1. Analysis of Morphological Variability within and Among Species
Lab Report Rewrite
Ichthyology, EFB 486
SUNY College of Environmental Science and Forestry
Connorlynn Gaffney
February 26, 2014

2. Abstract
Animal speciesare dividedbasedon differencesandsimilarities.Some speciesare relatedmore
closelythanothersandrequire small detailstodistinguishthe differences.Asagroupof four,we
measured120 differentspecimensforstandardbodylength,eye diameter,andthe anal finrays or
spines.We attemptedtodistinguishthe difference between twosetsof similarspecies:the Centrachids;
rock bass (Ambloplitesrupestris) and pumpkinseedsunfish(Lepomisgibbosus), andthe Salmonines;
rainbowtrout(Onchohynchusmykiss),andcoho salmon(Onchohynchuskisutch).Comparingthe
morphometricandmeristiccharacteristicsaslookedforevidence of allometricvariations. We
discoveredthatthe mostaccurate representationof aspeciesinvolvesthe anal fin,where asthe
standardbodylengthis one of the leastaccurate formsof measurementbetweenspecies.
Introduction
All livingthingscanbe separatedintospeciesbasedonaset of generalizedrulesaboutthe
individuals. Thislabusesthe phenticspeciesconceptwhichassignsspeciesbased oncountable or
measureable characteristics.Thisspeciesconceptalsotakesallometryintoaccount whenseparating
species. Thislabattemptstouse morphometriccharacteristicssuchasstandard bodylength,andthe
meristiccharacteristicof anal finraysto distinguishthe differencebetweentwoclosely relatedspecies
pairs. Due to the variationamongstindividualsof aspeciesitcan be hypothesizedthatthe meristic
characteristicwill be more reliable todistinguishthe difference betweenspeciesthanthe morphometric
characteristics.Thislabalsoattemptstolookfor allometricvariationamongst speciesanddetermine if
those measurementsare validarguments todistinguishdifferentspecies.Itcouldbe hypothesizedthat
some specieshave the same ratioof eye size tobodylengthregardlessof the actual size of the fish.
Methods
The class splitintogroupsto measure variousmorphologicaltraitsinfourdifferentspeciesof
fishfromtwodifferentfamilies;rockbass(Ambloplitesrupestris), pumpkinseedsunfish(Lepomis
gibbosus),rainbowtrout(Oncorhynchusmykiss ),andcohosalmon(Onchohynchuskisutch).The first
twoare centrarchidsfromcentral NewYork,and the secondtwoare non-native tothe Greatlakes
watershedthathave adaptedovertime.
My labpartnerand I combinedwithanotherpairof labpartnersto getthrough120 different
fishspecimens.The fishwere dividedbyspecies,andeachspecieswasseparatedinjarsbasedontheir
general size.We measuredtenindividualsfromeachjar,or thirtyof each species.Inordertoproceed
withthe mostefficiencywe dividedthe tasksbetweenthe membersof ourgroup.
In the centarchidspecies,the rockbassandpumpkinseed,we were responsible formeasuring
standardlength,eye diameter,andcountingthe anal spines,butnotthe branchedrays.The branched
rays are segmented.Inordertoidentifythe difference,we were instructedtocountfromthe base of
the finrather thanthe tipwhere the branchingoccurs.

3. The salmonine species,rainbowtroutandcohosalmon,were alsomeasuredforstandard
length,eye size,andanal finrayswere counted.These speciesdonothave branchedrays,soall rays
were counted.
To measure the standardlengthwe usedarulerto measure fromthe headto the hypural plate,
rightbefore the tail fin.Thiswasan accurate measure of lengthbecause the tail oneachindividual could
have beenalteredfromanaccidentor sittinginthe alcohol forsuchan extendedperiod.
The eye size wasone of the mostdifficultthingstomeasure due tothe variationinsizes.We
useda verniercaliperonthe inside of the eye sockettofindthe true size withouthavingtoworryabout
inaccuraciesdue toeye shrinking.
In orderto analyze the dataI createdvarious graphs inexcel,andperformed a2-tailedt-test
comparingthe salmonine anal finraysandthe centrarchidanal spines.The graphscreatedinclude the
relative eye sizeof the centrarchidsandthe relative eye size of the salmoines.The treadlinesare a
comparisonof the bodysize and eye diameterineachindividual.There are also twographsincluded
whichdemonstrate the standardbodylengthandnumberof spines/rays.
Results
Salmonines
The degreesof freedomwere 41,and resultsof the t-testwere calculatedtobe significant(t
stat=-38.16). The P value,whichisacomparisonof the t-critical and t-stat, waslessthan0.001 witha
value of 1.17 x 10-33
.
The relative eye size of the salomine speciesisdisplayedonthe figure below.Italsodisplaysthe
slope,andR2
valuesonthe treadline.The topvalues (y=3.1809 + 18.054) representthe cohosalmon,
and the bottomline (y=0.7052x + 69.721) representthe rainbow trout.
y = 0.7052x + 69.721
R² = 0.0112
y = 3.1809x + 18.054
R² = 0.398
0
50
100
150
200
250
0 10 20 30 40
StandardBodyLength(cm)
Eye Diameter (cm)
Relative Eye Size Salmonine Species
Figure 1. Thisgraph displaysthe relativeeye sizeof the two salmonine species.The rainbow troutis
representedbythe diamonds,andthe cohosalmonare representedbythe squares.

4. The secondgraph (Figure 2) below representsthe comparisonof anal finraysinthe salonine
species. The toptreadline (y=-0.0003x + 14.96) representsthe cohosalmon,andthe bottomtreadline
(y= 0.0007x + 11.88) representsthe rainbow trout.
Centrarchid
The degreesof freedomwere 29, and resultsof the t-testwere calculatedtobe significant(t
stat= 35. 72). The P value,whichisacomparisonof the t-critical andt-stat,wasless than0.001 witha
value of 1.58 x 10-25
.
The relative eye size of the centrarchid species isdisplayedonFigure 3below.Italsodisplays
the slope,andR2
valuesonthe treadline.The topvalue (y=-0.0013 + 0.2827) representthe rockbass,
and the bottomline (y=-0.0002x + 0.1148) representthe pumpkinseed.
y = 0.0007x + 11.875
R² = 0.027
y = -0.0003x + 14.958
R² = 0.0037
0
2
4
6
8
10
12
14
16
0 50 100 150 200 250
TotalRays
Standard Body Length (cm)
Salmonine Rays
Figure 2. Thisgraph representsthe numberof anal finraysincomparisonto the standardbodylength.The
squares representcoho salmon,andthe diamondsrepresentrainbow trout.
y = -0.0013x + 0.2827
R² = 0.7876
y = -0.0002x + 0.1148
R² = 0.3111
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 50 100 150 200
RelativeEyeSize
Standard Length (cm)
Centrarchid Relative Eye Size
Figure 3. Thisgraph displaysthe relativeeye sizeof the two centrarchid species.The rockbassare
representedbythe diamonds,andthe pumpkinseedsare representedbythe squares.

5. The fourthgraph (Figure 4) below representsthe comparisonof anal spines inthe centrarchid
species. The toptreadline (y=0.0018x + 5.80) representsthe rockbass,and the bottomtreadline (y=2E-
16x+3) representsthe pumpkinseed.
Discussion
In all the speciesstudieditcanbe statedthatthere is evidencetosupportthe hypothesisthat
the meristiccharacteristicwill be more reliabletodistinguishthe difference betweenspeciesthanthe
morphometriccharacteristics. Figure 1and figure 3 representthe relative eyesize of the individuals.
Due to the treadlinescrossingandamountof scatterat the lowerendof the graphs,there are not
significantenoughdifferencestouse relative eyesize asatrait intellingtwospeciesapart.
Figures2 and 4 showthe relationshipbetween the anal spines/raysandthe size of fish.Ineach
graph there isa distinctdifference betweenthe twospeciesrepresentedoneachgraph.The treadlines
are separatedenoughthatevenif there wasmore dataincluded,theywouldnotcross.Inthe case of
the fewoutliers,they are close enoughtothe treadline thatthere isnochance of confusionwiththe
otherdata on the graph.
Figures1 and 3 also refute the hypothesis thatsome specieshave the same ratioof eye size to
bodylengthregardlessof the actual size of the fish. Itcouldbe statedthat individualsof the salmonine
speciesbetween10-20cmhave distinctratiosof eye diameterandstandardbodylength,butthere is
not enoughdatato determine if the resultissignificantornot.It couldalso be statedthat rockbass
individuals smallerthan50cm have a distinctrelative eyesize whichcouldbe usedtoidentifyspecies
differences,althoughinordertohave significantresultsitwouldbe necessarytointentionallyinclude
specimensof pumpkinseedswhichmeasuretolessthan50cm long.
y = 0.0018x + 5.7936
R² = 0.0408
y = 2E-16x + 3
R² = #N/A
0
1
2
3
4
5
6
7
8
0 50 100 150 200
NumberofAnalSpines
Standard Body Length (cm)
Centrachids
Figure 4. Thisgraph representsthe numberof anal spinesincomparisontothe standardbody lengthof
the centrarchidspecies. The diamondsrepresentthe rockbass,and the squaresrepresent the
pumpkinseed.

6. These differencesbetweenspecies have mostlikelybeenmaintaineddue tothe inabilityof
speciestomate withotherspecies.Itcouldalsotake the lackof variationbetweenindividualsof the
same speciesinto account.Natural selectionchoosesindividualstosurvive basedonsuperiortraits,in
the eventof an individualmutatingtohave adifferenttrait,unlessitcontributestothe individuals
survival,the traitwill die outwiththatindividual.
The varioustraits amongspeciesare bestusedtoidentifyspecieswhentechnologytoanalyze
DNA is unavailable,suchaswhenconductingfieldwork.Understandingthe differencesamongsimilar
speciesisimperative forquickidentificationinsituationswhichrequire workwithspecimens.