyrnisis known as Leydig's gland.Here the secretionfrom the testesis modified as a milky thick
fluid analogousto the seminal fluid of higher vertebrates.
33
SEMINAL VESICLE - The posterior
portion of the ductus deferenswidens
and straightensto form the paired
seminalvesicles.If you can locate
them, nick the surfaceof one with a
pin and observea thick white fluid
oozing out. This is the seminalfluid.
posterior cardinal sinus
left tesl
SPERM SACS - Thesepaired sacsat
the posteriorendsof the seminal
vesiclesreceivethe seminalsecretions.
/,
celiac artery
posterior-"2
CLOACA - As in the female,this
structurereceivesthe rectal wastesas
well as the genital and urinary products.
mesorchium
i'ir,\;li
'',i
"
CLASPERS- They are modified
extensionsof the medial portions of
the pelvic fins. They are insertedinto
the female'scloacaduring copulation.
ClasperTube -- The finger-like
clasperseachhave a dorsalgroove,
the claspertube (spermaticsulcus)
that carriesthe seminal fluid from the
cloacaof the male to the cloacaof the
femaleduring mating.
Leydig's gland
anterior mesenterlc artery
lieno8astricartery
mesenterrcartery
o"$
s e m i n a lv e s i c l e
accessoryurinary duct
It was originally thought that the
siphonsacwas frlled with seawater,
which during copulationwas ejected
along the claspertube to help propel
the spermtoward the female.It was subsequentlyshown,however,that the siphon sacssecretelarge
amountsof mucouswhich may lubricatethe claspersand contributeto the seminalfluid.
FERTILIZATION AND DEVELOPMENT
We havealreadypointed out that fertilization in the dogfish sharkis internal,usually taking placewithin
the oviduct.The fertilized eggscontinueto move posteriorlvtoward the uterus. Here the young develop.
As they grow they are attachedto the egg, now known as the yolk sac,by meansof a stalk.
IF IN LUCK, a developing"pup" might be present. Note the externalyolk sacconnectedto the
alimentarycanal. During its period of gestation,which is nearly two years,the yolk is slowly absorbedby
the shark"pup." At about25 centimetersin length the externalyolk sachas beencompletelyabsorbed.At
birth the young are about23 to 29 centimeterslong.
39
This type of development,where the young are born as miniature adults but have received hardly any
nutrition directly from the mother'suterus,is known as ovoviviparous.By contrast,humandevelopmentis
viviparous.
Completethe following color diagramto review the partsof the reproductiveand excretorysystems.....
NfiALEK[DNEY^
TESTilS'
EFFERENT
DUGT.
FENflAUEKIDNEY^'
URINARVDUGT^
UR[N.SINUS'
EPilD[DYSfl[So
AR@HINEPHRIG
DUGTU
@VARV"
@V[DUGT'
VESilGLE'
SENNINAL
SPERnflSAG.
UROGENMAL
SINUSGLOAGA
GLASPERS,
SHELLGL"o
UTERUS'
GL@AGA.,
ANTEFIOF
OSTlUlvl
ESOPHAGUS
ESOPHAGUS
ANTEFIOR
KiDNEY'I-
/
BODYWALL
(CUT)
VENTFAL
SUFFACE
POSTERIOR
POSTEFIOR
3S
THE NERVOUS SYSTEM
The nervoussystemfunctions in communication betweenthe various parts of an organism and between
the organism and its external environment. It consistsof the central nervous system;the brain and spinal
cord, and the peripheralnervoussystem;the senseorgans,cranial and spinal nerves,and their branches.
THE BRAIN
The advantages
in studyingthe shark'sbrain include:
-- The skull is composedof cartilage,not bone.This makesthe brain accessibleto the scalpel'sblade.
-- The brain of the sharkis relatively large.Thus,the grossanatomyof smallernervesand structuresmay
be observed.
-- It illustratesa lower level of developmentamongvertebrates.Comparativestudiesof different vertebratesrevealever-increasingcomplexity in the structureof the brain, especiallyin the cerebralregion.The
basicarchitecturalplan of the vertebratebrain and cranialnervesis, however,alreadylaid out.
IT IS VERY IMPORTANT THAT YOU READ THE NEXT FEW PARAGRAPHS AND FOLLOW
THE DIRECTIONS VERY CAREFULLY OR YOU WILL DESTROY THE BRAIN. TAKE YOUR
TIME!!!!!
The techniqueof dissectionof the chondrocraniumis uniqueto cartilaginousf,rsh,for unlike bone,the cartilage permitsthe use of a scalpelin exposingthe brain. First removethe skin from the dorsalsurfaceof
the headfrom the rostrum posteriorlyto the first gill slit. Continueremoving the skin ventrallyto the level
of the eye and the spiracle.
Make all of your cuts of the chondrocraniumhorizontaland shallow in a shavingmotion. This is your best
guaranteethat you will not be injuring delicatebrain tissueor cranial nerve fibers. The cartilageis
transparentup to a depth of aboutone millimeter. Therefore,cut very thin horizontalchips of craniumno
more than one millimeter thick. The thin chips may be broken loose and removedwith forceps.
Your scalpelbladesare extremelysharpand the soft delicatenervetissue,unlike the cartilage,offers
virtually no resistance.Begin the careful removal of the cranium on the left side antero-dorsallyand work
your way posteriorly.As was pointed out, the inner ear on this sidewill be destroyedin order to seethe
brain and cranial nerves lying beneathit.
A help diagramon the next page showswhat your dissectionshouldlook like when completed.
3G
chondrocranium
olfactory sac
neryus terminalis
c e r e b r ahl e m i s P h e r e
i n f r a o r b i t at rl u n k( V ,V l l )
superficialopthalmictrunk (V Vll)
s u p e r { i c i a lo P h t h a l m i c n e r v e
optic neNe (ll)
epithalamus
trochlear nerve (lV)
optic lobe
deep ophthalmic nerue
o c u l o m o t o rn e r v e( l l l )
c o m m o ns t e m( V , V l l , V l l l )
mandibular newe
auricle of cerebellum
ducl
h y o m a n d i b u l at r u n k ( V ll )
membranous labyrinth
nerve (lX)
ossopharyngeal
fourth ventricle
medulla oblongata
vatus nerve (X)
Brain exposed
Beginningat the anteriorend of the brain, locatethe olfactory lobes (smell) and the cerebralhemispheres
(the "thinking" portion of the brain). Locatethe optic lobes(vision)just anteriorand beneaththe
cerebellum(coordinatesthe body for movement,etc.). The medulla oblongata(controlsinvoluntary
actionssuchas breathing,digestion,etc.) can be locatedposteriorto the cerebellumif you have donea
goodjob with your dissection.
Tag the following: cerebrum,cerebellum
Completed
Removethe brain from the bodv of the shark.
Completed
?,Y
' v l
Completethe following color diagramto help you betterunderstandthe anatomyof the neryoussystem....
NERVOUSSVSTIENfi.
NNETENGEPHAL@NBRAINGEREBELLUftfi"
TELENGEPHAL@N*
BULB"
NNYELENGEPHAL@N
@LFAGT@RV
@BL@NGATAGEREBRALHENMISPHERE' NfiEDULLA
D|ENGEPHAL@NSPINALG@RD.
EPMHALANNUS
PERIPHERALNERVOUS
INFUNDIBULUftfl,
svsTEnfi.
PffiUffiARYGL"^
GRANIALNiERVES'
NNESENGEPHALON
SPINALNERVES.
LOBE..
@PTroG
OCFSA.
THE EYE
The eye of the sharkis very similar to the eye of higher vertebrates.The one major differenceis its
methodof accommodationin focusingfor nearand distantobjects.While in the higher forms this is
accomplishedby changingthe shapeof the lens,in the sharkit is done as in most camerasby moving the
lens further or closerto the retina.
The dissectionwill be done in two stages.First,
the eyeballwill be removedfrom its socket(the
orbit) in orderto view someof the muscles,
nerves,and supporting structuresof the orbit and
the extemal parts of the eyeball. Then we shall cut
into the eye to view its internal structure.
EYELIDS - Although most fish have no eyelids,
the sharkdoespossesseyelid folds. However,
unlike the eyelidsof the higher vertebrates,those
of the shark are immovable.
CONJI-JNCTIVA - A thin transparentmembrane
which coversthe outer surface of the eye. It folds
Ciliary body
Suspensoryligament
Vitreouschamber
Conjunctiva
Cornea
Pupil
Lens
Anterior
chamber
Posteriorchamber '
Eyeball(sagittalsection).
s3
at its outer edgeand passesunder the lid.
Make a circular cut around the edge of the eye at the junction of the conjunctiva and eyelid to separatethe
eyeballfrom its orbit. Removesomeof the dorsalchondrocraniumover the eye. You will exposethe six
extrinsiceye muscles. Cut the eye musclesand nervesneartheir insertionson the eyeball.Lift out and
remove the eyeball from its orbit.
Completed
EYE MUSCLES - Of the six extrinsic eye muscles,two originatein the anteromedialorbital wall; these
are the obliquemuscleswhich pull the eye diagonally.The other four originatein the posteromedialwall
of the orbital wall; theseare the rectusmuscleswhich pull straightback on the eyeball.
OPTIC NERVE - A thick white stump,the optic nervemay be seenexiting the back of the eyeball.It
emergesjust ventralto the site of the insertionof the medial rectusmuscle.
We arenow readyto observethe eyeballitself, both externallyand internally. First observethe external
features,then cut through the eyeballabouthalfivay betweendorsaland ventral surfaces.This will expose
the inner structures.
SCLERA - This is the tough white fibrous outer coat of the eye.At placesit is madeevenmore firm by
cartilageembeddedin the sclera.
CORNEA - At the front of the eye this tough coat becomestransparentas the corneaof the eye.The
conjunctivalies over the cornea.
CHOROID - This is the vascularblack pigmentedmiddle layer of the eye. Laterally, it is fusedto the
retina.The darkly pigmentedlayershelp in absorbinglight within the eye.
RETINA - This is the multi-layeredsensorygray-whitecoloredmembrane.The rods and coneswhich receive light stimuli are locatedhere.The optic nerve leavingthe eye is a continuationof the light receptor
cells in this membrane.
PUPL - This round hole behind the corneais an openingin the iris of the eye. It can dilate or constrictto
allow more or lesslight to enter.
IRIS - A pigmentedanteriorextensionof the choroid layer.In its centeris the pupil. The iris regulatesthe
size of the pupil.
VITREOUS CHAMBER - The main cavity of the eyeballcontainsa gelatinous,transparentsemi-solid
calledthe vitreoushumor. It gives shapeto the eyeballand preventsit from collapsing.
Removethe lens from the eye. It will look like a small marble.
You might want to try bouncing it on your lab table!
Completed
OLFACTORY ORGAN
This is the shark'sorgan of smell. Note the location of the extemalnares(nostrils).Each is divided into
two openings:the lateral one, an incurrent aperture,and the medial one, an excurrent aperture.Theseare
partially separatedby a flap of skin that regulatesthe flow of water into and out of the nares.There is no
connectionbetweenthe nasal area and the mouth or oral cavity.
s1
Make a transversecut acrossthe snout through the centerof one of the nares. Attempt to locate the
following:
OLFACTORY SACS - Thesebulb-like structures,sphericalin shape,containa seriesof radial folds
which increasethe surfaceareacalled olfactory lameellae.Seawater taken into the naresis passedover
thesesensoryareas.
OLFACTORY BULBS -- Theseare a paired anteriorextensionof the brain leadinginto the posteriorend
of the olfactory sacs.
LATERAL LINE SYSTEM
This sensorysystemis only found in fish and amphibianlarvae.
LATERAL LINE CANALS - It is a systemof sensorycells and canalsunder the skin which respondsto
mechanicalmovementof the water,to changesin water pressureand other disturbancesin the water.It
consistsof a seriesof interconnectedlateralline canals.One long lateralline canalruns the lengthof the
body on eitherside along the lateral surface.This can be readily observedas a thin light-coloredline upon
the skin. Othercanalsare found in the headregion,nearthe eyesandjaws. The canalsopento the outside
of the skin by tiny poreswhich admit water.
Examinethe body wall along the lateral surfaceof the body to detectthe lateralline canal.Use a hand lens
to find someof the poresalong the lateralline on the surfaceof the skin.
Tag the lateralline on an externalportion of your fish. Tag the lateralline canal on a muscularportion of
the body.
Completed
AMPULLAE OF LORENZINI
Thesesenseorgansare modificationsof the lateralline system,and are similarly innervated.They detect
changesin water temperature,electric current,and salinity.
Examinethe undersideof the snout.Note many largepores.Pressdown upon theseareasand observethe
gelatinoussecretionexuded.The poresconnectto elongated,cylindrical, tube-like canalswhich storethe
jellylike secretion.At their basesthey form the main bulb-like ampullaeof Lorenzini.
Removethe skin from the undersideof the snoutand observethe structuresiust described.Tas the
ampullaeon undersideof the piece of skin you removed.
Completed
THE SKELETAL SYSTEM
The internalendoskeletonof vertebratesprovidessupportand protectionfor the softerbody parts.It is the
fundamentalsystemupon which the body is built. A paleontologistcan reconstructan entireorganism
from a studyof its bonesalone.
The most striking featureof the shark'sskeletonis its being madeentirely of cartilage.It thus exhibitsa
"fetal" characteristicin remaining cartilaginous during the animal's entire life. Although one may find
q0
someareasof ossificationdue to depositsof calcium salts,they do not form the "bones" characteristicof
the higher vertebrates.
The diagrambelow shouldbe labeledas you read abouteachpart ofthe skeleton. For convenience,each
of the labels(you're responsiblefor) hasbeenunderlinedin the discussion.
1i
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THE AXIAL SKELETON
In vertebrates,
this portion of the skeletonconsistsof the skull, the vertebralcolumn, and the rib cage.
The Skull-Chondrocranium
Two regions of the skull or chondrocranium are identified, the neurocranium and the splanchnocranium.
Learn to locateand identify the parts listed below.
Rostrum - The most anterior portion is known as the rostrum. It is medially located, taperedanteriorly
almostto a point, resemblinga bird's beak.It is the supportfor the shark'ssnout.Dorsally it is hollowedout and trough-shapedwhich in life is filled with a gelatinoussubstance.Ventrally it is keel-shaped,with
the keel extendingfrom about one-halfits lengthposteriorly.
Nasal Capsules- Two large spheresproject laterally at the rear of the rostrum. The arethe nasalcapsules.
Their walls are very thin and thereforeoften destroyedin the preparationof the skeleton. In the diagrams
they are completeand you may seetheir externalopenings,the nares,ventrally.
VisceralArches- There are sevenvisceralarchesthat supportthe mouth and partsof the gills.
MandibularArch -The hrst visceralarch,the mandibulararch,is modified to form the Upper and lower
jaws. The upperjaw and lower jaw are lined with severalrows of sharp, pointed,triangularteeth,
modified dermaldenticles,that are locatedat the edgesof thejaw. The back rows serveas replacement
teethwhen the anterioronesare lost or worn out.
The Gill Arches- The last five visceralarches,numbers3 to 7, are known as the gill archesbecausethey
supportthe gill elements.They are "U"-shaped,with multi-jointed elements.
The VertebralColumn and Ribs - You are to do your own dissectionof the vertebralbones. The tail
shouldbe cut in cross-sectionby the companythat did the preserving. Make a secondcross-sectional
cut
of the tail betweenthe seconddorsalfin and the caudalfin so that you remove approximately5 cm of the
tail sectionof the fish (including the vertebralcolumn).
Also removea 5 cm sectionof vertebralcolumnjust posteriorto the first dorsalfrn. Removethe skin and
musclesto exposethe vertebralbonesof BOTH sections.
Completed
Centrum
lJemal arch
Hemal canal
Hemal sPine
Caudal vertebrae'
9a
THE APPENDICULAR SKELETON
The appendicularskeletonrefersto the cartilagesof the pectoraland pelvic girdles and to their respective
fins.
coracoid bar
PECTORALGIRDLE A"U"-shaped
structurewhich encirclesthe ventral side
of the trunk.
PECTORAL FINS - They consistof three
basalfin cartilages.Thesearticulate
distally with many slenderradial
cartilages.The most distal portions of the
pectoralfins are broad.yet thin and
flexible to allow for free movement.
scapularprocess
cartilage
suprascaPular
Removethe remainingskin and muscle
from one of the pectoral fins (ventral and
dorsalsides). Your fin should look like
the diagram on the right.
basalfin cartilages
propteryEium
mesopterySlum
radial cartilages
metapteryBlum
ceratotrichia
Completed
Pelvic Girdle and Pelvic Fins
PELVIC GIRDLE - The pelvic girdle of
the dogfish sharkis composedof a single
transverserod of cartilagelocatedin the
ventral abdominalwall iust anteriorto the cloaca.
PELVIC FINS - The basalcartilagesof the pelvic fins consistof two elements.As in the pectoralfins,
thereare a seriesof radial cartilageswhich articulatewith the basalcartilages.The most distal portionsof
the fins are known as ceratotrichia.In male sharksa highly modified radial cartilageforms the clasper,by
which spennare transferredto the cloacaof the female.
Dorsal and CaudalFins
DORSAL FINS - The dorsalfins, one anteriorand the other more posterior,althoughnot a part of the
appendicularskeleton,are here describedbecausethey are similar in structureto the pectoraland pelvic
fins. The largerbasalcartilagesare next to the vertebralcolumn, the smallerradial cartilagesare more
distal.Finally, the thin parallel most distal rays are the ceratotrichia.A sharppointed spineprojects
dorsallyfrom the anteriorend of eachdorsalfin.
CAUDAL FIN - One may also find ceratotrichia on the caudal fin. The end of the vertebral column turns
upward into the dorsal part of the caudal fin.
Your final color diagramsfollow on the next two pages. Completeeach. When done,it is recommended
that you GO BACK and check your work (pageby page) for the entire lab. Go through the packet with
your partner,then go through it with someoneoutside your group. Follow the instructions on submitting
your work and disposingof your specimen. Greatjob! You madeit through the shark!
qs
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