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.

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