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Mating Behavior of
Caribbean Reef Squid, Sepioteuthis sepioidea
Jamie Morris June 6, 2010
Dominica2010Dr.HeymanDr.Lacher
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Abstract:
Sepioteuthissepioidea,CaribbeanReefSquid,usechromatophoresand
iridiphorestochangetheircolorandpatterns.Thesechangesareusedaspartofa
complexcommunicationsystem.Thecomplexityofthismatingsystemhasbeen
mentionedinpreviousstudiesbutrarelyexplainedinmoredetail.Thispaper
attemptstoidentifyanddescribethecolorandpatternchangesseenineveryday
behavior,butmostimportantlyfocusesondescribingthecomplexcourting
behaviorandmale‐malecompetition.
Introduction
ThefocusofmystudywasSepioteuthissepioidea,CaribbeanReefSquid.Reef
squidareafavoriteamongsnorkelersandscubadiversbecausetheyarecommonly
foundamongshallowreefsandcandisplayavarietyorcolorsandpatternsthatcan
changeinlessthanasecond(Byrneetal.2003).Notonlyarethesecolorand
patternchangesfascinatingtoobserve,butalsotheyplayagreatrolein
reproductivebehavior.Reefsquidhaveaveryshortlifespanofabout1to2years,
andthemajorityoftheirmaturelivesarespentcompetingtomaximizetheir
reproductivesuccess(Hanlonetal.2002).Sincereefsquidaresemelparous;thatis,
theydieafterreproducing,theyarenotmonogamous.Malescanfertilizemany
femalesintheshorttimebeforetheydie,whilefemaleslaytheireggsanddie
immediatelyafter(MarineBio2008).Becauseofthedifficultyofstudyingreefsquid
bydirectunderwaterobservation,thereisnotmuchinformationontheircomplex
matingsystems.PreviousstudiesbyMoynihanandRodaniche(1982)and
Moynihan(1985)(ascitedbyHanlonetal.2002)offerbasicdescriptionsofthe
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complexityofthematingsystemforS.sepioidea,butlittlesubsequentinformation
hasbeenpublished.Sincethesestudiesareabout25yearsold,Iwasinterestedto
seeifmyobservationsareconsistentwiththeseearlydescriptionsandifIcan
describeinmoredetailthecomponentsofthematingsystem.
MaterialsandMethods
Studyorganism
Reefsquidareamemberofthe10‐armcephalopodsandcanbeidentifiedby
theirtorpedoshapeandfinsthatspanalmosttheentirelengthoftheirbody.Allten
oftheirarmsareattachedtothehead,witheightshortarmsclosetothemouthand
twolargetentaclesforcapturingprey(MarineBio2008).Thecolorationand
patternchangeisduetopigmentedorganscalledchromatophoresandreflecting
cellscallediridiphores.Thechromatophorescellsareinthedermallayeroftheskin
anddisplayreds,yellows,brownandblackandupclosearesmallpatchesanddots.
Theiridiphoresproducethegreenandbluecolorations(Figure1)(MarineBiological
Laboratory2008).Thesecellsallowthesquidtocommunicateonemessagetothe
squidtotheirright,whiledisplayingacompletelydifferentmessagetothesquidto
theirleft(Byrneetal.2003).Reefsquidarecommonlyfoundinsmallschoolsof
about4‐30individualsandrangefromabout8‐20cminlength(MarineBio2008).
Studyarea
TheCaribbeanSeaisatropicalsealocatedadjacenttotheAtlanticOceanat
9‐22°Nand89‐60°W.TheCaribbeanSeaishometomanycoralreefs,whichallow
forgreatecologicaldiversity.DominicaispartoftheLesserAntillesbetweenthe
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islandsofMartiniqueandGuadeloupe,andhelpsmakeuptheeasternboundaryof
theCaribbeanSea.This“natureisland”,hascoralreefssurroundingitmakingita
greatplacetodomystudy.Itookdataattwodifferentlocations,ChampagneBay
andScott’shead.BothlocationsarelocatedatthesouthwesternendofDominica
andareseparatedbyapproximately4.9km(Figure2).
StudyMaterials
TodomyobservationalstudyIusedsnorkelinggearconsistingofamask,
snorkel,fins,andawetsuit.Ialsotookstillphotosandvideoofthereefsquidwith
anOlympusStylistTough8010camera.
Figure1:FemaleCaribbeanreefsquidinbasicbrowncolorphaseshowingthedifferencebetweenchromatophoreandiridiphorecoloration.PhotographbyJamieMorris
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Figure2:ThismapshowsthesouthwesternendofDominica,pointingoutthetwo
areas,ChampagneBayandScott’sHead,weremyobservationstookplace.Mapby
KinnieEijsink
Results
Reefsquidcanbefoundinabasicpale,basicintermediate,andbasicbrown
colorationinthewild.Thebasicbrownphaseistheonlyphasewhereitispossible
todifferentiatebetweensexes(Figure3).Thefemaleshaveagradualtransition
frombrowntopale,whilethemalesaresolidbrownwithdistinctfindots.Basic
paleisseenoftenatdawnorwhenapredatorswimsby(Figure4).Thiscoloration
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consistsofapalebackground,withreflectivegreenontheeyebrowsandmantle
midline.Thebasicintermediateisthein‐betweenstageofpaleandbasicbrown
(Byrneetal.2003).
A)
B)
Figure3:A)AfemaleCaribbeanreefsquidinthebasicbrownphaseB)AmaleinthebasicbrownphasePhotographbyJamieMorris
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A)
B)
Figure4:AandB)Caribbeanreefsquidintheirbasicpalephaseofcoloration.Photographsby:JamieMorrisandDr.Heyman
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Reefsquidspendthemajorityofthedaycasuallyswimminginshoals
(groups)andchangingtheircolorperiodicallyforcamouflagepurposes.Theadult
reefsquidchangedtopaleorwouldblendinwiththeirenvironment,whilethe
juvenilereefsquiddisplayaplaidpatterntohidethemselves(Figure5).Theshoals
Iobservedwereverysmall,only2‐4squidpershoal.Interestingly,Iobservedthe
squidswimmingwithonlytheirownsexwhennotcourtingeachother.
CourtshipbehaviorwasobservedatChampagneBayon5/30/2010from
about2:15PM‐2:25PM.Courtshipbetweenmalesandfemalesinvolvedaslow
parallelswimmingtypeofdancebetweenamaleandfemalesquidwithsome
interruptionbycompetingmales.Theprimarymaleflickeredbrightlyusuallyon
thesidefacingawayfromthefemale,whilethesidetowardthefemaleshoweda
stripedisplay(Figure6aand6b).Themaleperiodicallyexhibitedafullbodyflicker.
Thefemaleoccasionally“answered”backwithapartialsaddledisplay(herbottom
Figure5:JuvenileCaribbeanreefsquidshowingtypicalplaidcolorationdisplay.Photographby:ArielSklar
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endturnedlighterleavingtherestofthemantledark)(Figure7).Thecourtship
dancelastedabout1.5minutesbeforeanothermalecompetingforthefemale
interruptedthecourtshipbehavior.Themale‐malecompetitionquicklyheatedup
withdynamiczebradisplaysfrombothmales.Themalesroseupcompletely
verticalinthewatercolumntochallengeeachother(Figure8).Tointensifytheir
displaysthemalesspreadtheirtentaclesandspreadtheirfinsaroundthemantleto
makethemselveslooklarger(Figure9).
A)
Figure6:A)Amalereefsquidisshownhoveringoverandtotheleftofafemaleand
heisshowingapartialstripedisplayandapartialflicker.
B)Amaleshowsaclearflickeronthesideofhisbodythatisawayfromthefemale.
StillshotfromavideobyArielSklar
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B)
Figure7:Amalesquidshowsafullbodyflicker,whilethefemale(below)responds
withasaddledisplay.StillshotextractedfromvideobyArielSklar
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Figure9:Themaleexhibitselaboratezebrapatternaspartofanintensedisplayof
male‐malecompetition.Thespreadingoftheirtentaclesintensifiesthedisplay.Still
shotfromavideobyDr.Heyman
Discussion:
Figure8:Twomalesquidareswimverticallyinanelaboratedisplayofmale‐malecompetition.Notealsothespreadoftheirtentaclestointensifythedisplay.StillshotfromavideobyDr.Heyman
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Myobservationsofthereefsquidcourtshipandnon‐courtshipdisplays
followverycloselytothoseofBurkeetal.(2003).Thoseauthorsdescribedwellthe
differentdisplaysseenduringcourtshipand,male‐malecompetition.Whiletaking
videoitwashardtotellifwhatwewereseeingwascourtshipbehaviorormale‐
malecompetition.ItwasnotuntilIwatchedthevideoseveraltimesthatIfound
thatthevideowehadcapturedwasindeedmostlymale‐malecompetition.The
Marinebio.orgwebsitestatedthattherecouldbecompetitionbetween“2‐5other
males”forthefemale,buttheintensityofthecompetitionwasnotclear.Themale‐
malecompetitionthatIobservedwasabouttwofullminutesofnon‐stopdisplays
andcompetition.
Throughdirectobservation,Iwasabletonotonlyseethedynamicdisplays
thataccompanycourtshipbehaviorbutalsothelengthoftimeandeffortspenton
eachcomponentofthematingsystem.Theactualactofmatingissoquickthat“if
youblinkyoumissedit”butwiththetimespentcourtingandcompeting,itiseasyto
seehowtheyspendthemajorityoftheirshortlivestryingtomaximizetheir
reproductivesuccess(McKay2008;Hanlonetal.2002).
IfIweretodothisprojectagain,Iwouldhaveamuchbetterideaofwhatthe
male‐malecompetitionversesthecourtshipbehavior,sothatIwouldknowwhatI
wasfilming.Becauseofthislackofknowledge,Ididnotknowtostayandkeep
recordingtohopefullycatchthematingofthesquid.Also,becausesquidtendto
comebacktothesamematingarea,IwouldplantoreturntotheChampagneBayat
about15.24°Nand‐61.38°Wwherethecourtshiptookplaceinsteadofchanging
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locations.Extrapracticewithanunderwatercamerawouldalsobebeneficialto
captureclearervideoofthecourtshipprocess.
Acknowledgments:
MostimportantlyIwouldliketothankDr.HeymanandDr.Lacherfortheir
helpandsuggestionsformyproject.IwouldalsoliketothankDr.HeymanandAriel
SklarforhelpingmecapturethevideoIneededtomakethisprojectpossible.
ThankyouKinnieEijsinkforprovidingmewiththemapofDominca.Ialsothank
theSoufriereandScott’sHeadMarineReserveandtheDepartmentofForestry,
ParksandWildlifeofDominicaforallowingmeaccesstoChampagneBayandScott’s
Headtodomyresearch.AndfinallytheArchboldTropicalResearchandEducation
Centerforlettingmestayhereandusetheirfacilities,andfortheirhospitality.
References:
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MarineBio.2008.Sepioteuthissepioidea,ReefSquid.
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