Integration of the Electrosense with Other : Implications for Communication

Stefan Schuster

Illstitut fiit Z..l.:tie U, Ll !1td.sität E rr.üt Niihl struLttrtL c..-i e,,,,ii;',,,ä,,,i,Äi;,:i:;l;;,ii,;:l:i::;:,"i',:;:b''3' s' D elt)s' L r'!dt

ABSTRACT

The outstnndinA ctecbonoro. and elc.trosetrsoN,biliries ,seücdt, oI.lecbi. tish enablc thcn to exchanSe nNüges n,". u.t.n,n"t rt,.,ti, r,_ ..., ,,,.r inn.."ss,Lrr€ r. most oth., animals. llut ",.]j ' 1 .,1 rr.a:.ö\.1..,\ .rd..F.r,.m olerr., ""'': r,h p",r , rr!r LF\.u'1,.".,.,'. ..,,: ..,f,b",,;". ,:'1":.:- \rstrinI,: s rurcri.nrtän!l ., i,,i''' Dr.b.rtrh."','., rr ""ll"iii"i i1,..' " 1",i _i-, 1","f ä, J. l. . ,.,, i,il;l i": t-, inrr.(.ur,Jr., I .Lt, i..,*.h.o.rI L,t,; p,*F'., ,.r,.,n" ,n,-.,1.. i,1. ,,"r ,,8,," . ._ a-.i.,-,;",; el€.tric tsn conl.l r",: ,.";; ..;g*Lren.tit fron uritizins morc dran.n o-,.. ,ig,'r.. -po.r.,;;; ä",fi11: prnicrl..llcnd ;,: ä;:*ä ;lj.",:l;l'::':l::J:: ;:,: orsisn.ts s€nr snnuttan.ous\, icrcss se,crar a..*r.. rÄ" rdnrblr nt p.+ *-,rJ U...iir." ble hb,ia!!. rr"o,. r,"l *nna ,n, Pr . "o de r' ll i'l\P'rf i' hc'e r Jr'..',\ ToJ,t ro,.r.t.n,h. J"r..r b or mu,.*n. "'-"""""v'ommrnicarion svst'ms ivitrin a *"rr a+i,,., "*.*,r,i,r.gi.ir;;:;k. K€yho'd\:\lt,r',r,.'..rt.oi ,,.V.i,r, sN, H...,.r t,rrd,.,1 .,,,,.,tr,r,,-.rLi-.r.,: ',' Ir'tr1 t'- kr tßh 782 Comn nicntion in

photoreceptor bundl( 1.. INTRODUCTION al. (1997)suggestihai between 520 and 540 eleÜromolor l^ hv -tu.lv hcanr!. and \ ii'rn in ele' rr:( lr'h s I o-e absorbs long waveler "ulstJndrnB ' o\ e- ,""'"i", ii'-."-..i,t,'rr' ie' , n.role thLm to e\( h rnßc mes'ag+ +' erl\ and co-workers now clo:er loJl rt lhe c' nsh arnF as .haffcl rrr.,.. es'ible l. m,*l olher 'in;m?l'l A device to collect mr " r".,*.'.trricatrinsh"h-rhdt(le' tri' rr-h Pro\iJeinrere'rin8 about 600 rods, 25 rhJl '-r.'"i.',i.iil,'," h"w .rn:m rl' c'rn beierit r-om Jrrrr/inq mor( anangement (Ulbrich ."f "'pr,-F eh'l :c{i'hdo on,.!eri-err ä lrne. fir\l ., nrr.rry to'omLUlder'r*umPrions is not optimized for ci lhe'n logelher trr|r otl,er b(ll tun,lr(,n:ng.Fnsor) .\"lem. rr d rr-e presently do not unde ",^-e* (omm h :rh ü"' i".i'. s".""J ,r,.^ limirä r'or ' rn rni'ärrns in oul understandint """..' "* 'ri"l' h) .,PProrri.'rFr\ .'g".r. rhur ,he ri-h 'mendrrrg "i"lt,'..i".i'.".'i.r' $;rlr :r' orher 'en'ur) rb:lrt:c' I wilr ärcue thar TeyssädreandM( ,'n,1..'tantlne,het,v'rrwhthPlecirkfr'hu"car:nteractionol'l'errtänouc'.",'." see by using the ' ;;:;.,:'; i.:i",..;;bitirrer in 'pc.'rrccomn'uni'dtrol rer(vJIrr ra-r '(ourd an indicator. This stu{ ;",;;::;'-h,; ,." LJ'.g u. ra t" 'ruot murti"en'ort intesrdtrnn rn a $err 1x), the fish no longe ..,?."i',r.r, ,r ;on,,\t crrrririS uP rnrere-I in c''mmen'irg uPon were Luüble to percr "",-"Jrh- encle;r nr r:- the"" n'J:n pL'posc or s rihnB lhi' chJP'er 5e\ eral .rPn+s siripes. Moller et a]. ( gererdted br'ad t,, f,n. "f rhe nortr^l-

phororccepl^r bundle{\.4.twä,r.io18)dncJmd)rrdcji,ntiBtrtvi.ir,.,C;är er al. (1.)q7l ,uBtse-r 1t.,,, bp" de" I p,,rph1 rop.in p.gmenr r.U_oiL,inq," auetenein, b, rhcen 5ZU .rnd 540 nm). dl t,.J.r onF ,,,1her \ ijudt pigm"rr L pre,errin.rL :b,:rb. long w,rr,,cnrrh- ,b.\.e b00 nm. A dera ,eJ .iud1 br li".*"u";h dn.r , o ( orler\ now reve,.,s rhnt lhF morm) nJ r.trra i. fai more rh.rn rLr,L a de\ rce ro colhLr.. mu, h tighr d. po.-ibte fa.,rph,,toreceprorL,unJb.;;;,.: dbuul 600 rod-. ,,ls.one".rnd rt MLi.ter ce,t. in a triqhtl ,randrr,ji,,eJ dl'dnßpre t/U'bri, h,etrt.,20L, rj Rer, h(rb..t .p",...on],ntriur,_um.i_u-eir. r- nut ont ri,/eo ror..rh hir.B photons bui rathe;..,."ln_,,,."rr Pre.erll) don^, Lr,rd, htdnd. ßecon-ingyen..t\ Itdetini,ct\ D^,vrcte"urDn\.\".,,;;.;";: m ^Lrr Jrder.,.'nJirB ot the -trü,h c.rnd rL.n,ri,u or rr.e mo.-u.in ",.,,,r änd Moller .Teyssidre 0 982) demonsh.ai€d that Crdrroxcr,rs could äcrua y -eF b\ ucins th. fjsh . opr.r.otor fotjos i 8 rc_por{e to a mov rg Brätirg a. dn indrcdror Thi. -rud) .rt5.,.howcd tt-.ä, .rr h I er tighr .n,cn iti(, (;bov&0 l\). lhe h,,qe..hor"ed l;.h no op,,,mor,,r rc.oon.e: rndic.rrinB ih.r the ri,h were Jndlrie to pL-ce,\c th- conlrJ_r br t{cel ihc mo\ing bt.;t rnd ahrre siripes. Moller et (1982) al. were the firsr to demonstrate th"at vistun ptays an important roi€ in communjcation in clectrjc fish, acft1s tosetiler;ith cle,lr,,commun,c.,uon In o,oer r,, resutrrF s.oLrn.oh".;n r?-.,r,..ii"" |l.\ enrlc-. 1'ri--lUd\m.rdeitpt.ru.ibtprh. he_u,,inrrrerrirr,doublebandini ,lL, p,/, iip'.r!. rol,..r..r , rsudt .rgnrt n-o,idt.,.mmüqiLdrio,,.Vr5ion; al.olil,l\ loc,,lltrrL'utF ,,l et.,rdpirtssucce_s.fCrn,r,,,,ar,,:rrorderfrnde drro brccrmd'r',. tuq6t dr.,J hd. r. entl) be,n ,h^h n to hslp thc fi_h n ,rtntdinrnp Pm\imi'\ l^.helrcr, rM,,||er 2002. R,,rd.,\nJ \,4,, er. )002/. De.pitF ir: lol\ re5.t\ rnd power C,trtlnrt, ttt. (rn Ji.c"im,ndle !irual pattems (Schusterand paftern Amtsfetd,2002)_ recognition is, however,limfted to very low ambienr lighr levels ofabolrr 10Ix. A lcainect abilitv to

Jncl HerlLrl.p e, oo'.Ror ,rr\er Jnd DLL loo-r A.- rd:ntl\'C1't11tr"-ttt' Information abolrt the strip \.'rl.i .l.rc ,r -r. pJrol oi lhe retr.,rclFJ frtsure "'.roPir'ni frofl lhP f''^d by analyzing i,is äl motion !,antage poirli. Wh;n it viewc.l two other paiterns from this vantage ponrL it distarces and fixed orienia snaPshot staiionary pattern, but th€ üoül.t clioose thatone that Provided the best match with the sbred while the fish (or its Tocriticall), assess thisnotiorl, tests werc Performed in which rescalec:t velsions cyes)l was such that What about thc visu of the t(rc;riginal training Paitems were shown The rescahrg t'",h.err r,;ri'rn- rorrld fir .qu.rlli (ellr(lLr.rlr\{'lPmP.rre lr P'rtF l pioneering workon theopti lisuauy ..r.'rO.r'r, * irrr tn. hyporhc'i- tlrc f''lr l"rlcd lo d'\ r in'in rte rlrF two rc-cnled and electrically ev( ü-,r-ertb(!,rtrot-,,,,:art...aro-,.1u"..dilu.rl.r-hi-rotbLa.,,.\Flne\.u"l electric fish, ihe black ghos I know ..,ronr w-. -ur"ol< r.'r'-ol\c rl)e drf/, rcn.e bL ween lhP rwo rL*r'rled i'lu-es of no rcportindicaii ihese and similar experiments suggest ihat G,]iltlo'rc,rrrrs üses temPlai€ ii has a conspicuous whii€ matching, one of ihe simpLest nlechänisms of Pattern recognition This do not yet know its rcle ir ncchaniim is not viewpoint invarianr the inäge of a given pattem varies discover strong responses Even more drasticall], as ihe chosen viervpointdeviates from tlt one ai ü'hichthe templaie surprising is \das stor;d. Therefore, being able to use such a temPlaternatchnlg sysiem elecirosensory stimulus c jamming requires adaPted bchaviors, which allol' nnportant obiects to be seen from nüllified by a ele( fixed vaniage points. of the tectai cells, the rec€p bee- r€gister. It is int€resting th; r'r te.' t,* i-.'.r. ',rroLrldirB'or arre't 'rd reedinSPldle "nd "'lni ' rlimrrednumber(1 !rehPoilFona signals in these cells. Perhal rä,o- "DrLar'to 5r( r/ \ ies' r,Lrdl a,r.n..l pi'rn.tnrtc renl rel rms rl-e-e n rdlsr"llow rhe 'äme PJrl- detect notiou and allos's ( 'trb'cq be implemented. anci are ihus able to match--at the .orresPonding viewpoinis the actual and Reducint importani visrial th(] siorect rciinal aPPearance of each landmark Presently, we do not knoü' brain area processing horv anel in which iontexis Gntrlld,rctrrrs makes use of its temPlate matching importänt änd I 'l L!i\ rl'c -L -PF. t (" rl l"ndnrrk- as compared to non eleciro ,\ stem. Brr F , lrr. l ri.h ^ :enl- wilh PromrrtL 21102 R,rjr- dnd \'4oller' 2n0)l Wullimann, 1988, Wuilimal 'lre estFgy. re..n. re-Lrlr, ot Morler rM^lle- shon, thaiörrnl]lorrerrrrrs can indeed us(] vision io locate a shelter' Exiending these stuclies would behighly rewarding: Can the fish also Pinpoiniits shelter 2.2 Headng and Soun p .trrrorrndrng Inndmrrl- lhdt n^ Prot ded bv b\ u5ir ri-u.rr 'er"ls,' 'rre All eleciric fish invesiigar€ tlie rrcit rr.elrr ä L..rr,.r '\elre-l'npprns 'cenario'o rld be rm'rBined rn \upP"'' lhel''1ndrl€d headng has not been shdi hhr.|lLn'Dl.rr.nrrl.Lir!,woL,ldhe.,r'*fu 'l',itets) that a good ofhcaring ;'idrng pl*e lc'helrPr hJPPing rh' li-h t"u d rl(rr it. roLrtc hl In . d, lI e.l this is thai ihe South Ameri the roact by orienting so thai the retinal images of find thc nexi sheLter m of the Ostariophysi h whic lnndmarks overlap ü'ith a std€d temPlate of the surrotmdjigs' surroulding wall io the nuer ear. This c rr rrorn n.rr1r.r:lar -hnlier' rl-P rlren b\ rne fi'h r.rl il,i' ' "nr'rlon '"Jmed of specialists (see orpass b"arrrg rhrr rl (ourd Lr'e t' tsrr ro rhe re\r oror'd, i u', ll l mormyrid fish, on the other "',-,ro rhis lheri'l-'ur''d'o\erl'rr8"di'trr ce'e\er'!ih t',o'.8, pto.". R-l'e.,tnB specialization that increäses be clen in rdrrhFr r'rnginS mitsralion' r' lhe 'ie'., u.i ."u'i tsrride'l of iheir itu1er ear a smäll ot '..',.i leedirtB grl.u rd. rMolle'eL .r laTo) rr-h - ro iurn.rl " von Frisch, 1936, 1938, Diesl use recognition to deiect the conspiorous The fish coüld also lisual Pattern both otic gasblädders result of a conspecific' However, the low sPatial acuit)' doubLe banding Pattcrn The f unctional implicät ona ÄÄt"r"1a,2002) ph;es an uPPer limit of aboüt 20 ct1l.on the is.t.'.'"t"' (such as ihe momyrid otic I patlern can be resoh'ed Moreo!er' the fish must ;istänce at ü,hich thc stripe ossicles (in the Ostariophysi with respect to each other' Both woulcl bePossible assume a fixccl orientation is sensitive io particle moti in many known displays of mormyrid fish (see Kramer 1990' Mdlet 1995) ,/1..'rd1i,), r)lllr. f1r',1,.s,rrn' rt, O/ha

lnlo niti(in nlroLrt iht stripr Pittcrn of. c(llsPecific i\1ul(l .lso bc 'rcccssible renro\. the r.sh iction L() br';rn.l\.rirrg vislril nrotion cLrcs, I hich urIlt] 'lose ini, ii drsirncLs ancl ti\.Ll (!icntiliiorls i cloift so, the tish \\1)Lrld not nnaly/c ihe stnt(lrir\ pntlcnr, Lrnt thr \\1r\ irr rhich thc P.ltiern n]o\es o\er its r(tina Nhil. thr iish (or its c\$) nrov.. r that \\hat nborl ihc \i\Lrnl .Lrilit! if SoLrth Anrcri.rrr knif.iish? In his plonr'ü nrg $ ork on lh. oPtic llctunr oft'lcctr i. fish, tl.stian (ltl82, 19iJ', stlrLlitd :alcd iisu.rllrrnclolcctricrl['crokci]rcs]lofsestonlo\ingolric.tsln;rSrlnlrotin)rm isrnl €lectri. iish, thebli.k illnrst ,4J't, ,.,rr)ir/i r/l'rll''rrs l'his lish has smalleves and I knoh ot no report i.Lliclting nn oclrlonx)ior slstenr. Sj ihr lo C'rrrt]lor'(l'Jls, ('.rlLrili('r(), n1r(l .s Nitll C'rrtlr|'r' r/rrs, pl.rtc it lr;rs a conspicLrous \ hite t.iirrn '\'e This do foi vtt kno$ its r(ilt ilr connrlüri.ilion lt mLrsi ha\t been a sLrrpisc n) tliscov.r strong rrspon\es k) visu.rl nli)tion in nrost nrcinl cells of this fishl platc E\rn noro sLLrPrisirlg is lhnt adtling n vislr.ll .oDlPorrent n).1 tnoving elel:hlscrrsory stimulus can conlPlc'tel! rcstore.esPorlses ihat h.ld bcetl nulliiicLl b\ .r jinrning cl('.tr-icnl stimLrlrrs (Bastian, l9E2) [4orco\er ]n nrost ol ihc tt.tal c€lls, thc r.cepti!e fi.lds for \ islril nncl elcctric.tl siinltlll wcrc n registcr. lt is iniercsting th.rt B.sii.n found no resPo.scs to sla t( )nnr)- ! isuai signal\ nr these cells. I'crhilts ihc \ isll.rl svst. fish is sPechliTcd to 'rfelectric paih dctc.t noilon .nrl .rllo\!s onl\ the simPlcst P.tt€rn rccognjLl()n str.ltegics to be ilnplcnlelrirLl. Itcdu.ing ihesc to ihe b.rt c'sse.tials nlight t\Plain wl\v nnportnft !isu.l L.r.rir) nrrns, s ch ns the ! isrr.rl nrca of the di.nccPhalon-an hnrg nnportint p(,.r+irrg .rnd rrlr\ st.rtlon a!c Lrrgclv rcdoced in Grrdtlr''rr'rrrrrs * compa'ed n) non c'h.lroscns(!! tels)sc (L.rznr ri.rl, 1981' \orthcLrtt au'] r002) nulliln.nn, l98S; \\trlllrn..n rrrd North.Lltt, l!lq0) dnrg €ltcr 2.2 Hearing and Sound Comnunication C Lr), in\.stigntod t!) Lldtc hnvc c\eclldrl h.irnrg nbiliiies' Whilc )d in All .lc.tri. ilsh hurnrg hns not Lr.. stLrdLcd in tlie Ynsi Dldi()rit\' of clccitic fish' it is likelv goo.ls..s( oa hcnr ilrg is s i.lcsPre.d.mnrg thcn Orr€ re.s{)n tonssume then ih.tr this is thnt thr solrth ,\mrricnn g\ nl oliflnll cle.tric fish belong t.r ihc gr otlp r)i thc OsLrrioflr\ si in \tlri.h tht Weberi.rl ()ssi.lcs .(nlncct ihc s$'inrbli'1cler hnlltolh! inno trr. lhis c(nrncctiof g$.r.rll) irlnccs these iish irr ihc groLrp oi henring sp(i.tlists (sce H.ü'kins, 19S1, llrpPcr ct n1.,2001) Ihe another^ftican ,!iih lnornrvri.l lish,{,r thc'other hrr1d, hck. nlclrc'ri.rn aPP.lratusLmthire sPc.inli/.rtnnr tl1.rt incrc;rscs tr rqrrencY tange änd s.nsitiYitl T(i each sacculus ni tt,"i' lnn"' crr, n snrall oii. gnsbhddcr is tightl\' .ouPled (HcLrsxrgcl 1E26, yon Fris.h, 1936, l93E; Di.ssclh'rLSt, l9:lS, Stipetic, i939). Rono\ al of g.ts ironr both blrdllcrs rcs lts ir\ llrsscs nr sensitLvitv (Ynn..Ll a Ltrtsingcr, 2000) uit_v oii.gis oi strLr.lur( s cither closc to tlrc inner ear ihe Th( llrn.tionnl lnrfjicrti(lrs s!.h (su.h.rs the nrorfr\rid r)tic brlbltcs) or .orlfeci(t to itLrv a ch.lif of nlo\enlrlL (in cnn b. Lurderslood ns tolloh s:lhe i'n'r c'r itsclf rible ossi(l.s thc'clslnrioltrysi) pdrticle frotnü d€cnvs !ery raPidl) \'ith )95). is s.n'iti\c i() p.rti.l. Dr()tn)n Lrut 746 Co ltlt ticntian hl Fislls

distance from the source, päriicularly at higher frequencies (Harris änd van To daie, not a single Soüti Bcrgeiik, 1962, Kalnrijn, 1988). A compressibl€ struchire, however, responds sound. Amont morm)'rid fist (RiSleY a to ihe far ranging pressure component of a sound waYe and can rhus be sei Gr?dtroncrrrrs Pctcrsi; into pulsating motiol even by a distant source (Morse and Feshbäch, i953). l?dspfllxs (Cr,rs tord et ,rl 19 As an effect ofthis pulsating motion water particles or the ossicles are moved PolLDtl Is tsid i, there is sood back and forth and can now stimulate the inner ear even when ihe sound more massive in the sound-Pr' source is far away and the direct päriicle motion has long declined to tevets the swimbladder into vibratic Itrl q 0uld be urdere.t.rDle ro the ,,nä d(o nner edr. Huan8, 1999) The Nost n1terc Theevidence on hearing abilities of gymnotilorm fish is limited tostudies specilic electrrcäl communical by von Boutteville (1935) who trained the electric eel to detect sound, Ladich posscssrng the most comPle\ (1999) who derived an audiogram for Eigcrrrrflr,, .,i,"scc,?s on the basis of rhe (Crawford, 1993). auditory brainstem response, and Krämer et al. (1987) on GvmnohLs carcpo and HypoporTls sp. ihat elcgantly exploited the so-ca]]ed 'novelty response'of 2.3 these fish. In response to sound onsei these fish acceieraied rheir discharS€ Electric fish do have an intact l rate, thus, enabling the researchers to characterize hearing abil ies wirhout caled superf icial neuromasis s( having to irain the fish. Botll speci€s responded to sound upro 5 kHz, one 1989). Note that äboui 100 süPr Gyrriofrls cven ripto 7 kHz, and had th€ir maxinrum sensitivftv at 500 Hz about 2000 neüromasts in (Aypdpor'rt and i000 Hz (Cyrrlt,s). The strlrcture of the Webeiian ossicles electrorecePtive blind cav€ fish probably varies b'idely among the South Americän gyrmotiform fish and a Given ihat canal neüromästs comparaiive study wolLld, thercfore, be rewarding tocxplore the implicarions supertrciaL neuromasts io lol of these struchrral differences on the fish'shearing äbilities. Suchcomparaiive Coomb5 änd MontgomerY l! studies woü]d largely be simplified by workin8 wiih species rhai exhibit a mechanosensory lateral lin€ novelty response io sound onset. movemcnts arld that the mect In compaisol, the hearing abili ties ofmormydds have atrracted farmore .omD('nised. Tlx! üew fi ts ni nlterest (\,on Frisch 1936, 1938; Diesselhorst 1938, Stipetic 1939; Kramer et al., ..riäu' electnc fish her€ sh 1981; Mccormick and Popper, 198,1; Marvit and Cnwford, 2000, Fletcher and transparent obiecis that could Crawford, 2001). These stlrdies showed that mormyrid fish hear over a wide electrically (Heiligenberg, 197 tcquerr ! rd18.,.,b,'Lrt 100 lo I00n H/' w rh loh lhredrold. re.g. Tqob rF I animals had no Probbm adjr at 500 Hz for Br'torontyrus bn)chllistiits). Detailed reports ärc available on FPa were elecirically deteciable. t struciural and fünctioral aspects of thc otic gas bubble (Heusinger 1825, as from behavioral considerati Stipetic, 1939; Werns and Howland, 1976j Yan and Curtsinger 2000). An over the role of tl€ suPerficia interesiing receni finding (Yan and Curtshger,2000) is ihe presence ofa ihin detect slow_mo!in8 and star septum ihai separätes each otic gas blädder into iwo chambers of differeni Heiligenbeig, 1977, Bastian, 1( sizes- The funciional significanc€ of this is presently not known. A survey of ones to direcily test this inte the inner ear structur€ ämong 18 Iish species indicares intriguing specializarions needed to make general stat€ in normyrids (Poppea 1981). In conträst io ä]i other species, in which two diverse as the'electric fish' I vertically and two horizontalty sensitive groups of saccular hair cells occur, trom pnmary mechdnosenso Gtlt)thotltrtlus has only iwo vertically oriented groups- The auditory nerve as from sccondarY (midbr.in) makes a projection from thesacculus io the rhombencephaion (8e11,1981)and /€pto, ry,,.lrrl5, Bleckmänn Jnd from there to a mesencryhalic nucleus in the torus semicircularis (Häuged6- Some prrmar) aft€rents of E{ Carre6, 1983). Crawford (1993, 1997) reports that many mesencephalic The secondary (midbrain, i (auditory midbrain) units respond in a highly selective manner to temporäl ,4/f erolrdf l]s, were generally ]e chäractefi stics of communication relevant soünds. above 8 cm/s and were sens To clate, not.1 snrgle South Amcrican clechic fish is knoü!1 .o.r . .irr.,..l\.. to produce ,!l A'nor i rr,. r.\ n.t -h...r r * irr (r\.iw-l l" \',,..rtri( L,tn|1.,..1.t,t.. ,. rRr\l,r rt "..r ..r,,\t.r ..r. t- {r / ./,jJr-,..1. , d,, .,n,1 I '. ., r.. r( rdtrhr., , r.) . ./,, i!'v-.,. L, Br.r ,on .|lo ,a89, Ir r.t|.)t..'1..,,i.t-. rt,F,, ,.l:,,.,d..,,d.n,_.t,,,..rJru1rn,, ^rdTL-, g ,,r-.r..",i.I r', mor, md*i,e.n tt,F \,.rr,r_.,r^d,., nB rr.i\ tnJ, rr tne.it"nt .tl..,,.. -..: 'he .h in blJdd. I trrr,,\ .,,,,,.,r\r,."t".d:;l ru"rB Tr.Ju.rnf iquor lf,.n^.i r.rr".rr4,.p,.r,.rr. I rtlr,J,/ rJ,,.r ti.htrirn.e\_ -1,-. I. pl,\lri,. .ri(..r..,r , ^rrf,r b,,rr Ju.,,i,eo n, Dl,brolv rrF 1r,ß1 ,. P_N' '-I i rrl,i,\.r..u-r -r-n.r ,llil ,)_t,.nkn,,qr n:r.r ri,ir

2,3 Lateral Line Electric fish do have än intacr Lrtcrat line cnnaj syslem, bLrt the nlrnber ofso_ rlr r,.,. ..+rr. r,, Lrq r"rs, r\. ;, dr..., .r {\z.,bo. , or, , vr..ih, r. ::i:Jl /8"1. :,'1.'fj.\ol,lr dl. L'.Ut.=ur, ILJU-r.l,e.t,,.rln,.ur!,I-.t,ir e,,rl|r. i.lr.,,rr,r,.t!\ t_ !o!r uu,' F., .,n...r. r r..d. ,h ,t.J/.t,. h.t tu8o/ ... .r^,r_ crp.r,\'i.,rJrrrebiId..\eli.t tn.. 4.r,,.J..f.,1:r.,B.1F.Lit.,trdr,dD,,.,/ot In-rl Lr,tsr It.rt ..,n.rl nprrri,,n.,-tr r.. -1 . r"l r,, ht*,r.r -tin {.pprl, .r, r- ireqr.. . i,.- rrc i.rl r\'u.r1,r.,...o t.,trer,,,,. r, e \4Lnl t-Fr. bt,.t.,r";.-t;,i; (,.a b,.,r.,j qnn,I ,.,Lrrs"rr V,'r. ,.i.rr ,r .,'.. _.nU, ,JEg,,l- t\.rr In,. r'nn,ßei ..r' r', .,,f! Lt, rn,. ,,r ..,-.r,i, ,i.\ r_.1.e. i,, ,,ed io dere,rr".r n."pr. ,t. I,C.l.,, ln..,,r.t.,.|l,.,t,iFt,,tr^n,,J,,{\e ..,."., lI1lrt,i;,. .. r I11,-,'-F,J ttr-\rF,\rir..ri.-tv$rl.r-,,-,\L,Lr.r.,*.,,,,pe . ," .., ,,, fr \d ,.r-, e r i. li-l h-.. .t',h . r,, .o ",",.r u. p ir -r,,,, r irr. re..te, tri. r-tr r-rr-Dor,rrr ol.xrL- ,.,1 th.,t tJ i, L r. nt,.. tF oerF. tc.i n , . t ..nr-al r h,., ,,"r elF.l-r .ll\ /ll.il!FfLr-/. ru l.r. 1t.-r.r.77r.trr,.,.rt..r,r,,,...rt..r...,;i;: - I"l-r..dr,,,tf..,,nri-.r.r,r..r nqr..rt...t. u,.blr, _ .,,Ln'.rrL'i

Lr sr\tlJl sPt.i.s. srLclr srbsl.nces nll' rcl..srd b\ iniul('d i.diyirlLLrl\ 1n)r jri\t.nr.! L.t . 1o eli.lt Üi!,ht rc..ti(lls ir1.on\Fc.iii.s "hor.nughl Ircd.lor) \l. \ oi thc jisl) kno\\'n 1o !:r.lninr sLrbst.rf.$ b.lo.B t(i thr ()st.rx)ph\si .nrl itis, thrrolorL', likrlv lh.l sofreoi lhrSoLrth.\ntri..nrl..tri. rishNill L.. .rd(lc.lt'Jthr slol islrsilh.hrfrr.il'drithcn(s.It.sfonsi\cnrsjn,.huri.nLs hrs brc'n d('scr l)c,l in arr,r//rrr?,rrr t,rt, r:n (lii.:er) l97l). Scy(r rl sturlics.ttcrrp tud t(i Lrsr.leclri. ilsh.s i bitnn{nrilor i'.r \ni.r (lLLrlii\ .(nlh.l. Whilc thcsr .ritcnrpls hivr. lirrllr(l Iri.tj.il Lrs! (s.. Nl( n lrr, 2(l(12), thc\ \Lrppln t thc rUtiori th.rt thr fish ,rrc Bo(\l .i (l.t(,.tin$ .hrrri..ls. Il.s.fil\., . rL)lc ot.h!rni.nls iri cLc.lr. ii:h.o.rnrunic.rti(nr hi\.ot Lrcrn drnrDsül(r1. H.sucr. elrcrrrierl nil ili oii(,r i rl.h p(ilrniiil l{r viri.ii(nl,.i1 (hrif n, pror1u.. (..9. Ll()ssrrt ird \\ilson, l96l; Ilus..Lrer\, l9trl)inLl lh..hc.rj.il(onrnrurrurlrrr.i d r()lc ol.hrfric.l 5ignils l(n lonrnrunj(iii(!r r.l!v.rni i.rsks hi\ Lr..f LlLrr(!Nhnt.d in\i orLs.(nrelL.tri.linr(/ilJr,ri,!rrii,rre.B.()lsen,1.)91,Inr^\r1IfLl Lio$n, l9!t:51, r. L|i)frrrtr,,r irrLl rr,rn , /rl)tr,',. B. N I.l .rni. inLl RFn, 1()(.r;; liclinsli et.rl.,21)(lli Shoh.t inrl \\Jlt,20i)+, rr,!iirti,rr e.g. St.1l.rll, 1992J Ii r(iu , ther!rtn(,brrithn\LrPlisi.git.l..hi, lish \\'(iu[1 .(it !sc.hdlkr]l sigrrrls.

3, WAYS IN WHICH OTHEI{ SENSORY CHANNELS CAN AID ILECTROCOMMUNICATION

Uii r.l..tri,dl 'igrrrls, ii'1r.rn Nrhans. nr.5srg.5 th.t..nn(it be den\t,rl b\ thc nrij.rit\ .i othcr .ninr.ls lr.l,inr.l..hrnr,..Pnns. pr(nrl(lns or shi,l,^!ir1g,..h(!,\, r.iL.rtjl)n., eii(\t\ (il nr(i\.nrcnt oi ^lso,th. nrrLliunr th.l irl.rlrtr.n;ih.ih.r.onrrrrnj.rli(!rsy\trlnsir.Ih...frI.r..!si.gnosrnr\ lo.l..tfj. ijslr (H.Fl(ins, l!)lis; Ih\.nb.r\', 1r)(12). On ih. othrr h.nrl, u'inB rl!,.h i. sjS.nls P(ßc\ d nurrLr.r (ii inrp(irLrnt.(nrsh iinis (lJofl(in:i, 1t)S6, l()lS, Itl!e). I. ih. ti)ll.\ifg n,.ti(rN I $ill sugg.\l h(n\ l..i.S rrultisrrls(,r\ ..f hr'lf ovrr.tnn. th.{ ,(nr\hiints

3.1 Signalljng Range

I1r thr I c'].1, sign.l: ol .lcclric lish .nn Lrr rcn.lll\ pi.kr.l op tI1rn n disLriLr oi rc\rlnl nrc'tur:.n.l h.lp lo ld.nt i\ .fd krc.rlizc thc scnder. Hiutier, rlrcll Sqriru nn.l \lollrr (lel2) trslc.l Lrr.lor \cll cor)ü)llerl l.rL\n'.rhn\ c()llrljii(nr\ .ri \\ hnt d shnccs n ilsh r.sprnds lo d schirgrs oi its neighl\!t it br.nrnc.l!dl th.t ojrtinr.rl sigf.llifs dirt.rr.rs.rrr ln thc ngc r)i onlr I I rr. Thr lnrs.r dishf.!s nrc oLrt.rlff.l s lth lnrscr li\h.rnd nr \\.rtcrs ot low c(,rLluetivitv (Squir c .rnd Nlollrrr l9El) .rn.l Nill prob.rlt\ bc srr.rllcr nr tht frrcsr .c ()a clc.hi.dl noi\o b\ othcr lish or llghlri rg (lloPkins, l.l7j) th. sr nll rdngc iounLl b\ Squirt..fdNloll(rls.onrp.liblrsithcirlirrmL'.rsurenrrnts()ithcc]t.hkiktr1 .rliLrr(l J lrnfsnrllli.s ilsh nn.l lhr clcctftireftfrh! thrt\hold ('i d rr..i\ing jinr (Knrdsen. iqTar srr.rlso tl.rsti.rn, 1986). 790 Canltruuicntian h Fish.\ Itlt':81

A simple estimate helps clarify h'hy elech.ic signats are not praciical to understand for which electric fis cover large distanccs. This estimatc is based on the fact that a distance several iimes ihe size ofthcsource the field of any cha€e dishibution looks as rhai of one of the fe\a' local sPecie an eleciric dipole (c.9. see iackson, 1962). Thereforc, io estimat€ the range of g!'mrs Po/lrrrv,'1l5 Produces a ricl an electric signal, it suffices to know that the strcngth of a dipole fietd decäys to its electric communication p. ihe! h ilh lne thrrJ now-' , 'l dr

(discuss spasnht. tt rnLtd be interesting to test wh€thersintlar far range effects could that of G,rrt dnerrrs also be d€monstrtriecl in Pdl/i,rvflls. be done r.llldel dim liSht con To sümmärize, Llsing souncl coüld be ä means to increase ih€ There are no dätä to su commrüication ränge Lreyond the short rante of electrocommunication. communication task in the P Erperimental proof, holr,ever is yetortstandinS. But atleast in the mormyrid point to siart could be lvtull fish Pd1i,,rv,1/s, sorlnd must be inportant in other $'ays äs well because it is varbus sensory channels n1 ä]so proclüced atclose ranges atwhich electric signals arebeing usec:t. Presently, 1982; Moller, 2002) 11 thc I se neitherhave e\'l(lence lor the merits ofacoüstic signals in terms ofenlarghg electrosensory chännels arc fi the commürictribn range nor (lo r{'e un(lerständ in which wa},s ihe acoustic channel r,ith noise should r€ ( änd clechical signals complement each other. ii th€ lack of faidlftrl elect upretulaiing the rei€!'ance r 3.2 Coping with Electrical Noise again reach normal levels

The elect c worlcl unclcrwate. is rloi silent. Lighhring is an important sourc€ 3.3 The Number of Pos of elechic noise in thc hopics (Hopkins, 1973), introducing freqüency colnponents that can stimulatc a fish's electrorecepiors and potentially It is a peculiarit), of elcctric s' conPromise iheir alriliti, to elecholocatc and also b communicate lvith role, serving both for comm electrical siilnals (Hopkins, 1973, 1988). Other elcciric fish in closc !icinlty can contrast io other annnals t'itl also be importani sources of noise. Many electric fish havc found u'ays to in an üninterr pted iranr dr keep iheirelecirolocation powers in the presence ofnoise. Briefly, the receptors and life long coniinuitY lea( inr.ohed canbe tuned to ihe species' d ischarge (Hopknls,1976). h mormylid the nat rc of theelecidc cor fish, the sensorl' system in\dved in elecholocation is gäied kr eval at€ is spread over the fish'sbod informaiion only when the fish generates a discharge (Metcr and 8e11, 1983). aj]d tcmporal distriblrlion of Manyelectric fish usestrategies io reduce the compromisnrg cffects discharg€s surroünding objects caus€ ofconspecifics have on their ability to elecholocate (Heiligenbclg, 1977, 1993). temporal distribution, the Partjcularly nell known is the jammhg nvoidance respolrsc of the South surroün.:ting objects and thei American $,a!,e t)'pe fish El.lcrrr,t,'ri, with continrcus sinusoidäl electrical 1995; \'on der Emdc, 1999) dlscharges. When h\'o neighbors $,ith snnilar fr€quencies mccL ihe one with minute .:tisk)rtions that caP thehigher frequencv \,vill nrcrcnse its6equency; theorre$'ith ihc furtherlower organisms) caüse in the tim frequencj,' ü'ill lo$,er its orvn. This separaies the sercling frcqucncies so far Mevcr, 1982; \'on der Emde thal electrolocation ls possible agah. 1992 \on dct Emde, 1998, f Another $.ry ofdealing \^,iih stront electricnoise could be to rccruitother The constraints impos sensc,r), chanrlels. Basiian (1982), recordnrg from tectal urliis h the South processing can be clircctlYd, 'this Americän fish Äftur'.,rot!s, providecl the first and only evidence of ihis (Schuster, 2000, 2002) possibilit),.ln his experiments, visutrl cues'rescuecl'the deteciion ofä movint intervals around 20 ms but electrosensory object after ithnd been j.lmmec:t by electric noise. Unfortunately, detecting the electrolocatior no direct LrehaYbral demonstrailon has yet been attemptcd wherein this Westby, 1988). StoPPmg Gr discovery would be relelant for either electrolocation or in a task related to signals opens üP the cxP€ri clectrocornmLrnic.rtion. Can,,lpfd1,rotl]s under jamming curditions (in wlich interval fronr 20 ms oler a \ elcctrolocation is comprorlised) h.:teed use visual cues to avoid coLlisions,for conseqr.rences of inter-disch. instänce, s,iih slowly moling obiecis? Itl{'ouldbe intriguint io test this in the active n1ok' and sensorY set-rLp Lrsed in the classic experiments by l-{eilisenberg (1973). ln doing so, discharges that folktr! after greät carc mt1st be taken to ensure light levels in which the is normal ones. Th€ $'a\'€fol operauve. For insttrnce, ifthe vlsual systemof Apfc,oolts would be similarto generäted ai iher no llal I r)frr. El.'.r?scrsr ri,it, Orr.r -S.,rs.\ that of Grrrrdr(rrrrs (discfisscd ab(\,€r, thcn the cxperinrenis rvout(l ha\ e to be done under drm light conLliLions (around 10lx). Thcre arc no cl:ria to suggest ttrat rrthcr s€nsory cha,uels can ajLl in i Lonr-ur.,dti.' rr-l I'ln./rp-e,r... t.r,.r -',\, t..t ..'stn. r,.." .\ g,,,1 point kr siart colLld bc Mollcr's appr)ach rcsardins thc respeciire ftn:ls of d,,,,* t- ,r llll',....:l ", " c.,, ;.,,r.,.,, ,\4,, e,(. ... 1982; Mo1ler,2002). Il ihe rcspectjvc roles of thc visunl, mechanical. an; , n., !.. t,.,rr i\...i, rrl i ,.rFl\i C- ,l Lrr, . I L,. I ee., . t. ..rl .h.. dr. ,\r11, r' r--.r',.r1.r',1,!e.,,tr*r,i L,l1r,Ji.L,l-, ,r,r.-..,.lt^s,\--, I , t .,.,t.,,- trr' , i, .r lr Ul , t, [r..,t iIr,r i. tF,.\lr.i . nd . ,)\ I r"-.rr.,l ,. ^rrrLrb.,rüd llt r). F|. \., .F,,t Lre..t r., r r,l- rn,rr gr. r i-r ,t\ .ro r.,,ul,i aganr rcach nornral le!cls.

3.3 The Number of Possible Messages

Itis a pecuti:rritv of clc,ciric sign.rlti.g rn fish ttrnfthe cjis.h.rrgcs fulfita cjoubtc role, se^'ing both k, comnrLrntc.lt('r as tr,el ns ctectr.otocat"nn. Mor.corer in Lo.,,r'n,, lr,.r.,nr',,. . \\ il.,.r, t \,. i r -.,r .\-t, r'l. .ti-, 8,.. rp8.. r r.,1,., l .1 .|'r r.,., rl, .rl.r,.t .l'rfl.! t., ri,n. -,.i., trr... B,rr.ir. ,r r..t rL.r -ri.r .rr'il, l,iö.,'r,l r.Ir\.,1,.i r..ir-1,.,..L,r.t..,r..t.,{,r,r..\..r.,Liitit\.r r, rl"'., 1I?.,t l\ , 1,.,fl .,,,,n,I, i.,, r^r,-i!r .,..l^ t...,.t .t..I.r8i..u-...n rl,F .t ,t.,,J\ - ,r,,,. .r . \Lll.ltr ri,l, ,,n,.,.Lrre,,,{-prt .,l and tcmporl I d istrlblr rion otthc iränscutnncous cun€nt. .ttt.rr'.r Irrom rhc rvav in whi.tr nr,'br,.. ,., .,,.,tt .t.rr1..- 11 ,r,;--- -a-,.r.,,-.1,.,r,.,t ..r,r re1 p "..l .li.t11h r.i.,r rh, r .., .,,, .,, ,.', , ei.!t11, I ,. r,lr..,.r rr,. -., .r,L.i'llrr ..r ,.,r,--r,.".-.t.,7.8.r,i.r _'1,1,' "'.E,,t1., t.,,M. .., loo: \ ar,l. lI,1,.t,-,.\,\.r.. .t,,t i-r,.rr,r..r., tLr-n-,r ,.si\,.\ rnr'rr Jr.,. r,'rF lt,.,t ...,,., L\..,,|rr.|-,,..,. t,...r'll,rr,,.,, .1. .,,i,," org.lnisms) caLrsc. h the tinrc coursc of tho transcpntcrnrat current ftot, tc.Jl \Fr.,. Ib2 \,{r.1,rttr,t...tJ/..,t ,h.c \i,n,t,r.,.,,o..,,.t Dt..,rl.,,Il. 1997; von clcr Em.lc, 1998, rin.rcyicü,scc \1n .icr Emde, 1999). The conshaints inrposcd bv continlrous signtrt gflrerntioll arlcl signat ur. .Irr_.,.nl.F.lr,.tl).t,rr,,...t..,te.1 nl,r,.r!r.r ,..i.trJr!.r,/r,/! ,.r), /< h,r\'-r.20n 2 f'r tl..|l.r r. rr r.:rrr I,r.,,tr,e.,.,r..,r,,rJr,. I rg-.,t inte^ais.üou.d 20 Ins bur pnuscs its otherwjsc continLrous ctischargiiig on del.r r'r.1.. (",.r. r,.,,t ..r'r.rl-..,,...r\,..r rt.l.-e.1..,.r. Lr,,t-.Ii..1,.. We,rb. s.,,Dtir ,-"., ,r.r. 1/.,. .,.r,.,tt ,6,.v 1,t..\,.r. ..tt. ,,t t,t': \r8rrr-.oP' ,r.,rf ll r\,'.ri|.rr,' p.^. ,r1 .\ ,, .rL.,.pr,\.r,,rr_,1i,.,.,rg, . r,r e ' , . , . , .llt, \.l'r.,',, '1, rr.,{, l' , \ . 1 . , , , t ' - n... ;t..2U.-.. J t..lu,r\ | r. or\ tr'1.. -. i rr.. ' ,lr- lr.r,;. r,h.,t,tr. ,jr..,.r ttr, ,. 11r,i,,.^rr .r.:,.-tl a lir, r ,1, .,',. djsch.rrges ih.t folkn"" aftcr ertendcd ht(,r!.rls dilfer h rhel. {,avef(, n from norn1al oncs. The tr aren,rn ls rcstorcLl (xrty slo\^.tv lvhlte clischarges are tencrated äi thelr norm.rl rate. A ctetlitccl analysrs ana intcrpretäft,r of the 794 Coiiltluni&t \1 iti Fishes Itltt

effe.l\\he"a,.,rändl!!r-i'rlermi,rqpenerdti,,,.doepl.tionmodet(trcte-. that provide examples of exci l06l. D.r.\ dn ird Rin/pt. tcoT,. eBi\en ir schu.,Lr(iü00/. ft 1., s"\er.-m siBnals and, in return, receiv generätion and ongoing activty are tjed iogether. This seerns to be rrue also and Krebs, 1978). For instanc foi processing of elech.osensory infonna iion. In conh.ästio rhe normäl situation the species specific female fl: wiih ongoing elcctricäl activüy, afrer experimentaly induced pausing, the males of these species (e. inr,,rmrriun -dmpted h) t,rqh .rL-qucr\\ re,;ftors -Dut not b\ to-_f;Juer; fatale wolrlcl first detect ihesii o me(hanr.dl rFLeplor.- rs n. ullecr.rDte t. modut,rre rhe ii,h.- n ecluuar) driven) lantern so as io pl päccrnal.er (Schubtcr. 2002, appropdaie for this male. W Under normäl operarion of the elecrric organ, the stability of EODS is clearly pales in compärison. impressivc. In a given individual, even rhe slightest details of tire wavelorrn discharges at high aleräge r produced äre stablc enoügh so thar the EOD waveform can serve as the 6sh,s Ilexibilitt at least not on a electric Jingeryrint (Craff j987, and Kramer, Mccregor and Wesrby, 1992). additional rlon-elechosensor \ hdr elFrrri, r,"l'.,re nbtc r^ r.,\i,rtrtc rdpidtv r_ihe intvti..r, rn" more rapidly. discharges fdlow eäch other Forinstance, discharges can be "ryariangea in anays to produce a variety jllüsträted ofsignats, as by,raspJ generatectiy malesäf 3.4 The 'Message Blend ihF n-,,rmy,io Bt t, r,,,.rru,i,r^ |,ttrttt- durinä,he briding.ea.on wh,n a rrpF , a particular comn l-n.r h Pd $e- h) HopUn.. lqso i. R".p..,re -tereotypcd bu ßr" com pr\rnß Whenever r\u d \chdfSi\ per r.rond dLr \Fredul,t,, 0rrme.:naminute trrav+1pi signals to pass, then usnrg elecrri. fr.l- ,r,.,t pr,,r,uce , nu.oio.rt cli*hdrgc., rh, rrequen!) .an';e attractive, brit presently pln An modulated ioprodrcc a varicy of conmunicaiio; sjgnals (e.8.'Hagäorn and ctisiinct messages. organ Heiligcnberg, i985, Engleret ä1., 2000; Triefenbact, o"j-Zuro,l,iOO:y". Vor-yr;a severai chaNlels could gäin fl ri5ncdrJl-o,rno thpdi-ndrSL-or i leirhborinS i-r, hithdi_chdrgc_ot üei: carrying a particulär meani nwnrn|,esFe(horF-D,,n.""(,,rtrFt,-.edtä,(.(yr1,.pon.er),.,frchdi)Lharse. biending' would allow new ,er .h,r! ä lin-,..ruFr d dr-ch.rrce or it. npi8.,b;r tor:g bpt.re rhe nrighboi r simultaneously sent messaSe r(\rJi".,.,rte,Be Fr .,t tu-4: BdLFr Jnda..,m"r rw,r. HerrrgenUeri. trz+. of distinguishable signals: Suf justsend 1976,7977j Ktalaet 1974, 1990; Schusrer,20itl). This re.tuces the risk of could one single typ r, d.LhdrSi',t ui lhe n(..r di.c,r.rrB,.ut rh, ,,eightroring rish, h,jl .ourd of its multisensory capabiliti( .ddrtronallvbFrs,\ ro(,,mm,.rrcd,p n,pofl.r trnr;rrrJrion"thJrhepresentty would then be only able to ! signä1s as packages simulian \^edll\ pariicülär blend of signals ha , elecrri( rr.t. crrr ch..nre t\L hirer,,rm .i the r clis,h"r8e. Su.t ch.rnÄe\r1hd\et.,rmo..rrrtritl,iImir,r.c...p.,\prat te,\t \.\ crJl h;ndreds numbcr of 2" - 1 distinct n of dischages ä\,ailabk (e.8. Hagedom, 1995; Franchina and Stoddard, 1998: Carlson er enormous Potentiäl J..2000 lcrleth iId Moll(.r.2du,:-ee st..JJdrd. rt-i- !otume/. H.,h pver, the-e sevcral chamels. Considerinl e\.i,inq, ., ,ll\ a ,d en\ and acoüstical signals, electrj \i ir,, meIt.r ) ;ndu.erl \ Jndtion_ _houtd be put rn per.pe!lrve. 'messaSe Ior.niJn.e rhe Di.r{icrr} b.rrn rod;r. i. nor"u.tr.r_ to jt.ow could benefit from cn.FJe!trirdll\ .i81,\llint r,,1 model to tesiwhether animall ri.h l^ nro.,u,e . di, harge ot trJ\erorm A. fol'oo eo .'ne nr,r a sitüaiion with h{o siandar b) dr.rin.r u ar L iurm B. one or *aver,,im t änd lhe1. ..,y, bdcl i,' A ä8.'rn. Th,r Frl fiied type of eiectric organ di c "rF rr, s lv di-.h.trcrnB (te. rri. fi-h tnown thät Lrn -t\ ilrh belw.( n dit-,rcnr the three combinations (soul "rgnrl r1pe, rrorr one di,!hdrB- ro lhp rc\ r lf this were indeed the case, fish could emit dishon"est signals. Howevea distinct responses. rn onc l,d. d,mun.h.rte.l rhI etect- i or8an, ..rn br .rrrecredio prnouce ,a\e s-gn.r< ro , on\pe, rtrc-: tor ir.t.,n,,. J smä frjh produ.ind dr.ch,rrges lhal 3..5 Localing the Sender mrmicalrrSerf.h.or. lrrt,,nr.rteß.rinrnga*e5.t,rJrenit,,rvb\mimrctins How does an electric fish loci fcm"lc d.chdrBes fhi, confn.t' hittr noi-cte, rric .oln-u,,i,iion ,r +"rrl conrrasi to visually Suided ( --r

Itrttiftltxrt trl tht EL,.t1)i.rs. if il, Otr.r -Scns.{ 795

that pro! ide ex.mphs of cxciting nrnrs raccs if \\'hich scn.lcrs ernit.tishoncsi \ignals and, in retrurr, r.ccilcrs cle\el(]P mcans to deted thc chc.iL (D.1r,kms and Krclrs, I976) For nrsi.ncc, icm.rle lircflics lirorIrls (l.r,r/,,s liirtrs) mimic thc sPc.ics specific itnak flash oi other lifcilY sPecies kr .ithact and deloru the itl.s of ihese specics k.B. Llovd, lL)75, 1983). ln ihls bcha!(n., . tcmme f.t.rle i! ould first (let€.ct the signnlot th€.prcr nrale ancl iherr sct hcr orcurcnillv .r-i , r' .r L ,,r...r1r.- rtr, ,t".i,.. .t,., r. r."rrr,..,.t.. r._, .ppropri.lic f(r'thrs m.rlc'. What s'e kno\^,.rbollt iish electrocomnrLrnicatiül clearlv p.ll.s in compnrison. Thc nr.rchinerv h) Proc:luce ancl .lctuct etectric dischargcs at high alernge ratcs nrav iLrsr not bc suitable to.rlt(,r' f(tr such ile\ilrilit)r.i lcasl noi on.r snr.rll iime scalc. n) achie|e su.h flcxibilit\,, ..d.1 rr. r"' - 1..tr.."r'-. ,,:r,.,1,,.,..1, I,,1.r ü .n\r\ r.r.t, nx)re raptr{l\'.

3.4 The 'Message Blend' Hypothesis Whcnc\o i P.lrticühr conrrrLrfic.rtion .h.nncl .llows onlv a limited set of .r'. .' . "1- rl|r ., r; rr r ." 'r, attrnctivc, bui presently pur(ly hvpothttjcil, \,.rv io boost thc.umber (rf distinct nl.ss.gcs. An org.tnisnr $,ith the opii(11 to sjnrLrltancouslY ncii|ate sereral ch.rnncls co u ld gih fronr h.fsmitting.r 'trk nd' ot messngcs,..ch btend c.rr\'irrg d Particul.rr nre.rning t,r th€ rc'.civer. In oiher rords,,nressage blenc:ting'rlltrrlLl allos,ne* sign.ls to be forlnc.l iom the comlrination ot snntllt.rneousl! scnt rressigc\. UsinB sUch. blend {o ld increasethcnunrber oldisinrguishiLrl(signals:SrrLiP()sc,iorinst.rncc,rh.tca.hol,rserrsorychinnels could jLrst scnLl (n1c single tvpt 1)lsignal. Aspecics th.tdoes not ttrkr a.lvanLag€ of its mLrltiscnsory cnpnbilitics itnd scncls nnd rrri]lyzcs the signnls srpararety \..1.1 l.,e',..., 1..,l ,.. .. .,.r,rt.,r.-.;.... t,,".'.r -.r.ti, g,. -JL tl -...rr Ir.,..I..\. | . Ir.r., l ,rr1.,,,.,1, n_\,t'.| . r . . , - , . r r | | , r . . :, .,.1'.,,1,..,,.,.,,,r ,, \.1, .t. ,{, tt" n,i t. 8,, iumber of 2" 1 Llistincl mess.rlicsl This sürple rt.rs(Di.g illLrstrntcs thc cfornro(rs potenii.l .\.ilabk k) nnnlals that c.n coDllrinc iriormltn)n fronr sc\ cral ch.lnnels. C(nsideriJrg thc stabilitY af(l the simpli.iry ol their €lech ical rr.l acolrsii.nl signals, elcctri. fish, $ iih scver.rl sensory channcls accessiblc, , r.ll-,.t. rf,,, '",^. ll,r, mod.l kr i€'st u,hether i.inrnls nchr.rllv usc it. Slrch.l iest &)uld icl€atlv nr!otvc r.".'\.'1, r"., ,.1.'f../p, .iir.l . .,\rr.r ' . .' r\... )r,,.,f .,,.1 . fired tyFc oi electri. (ngin clischnrge an.l ib( n re.tuire thc .lenr of si raiion th.rt thc thrc( conrbnr.rt("ls (solrr(t onl\, elcctric o'rl],, sound .ncl elccir-ic) etj.it

3.5 Locating the Sender

How does an clechic fish locnte n signailifg neiilhbor n1 ihe dark? ln m:rrkcd cofirasi to !,isually glrded oricntation, ii is difficult for rhe fish ro ässcss a 7r)6 d)tlihtlniüti,t i't Fi.h.i

sender's position bäscd on eiectric signals. This was lirsr demonstrated in the from an electric source Whair nDrmy cl fish tsr;rrorrlfirs 1,,7./rv^rirs: When Schlüger and Hopkins (1987) in thc dark? What about fish used dipoie elechodcs to playback signals thai mimic a conspecific intruder preditors or i ggre\\ire .o n\Pr ihe holder of the tcFikrry $,ould approach and attäck ihe sending elech.odes. ihe meins h' raprdl) dLL€ct tl Hoü,cver, it.:licl not ss'im straight towards the electrodes. Moreover, when integration coulc] bc l€lPful n ( ihe orientation of thc diPoleelectrodes was changed, teä\,jng iheirspatial center ihatf(rra clear d€nxnttl ati01 consiant, thls gencräied completely different approach paihs.It became ciear to elimlnate äll othcr non-ele that ihe paths taken by an approachhg fish are notbased direcrly on rhe spaiial h'erc not only carricd oul h d localization of the scnder but, rather, or1 something very differeni. The fish,s oiher informäiion t'as elimin stra iegy became evidcn t when Schlüger and Hopkins compared the respective about the whereabouts of iht approach paths with ä nrapphg of the electric field lines generared by the presence of ot ienting asYln'n€ source: The fish approächecl the elechic source simply by fdlowing the field ;rd misht have contLibuied li r',: I hr. lrn.i||rt h.r, oL-n, ofl .bor" ed n iu-lher F\pFrincnr. b\ Dd\ i.aro (1988) and Shieh et al (1996)( Hopkins (1988), Hopknls (1993) and Shieh et al. (1996) in the gynnotiforms (1993) on ihe oiher' To r€soh'r Cttltltloltß cnnpa, H:lpopt liltsLliuica tLtt s and BrnchllwpopDlln$ diazi.T]Ireanly be usefulof ho$' thc availabili .hro v lh.,lch.rllenSed rl'i- \ i, tr r.,r \h^rt r, p rr b\c( ddm,,L,rrdM,L,.egor ihe line-f ollo\^'ing strategy (1993), \ ,ho reported that Cln .ttus ütrapo is able to choose ä slraight iake-off Visual (perhaPs also a( djrcction to the soüce when a familjar signal is sent, but a more'cautious, dir€ctionaL hearnlS in electr cuNed path when the source emits an unknown signal. Integrating this with conspecifi. or a prcdator cotll the fnrdings of Flopkins, this coulcl onlv implv thätbesides ihe line-follo$,ing The electric sisnals $'ould thr shategy adopted to approach ar unfamiliar source, the fish would be abt€ to subsequently directed bi/ \ compute the position of the source and use this äbiliiy for straighr approaches landmarb in the surroundin towards ä familjar source. Ho{'ever, it is difficult to imagine why rhen a on an insect acoüsticalsystem cauiious äpproach should follow ihe field lines. A lish rhai is able to compute ho\,v thismight lvork.In Phar ihespätiäl locatior ofa dipole source coulcl aiso use itnr phnning its caurious of sevcral seconds and ihe pdlnd|d (,.rlo lhc-prore 'lor h, f^',(o io,l-oo,Fü're th.,l foll;h-rhFfictd towards the female BecarLse lines. Unfortünäicli', Scudamorc and Mccregor (1993)did no$esi $,hether rhe response to ihe hfre$cni m cautious approachcs o f their G yrr?otrls lish also followed the electric fietd tines. clres are availäble and, thus, L The line follolving shategy of eleciric fish is an interesiing exampte of a As $,äs expccted, the male'r closed loop behavn) nr r4rich sensory hformation is continuously evaluäted en! n onmenial cues than the to permanentlv glride nroior corrections. As soon as the sencler falls silent, the wiih optical .ues in any fixe( searching fish is lost. Convcrsel],, ifthe sendnlg dipde changes iis odentatioq is able to adoptan imPressile Lc. ppro.r, h rr\ ri.h inrrr, o ,,.plv bpnd- n. s.) L.,t. li8r- iiwitn Lc\ r.rnged sinilar in an electric commur the s( iic d lir.e- \4oreo!p . s rc, tu..riofl ,l ri-'r .re r( t eJiedlv, h.rll.ngcd rrom a any abiliiy to compuie constant source, fixed in space and with ä constani orientation, iheir first of the landmark nlformaiion approach looks jusi as the 100ih and shows no sign ihat the fish colrld its line-folLowing cource r('h( eventually s(im siraight to the source. use landmark information h Prcsentlt r\'e do not have good reasons to assume thateieciric fish carl do and correct iis cotlrse as nei morc than follo$'ing ihe field lhes to arrive at a signälln1g conspecifi., which coulcl further assume that lal .d. r.rrpli,rreo curvature ihe moment i- rn, rr $ Lrlroll ro " rirl.er problenr. But rr 15 Jow. I r5t body because it lcäds io clrrved an.:l hence loiger thannecessary parhs and se.ond, continüe iis curved Path Th beca se it requnes cortnruous sampling and evaluaiion of sensory data and provide no conpass bearhg continuous corrcsponding moior corrections. One ra'onders wllether there are approäch of the ftsh lnoreeffi any options for clect c fish to speed up an approach or perhaps an escape source, ihe fish could eventui iur .)f elr.lrk s(trr.r. !VlLrt nlnnri cl..i(rsrn.iti\. fi\h lh. t hulrt rl.'h itj iish in ilrt dnrL: Wh.rt nb(trrt ii\h lhil iitcr pl l,).{|Pr lrlifr clc.ttic.ll\ r'tivr pr\lnnJrs or iggr'!\s!\ c.r!NPr.ll!.\? I:s.rt) ng lish, in P.rrli.ulrr, should li')\ l' it,","""n. r,, rdPi.llv Llii..t thelr r'.rPcs rrn\ tr(!n r scndtr. l\1t lli{'rlsor\' mtegr.rt of .(,uLd Lrr h.lftul in nchi.\ j g ihLs SLul ()|e:houltl k.r'f in r)rirrd rhit i(n.n cl(tr .l.nronslritrnj oI lhc ljnr h'lloNi.r strntog\. ii $ns in:lNnrcnt.rl to !linrin.rlr rll ('thrr n{!r tlo.lric sen\(nr cte' Tlrcr,rlor., lllc o\Pl'rinrcrrts $oc not rnrly .rrr !.1 .rrt j rlrrLn.'s untlor nrfifctl illLrnri..trnr, Lrrrt rL\(' nll olher irlorn ii.n \n5 .linrirl.rl.d is t.rr ns Po:sil'lc th.rl c(iultl frft\ i'1' ..uos iL.(utihcnhric.rlr(Jrls(,ttlletost ish I:.rnrili.riiY $itl) lhe n'st tilfk in!i th! tre\tn.c ol .ricntifs.s\ n rttri15.il hi.lrln.t(nsih.rt.rcdiiii.Lrlt1(i'('r1h1n :nrl nright hn\t.o.lributcd to Lhr Lljli!rrnl rcsuLts oi l}itrs anil lirPkins (19SS) nrd Shj.lr ct nl. ( l9t)(.) ('n thr tnl. ll.rn(l, .rll Seutlamorc rncl ir'1c(itcgot

{ l.l9i) on ih. othÜ T,, res()L\ I lhrs Llistr.Pnnc\, if nn.rlvsis s1trrL.l, lh.r!n)tc. be Lrsr'lrLl (ii h(tr\ thr nviiL.rbilit\ ol n(!r clccir'()sens(r\ ilrlinrn.t()l] c.' ai crrd iht llf. l{rll.( ir)g strih g\. VlsLril (ptrhnp:i als(i n.otLsti.rL .Lrt's Lrui Iiothlfg j' krrotrn dLi('tl dirc.tlonil hc.rt .s in clccttlc liih) tlrrt cfr.nntc .lircrtl\ irum . Llistnft .ofstr.ili. or n predrnn t.tLl.l hrlP n, rlite.t th! .PPrupri.i. nrotor rcsir(üscs' lhe €1..h ir sigfnl5 \1Nl.l tho r tnrlY bt nccdrtl to tfigger thc lcsPonsr thrt is \ubscqLrertlr.li(.t('d b\ \isu.l .!rs. lnl'ornr.rtion plrviderl bY risLral hf dmir ls if the sumNndif !,s... .rls(i Lrc \ rr\ hclPlul. Restrr.ir.arrictlotLt on.ninsc.tncoLrsll..l\\slcnb\v(trll!l\rrs.rr.rrrd\\rn.]lcr(2{)ll1l)illn5trnt(.s hoN ihis r ighl\ or l( hiPh.ftJl'tuirrcbLsh'rklcts,lhcnrnlt'nlls'Li'te^'ls ol scvcr.rl sr'conLl\ rnrl thr lrnrdLc r!\pord' \ith cli.ls t|.11 ctLr thc m.lr lor ir ds lhc i..1ilc. Llc.nrrs. ih.\c.l .k rrsPorrsrs .rc shor t nn(l 8i\ cri orrlr in l!sp(\i\eLoth, inirc.lLLlnL nr.lr.rlls, lh nr.ltnrtslnr.\rshcnnon.orrsii' ru.srrdn\nLl.Lr[.r].1,thtr\,u{. op(il(\iirsn.rtrg!ir)nfPl1r.rl:hthc50rrr.' ,\s \.rs r\t..t.d, thr nr.l.'s L.ursr i5 sh.rrgl\ nrcindrotLs Ih.rl rro olh'r .11\ irofnrrni.rl , ues thni th.5l(nt.i!.ks (,i tl1. torI,rl. irt n\ nllnl'1. llo\\c\'', \ ith ottl.rl .!rs in nnv li\.f sP.rtlnl r'( liii(rr to tho i.(ustit: sour.., drr nrilc i\.blolo..l.Pt.rrirIprcsri\cL\\tlJlghtrPfrf('nch.c.trrlJ$rc\f..tn'rnrihins \irnil.rrinancLc.tr-l.cofrnrurli.ntlonsv'terrllllrrfrobLcnrheri'tlLrtNiih(iut rn\ .rbLlit\ nr ronrprLlr tlr. s()Llr.r loritjorr, thr fish .rrrnoi nrili. ()frllfül usc oi tbr l.rnLlnr.rl niln.riti(tr. WhnL the iish .orrl.l rl., hoNr\ cr'' is hr sLal'iLiro it\ I nc l.llo\il]g.oLrrs, n hrn lh,. rl..hi..11 sorrr.c S()L's sllr't' lt Iotrld llltrr Lrse linLlnrnrl iflorniti(!r t(i kc'cf ihc Lrst dir..tiof golcnrcLl b! lLeld lirics lnd coüI,(t its coLrs..s r.s ilcLl linc inf(Jtnration b('conrrs i\iil.Lrl. Orr€ .orLld trn tlrcr nssLrnr. th.t L.rnd nrirl< innn nr.lio11 htlps thc fish tr) nr.i.i.riri its bolly.nr \ .rturr lh. nlonrtrri thr ii.lf i\ s$ ilch( Ll oil, thLrs nll(r\ irrg lh. rish t(r crnimut its cL nrtl fmth. lhis $(iultl Prob.Lrh trt dilfLclrli $hcn lrntlnr.trks prr c no.ompr'. lrc.rrinss. Il(,th rtritc:l(s ,ould bc,lcsigrrcrl llr nr.kr the rfpr(rcho lhc tjslr )(,rr ctii.i..t. \l('r-rorcrl \ hcn.lllo\.tlni ru.ch lht sisnnl .our,:t, tlrc lLsh erILrltr tttu.]l\ rdoPt r strii:lhtnPp(r..h trscd on Lrrrdnrnrl 79a Ca l Lni Liatl in Fishes Lrt4 information, when the same soürce is activated several times at the same fish employ simple shategies but älsc location. Mnltisensory nlformation can thus potentially ädd ä number of usetul landmark orientation consPecifics. Visuäl motion ( trick that, in combinaiion, can Suide the fish in rnuch morc elficieni ways la towards än eleciric source. mormyrid retina and could Acknowledgments 4. SUMMARY AND CONCLUSIONS Ii is a pleasure to thank Peter votume and for his ediiorial he Reichen Electric fish frilfill thc pr€requisites ihat quali fy thc'm as aih aciive model sPecies Engelmarn, Andieas to explore the bencfits of ä multisensory commünicaiion system in a well- referee for their helPful conrn defined neuroethological tuamework. Most electric fish have flrlly intact non' eleciric sensory systems and a closer look at the conskaints imposed by electrical commünication suggests varioüs ways in which adding non electrosensory signals may be helpful in oPtimizing their social inieractions Bästinn, J. r982. Vision and electror I argue that the dual role of the electric siSnals in the fish's active tcctlm ol the weaLlY electric n elecirolocadon and communication behaviors limits the number of messages Basti.n, J. 1986. ElectrorNePtion: Br Bullock änd W l leiligenbcrg (e that can be sent. Additional non-eleciric siSnals could be added to increase R. ,nd B. Kraner 1974. ASonis pLrtative mültisensory Bäuer, this number. with such adclitional siSnals, a the cleclric orSan discharSesol communication syst€m of electric fish coüld take advaniage of combinatorics 52 to boost the number of possible mcssages: 'siSnal packages'coüld be formed Bell, C.C. 198r. Som. central connecl in which the message is encoded by the particular blend of si8nals seni ln: Hütittl r dSa dCah (eds.). springcrvedas, New Y( simuliäneoüsly across several channels. Electric fish would be ä model tood Bell. C.c.,I.P MYer and CJ RUs*lL 'messagc does indeed occur in multisensory system to test $'hether blendinS' rlat€d beh.rioml disPlays in ( communicätion systems. Localizing a sender is a key ability in any communication sysiembut this Bc.souilah, M.ändi'P Denizot r99l is challenging for electric signals. Wiih only electric cues available, electric and immunochenical dcmoN _114. fish follow th€ field lines to gct to their signalling neighbor. This is a safe but N."/os.,. 3: '107 Bleckmann, H 1993. R.le ol ihc la needs rather slow strategy. Moreover, it is a closed-1ooP strategy that Pikher (ed.). chaPman & Hall continüous information from the sender if ihe sender goes silent, ihe searching Bleclmann, H and R Zelick. 1993 fish is 1ost. I sugtest ihai this siraiegy can be reädily imProved by using lateral line rnns of NcäklY ele, addiäonal sensory cues that enanate eiiher from ihc source directly or from Bosse.t, WH. and EO wils.n 196: tsia|. 5: 413469 stationary environmental landmärks. I Thcot Bratton. B.O. and B. (Janer 1989 I far, is known Electric fish are sensitivc in deteciing chemicals büt so noihing spawninS in thc mornl,nd Po aboutthe use of chemicals in eleciric fish commurlication. Regarding hearing, Braun, C.S., S. Coombs and R R FaY a challenge isrwhy apparcnily so few electric fish äre vocäl, alihoriSh Probably o.tavolaterälis sub'systens? 3 all häve excellent hearing abilities. Here, a sensory ecological approach would B.o$n, G.E and J.A Brown 1996. be ne€ded to estimate the äciual benefiF and costs of sound communication 219. Carlson,B.A..C.D l loPkins and P 1r und€r naiural conditions. in th. el€dnc or8an discharEr Among the non-elcctric sensory capabilities, mormyrid vision aPpears to t77 ta6. be the most promising sübject for the near tuture. New findirgs are beinS Cartaright, BA. and T.S. Collet r! Itvsiol 15lr 521 541 made on the struciure of th€ mormyrid retina, new visual PiSmerts havebe€n Co 4, Gonlon and P Moll.r 19 proposed and ihc seärch is on for the tasks ihät the mormyrid retinä is Ciali, S,J. C,nlli!tr.rrß nsin8 its sense P.nrrri specialized for. Vision is a frinctioral and Probably imPoriant in Hid 50 107,F1087 mormyrid fish. Despite their low resolving power of or y about 3 degrces, the fish cmplov simplc strniegics of pittern rccognition Lhai can bc useful for l.ndm.rrk orientation but also f(t cletecting species stccific \.islul matks of conspccifics. Visual motion dcte.tion could be the major tlrnctnrn of ihe nnnnrvricl rctina nnil coulLl largely cxterrd iis useflrlncss.

Acknowledgm€nts It is.r plcnsrrre to thnnk Pctcr \4ollcr for his ifYitation k) contibutc'to this \ ollurt än(l for llis eclitorial hclP. Inlso thank Gerhard von dcr Em.le, Wolfgang Engclüunr, Andreas Rci.lrenb.rch, Otto von IJelverscn and än .rnorlymous rufcree for their helpful commcnts on the mnfuscript.

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How bees remenb€r flower shap€s. Scrtce 227: \492 1491. Krudsen, 99, 103 118 C.aft C..nd B. Kramer 1992 Trained weäkly el€ctric lishes P.lln'1ltts ßidotirndc atho ü ts fl'r iol p./.rsii (Mornyridae, Tel€ost€i) disc.iminat€ betwen wrv.forms of electric pulse discha196. Ethalnli! 90:279 292. lüh':a/llt^)| of tlt Ell'ttrasürs. 'itir Otlr.,' Srrrsrs 80] ll.igd.n,Ni.r!!r5Th.flL.hnaiihrrr4r,iLxrh..ri,l,Jrllrlß.nrnrf l!n ul.rt! lh. im!titttl. ifd du'itnnr.i it!.L!..tn. tr'B.n dis.h.l.gcs nx, tn'/rr l9: Lll)9 I]li ll.g0!1.n, \,1 rn,ll! lll.ilLg.rbriA l9lj5 Corrl.fn sfJL: r_n'.ki. sLAl s rr tlt.orrtshif rnli nr*ing.t g\nrn.tLrJ anh ,,lrn, l,t,r '13:251 26r ll.trn\,(;.(;.ind\!.A \.r llc'lfijl l!r,2 I\d.n.. thnl th. l.rlü.1 Life ,tr8nf .('iPo.ds nr nlir irrld dispL.r.lnr.nL: .t :.!.J s.u!.ri nr trrtr'l / l..,tr Si( r,J ll: ls3l lsll liiüglJi C. rt, F L98r lln numtdd nr.slf.rFhiL,s Ir rri !!lir J.r{il r'rlPrß fI tll' l(n!:r.mnf.nlnL\nrri.!ftin,l.tir.nl..nn.!tnf$*udL.dw1lh1lr€HRlnetri Jn",r ll.n\(rs,,\D l!nl Th.h.r,inU rbi rirr\ 1,1 iLsh. ln: l/.t,rrt,'r/sdn,l(:.rrrr,rinrktr nr fiilL'i, N\ l.\.1!i,rrN n,f|lr nrll ltlt l:.r! (.ds) 5prlfgeF\.rlj3, Nrw \itrk, PP 10e l3i ll.iLiA.nbrrg, W !r7rr 'Flr.t'..r,1or'r.rF.fsf i. th..L..tn. lish Ir\,trr,,r,n, (Rhi fhi(hthrnir., (:\mn.nleil lllr,rt (lonJ,'1) 2li: 301 301. llriLisfn[.rA, w l(]7.lLr ll!.t'.l.rrrr.r,i].bj!.ti rn lh! eLe.t'i. Iislr rii!.rrnr iir (lt Lmplri.hlh! ]d, (:\nnntnl.r') I (,trt'. r'rrlr.l 87 I17 l6{ llr,LiArnl..rg, !\j LeTl fl.1ta,lt).iti.. and j.mDing n\oi!1r... i. n llrlofrr!t (l{h.rrfhi.hthinlrr, (^nmirtiid! l, in cLr'.tri. lish \id, pLLs. tvpc.lis.harBrs 14,,,,, /)/,v{rl ql: 223 2li) Hrili!.nti.rrj, w. lLr76.lll!.n1il().ntnn,rfJ i,,n'nurgiv.dance r lhe nt{nry. li:h /nlrrLrrwrr I 4d,4,. l)lrvnd/ lll9 157 372 llol,Adb.rB,W /r,rrtr,rdi!:l,.rrndnrrrrr,,,i/, l.rt7 "rn,r,t.0i.t,!r,rr:l".r,i.lini.SPringer Hliligob..t, W I9tLN.rnriN.15n,fld,r'/^, NIIJ lt.ss, Crmbrü8., NlA H.u5ifA.r, C.li lli26. tl.nrerlufg!n LiLrr Jr\ (;rlrii l!rkzctr8 des Md,,,r,r!.!|,trinlrr, l;nfult..r. rdr4r,i5xr !r(l |r,dn,l!r ru,,ni /is irlt ,'it,r rrl1!!o/ I :121 r27 Itrklrs,CD lqtl s.\.l,ai.rt...s nr.l!.1ü. signilling in rn.lt.ki. nnr^'l,t/?/ S.i.,. 176 1035

Hotlnrs,(:l) 197:l LiAh{nnrg is l.r.kg,ouf,l n,,is. hr..nrnrufi.ntnnr aDrnrt...tri. nsh \drrr {Londrn) 212: 261 27n lk,pkurs,CD Ie71 lll..ni..,mnruri.rtiilr l'Ln.ln s in lhe so.i.rl bchn\ntr.t/i\.r,rt,in .!"n1rr JntlrJrrr -l) 270 105. Hopki's, ( l) 1976. Sli.r!lus filtrrin8 ann .lrct..r1.Phon: h'b.n\1s el..trot.ePt(trs in thnc s||tn.\.f FlnnnnLd n\h / L_{'u l'llvlr/ l7L 207 Hopki,r\, a.O. l()li0 [\olutnr .l c(..tri, .o nhni.ntn)n^llL .hannels of Nnm\r s ,n/!rir f.d].

Hopknrs, CD lrlsl' So( L.o.nnuni..lr.n in lhe.qu.ti. rn\i,onn\r.t. ln S.rrnry Fn,l,].(r/ di :l,rx,1r, ,4rnrr/!,J.,\trnr,li R fn\1A N Porr., rnd V\ N. IJrolga (eds.). SPringer \1i1,,8, Nr\ \i)rl' pf. l:13 263 H.flnrs, a D. le9r. N.uro.thno$, ol fAsr. .l.ckol().ntrm. / adr+, frvlJnl A 173: 61le 69i Itrpki|s, C D 1999 D.sig. i(rtU.s nn .l..lrr. .onnnuni.ati()n / E1,], /ji,t.202: l2l7 1223 H.fklns, Cl) r..1^.1t. ßnss. l!ll TempoDl.o!i.g ot sp..G r...llnition siSnals in €le.tri. flsh s.rrn 2L2:135 87. Jtr.kron, J D 1961. alßlinrl a,,1rr'rrxdu.! J,,lrn wiLc) & Sons, New York Jllr!., L. 1e7,1 Geru.lrs'./.ftnn nnll hitl&nngnrkln ila t b€i dcm s.hsä.h rl.ltrß.hen [rs.h L_r rirrrrr!r r,.ri,!;; l(itrr 1862) {N1(tmtrida., T€le.stei) I)issrrtrtntr, S.irhü.Len Kal.rijn,,\ | l!88. l\drod!n.nri..nd acousti. lirl!i !lrtc. tr.ln Sdrrd/r/ EJnl(r,,/ A,ßdrr. /l,,rrl!, J At.nr, Rlt. r.tt A\ IllTf' i..1wN l.\tlAa (eds) sPrnrge. \.,1.,9, \rtr

Knuds.n, E I 9TasfntiJLn\p..tt.1th..lc.ni.ii.ldgrr.'itrnh\Lt.kl].ldtri.tsh./L_r,'f j'rr{,/ q9:103 lL3 802 Coüultunicalian itl Fishts

Kramer, B r97.r. €lcckic organ discharge int€raction düring nitebpe.ific a8onistic bch.vior in Ols.n, K.H.1992. Kin recognition i fr€€ly swimning normyrid lish. A methorl to erälu.tc hro (r mor€) snnultaneous hn. Hak (ed ) Chnpnrn & Hill, sedes ol events with. digitnl analvser /. Co,rf. Prrlsr,/. 93: 203 236 Pfeiffea W 1977 Thc.lishibution Krrmc., ß. 1990 Etucttu.o r rünatit l tt 1lltsr Fittr!. Behaviour and Expüinents Spinger Popp.r, A.N. 198r. Compamtne ! Kran€r, 8., J. T,utz, and H. Markl. 1981. The EOD sound response in s,€akly clc.kic fish. / cPithelia in dre teleost saccuh Co,4,. Prysio/. r43: 435 -1.11 lopper, A.N., R.R Fa!C l'hitnnd Lndich, F 1999. Di.] audtory scnsitivity and vocalization eloh,c i.d.p.ndcntlv in otophvsan of tel€ost fishcs lni i,ülPJ fishes? Rfin, EdmrL Edl. 53: 288-30.1. (eds.) Sp nSd VerlaS, New' Ladich, F and .H. Bass. Sound Beneratdr nnd ..ousti. perceptnm in aguätic v.rr.b res. h: Pnzd(x!sk1, R.L. 1939 P€riphcral Fislr Hdrnr!, S. Colin Gd ) SprhgeFverlag, N.r! York. (ln prc$). in Eoldfish, Orrsst,s dfurt,s. LazarC.,S. Liborban,and rSzabo.1984. Thenormrrid mcs.nceph.lon III Rerinal proiecrions Ri8lel,, L. and J.A Marsfall 1973 in a wenkly electric fish, Cxdrr,r.,r/s t.nrsü. /. Cd,4,. N.x,?/. 230: 1 t2 f.rrr.t (Pisccs, ). Llovd, J.E. 1975. Ag8rcssne rninicry in /r.tr,t fi,.eflies: Signal rcperroircs by fcmnics fatates. Ronachci B. r.d U Dull. 199rj. Ar S.rdr.c 137: 452 ,153. in h.n.ybees. I Cd,4, Phlsio Lloyd,j.E 1983 Bdümin€scence and comnrrnic.tion in ins..ts lrr.l?c,. E,rd,oi 28: t3l-160. Roias, R. and P Mouer 2001. lvlul Marvit, P an.t j.D. CrauLid. 2000 Aüdintrl' thresholds 1n a s.und-prcducnrg ele.kic lislr mormyrid fish, Cnntl0rd,rs (arhry,,s): Behavioral m.asürcmcnts ofs€nsitirity to tones rnd click trains / A.o,sr 5r and the passilc,nrl a.h!e el A t. t07: 22A92211. Rooncy,Dl.,j.C Ne$rT Szabo, an! Mccormick, C.A..nd A N. Popper 198,r. Adirory scnsitivity and psychophysicäl tlningcurv6 bülb in rhe w€akly electdcfi: nr th€ elephant nose fish, Crnthoüaü s p.ttt.ii. I. Cn,ry. Pltlsiol 755:753 761. Rüss.ll, c 1., J.P Mrers. a.d c i McEhan. M.R. 1938 Aconp..ison ot the retnra ofmoijnyrids u'ith thatof varnius orh€r tel€osrs. (Momyidae) / Cd,f. /'r,'/ii :127 r4.ra z.ol (sbkh.) 19: 465. Schlu8er, J H. ,nd C.D. Hopkins Mccr.go., PK and C.WM. Westb} 1992. Discimination ol in.livi.tually .hü..re.isti. ele.hic f('lld{ing clcctric c!trenl line orEan dis.hargcs blr . weakly eleckic fish.,4,rnr. ts.r.l rl3: 977 986. S.hn.d.r, H. 1967. Ivlorphology i Mcleman. D.A. a nd M J. Rynn. I 997 Responses to conspc. ific i n d h eterospecific ol factory cues lishes. In: M",,t 6d,4.0!nr in the swordtail X,plDplo,6 A,ttzi Aühü. B.lnr 54: t977-t0a3. PP 135 158 M.ycr, J.H. 1982. B€havioral respons.s of weatly elect.ic lish to complex impcdän.es / Cort Sclruster, 5 1986. Unt.6ü.hrngen, Plr rnl. A 145: .159 -170 Relonri ..). Zdit. B.irr: 29 2 Meyer, J.tl. ind C.C. BeU. 1983. S€nsory gäting by i corcllary discharSe mechanisn /. Co,,l,. Schustcr S.2000. Chan8es in thee Plryrid. A 151:,101-406. ol Cv tahß.nnpr.I. Ett Br Moller, P 1995. E/rti. Fßr.s. ilis.d'V d,n B.tfu,i',. Chapman & Hall, London. Schuster S.2001 Count anrl sparl Moller, P 2002. Multimodal senso.! int.gratnrn in rveaklt, elecbic fish: A behavnrral account /. f.turan to ser i€s of Puhcs. /. I P/,!sid. (Paris) 96: 547 556. Sch uster, S. 2002. Bchav iora I eviden Mollea P and lt. Barcr. 1973 Communication in w.akly elc.t.i. fish. C,ntha ?ü ß pctcßii sysrcm of cr/, iorrs trrrf0. / (Momv.idae) ll.lnt öctbn olelectdc orgän.tischarg. actilities of two fish.,4trn, B.r,r S.hrsrcr, S. and s. Amrsfeld. 2002. 2l: 501 512. in the (€akly electic fnh Cr Mollc., P, J. Serrier, A. Sqüirc and M. tsoudinot 1982. Social spacing 1n rhc nornyid lish ftüdanorc, R E. and llK. M.Cro8( Cnatrd,.,rrs pr'id,rti: A multis€nsory.pproach. Är,r. 8e,rß.1 30: 641 n50. arc aff{ted bt Pl,ybrck stim Moller, P, J. S€rri.r P B€lbenoitand S. tüsh 1979. Not.s on and ecolo8y oi the Swashi shi.h, K.-T, W. lvilson, M. Win: rivd mormydds {Lake K.inji, Nigena). 8.rda E.oi So.idridl. 4: 357 368 on€nlation in €lectic fish: A Montgomery j.C., F Mac.lonald, C. F. Baker and A.c. Carton. 2002. Hydrodynahic contibutions r99: 2383 2393. to mlltimodal guidance ot prey.rpture behavior in fish. BrQt? Bdraa E,oi. 59: 190-198 shohet, A.J. and PJ watt.200l r( Mo6e, PM. and H. Feshbach.1953. Metlnds oJTh.Dftti.nl Prysi.s. M.craw Hill, New York. ,4Lppy, t\n.ilin rcti.nlntr. Btltrl Myrbei8, A.A. r98r. Sound communication and int.rccption in lish€s. Ir: H.,rtr,q n,/ Sox,.l smith, RJ F. 1992. Al.in siSnals ir Cd,, r,i.0rt n t, fßrus, w'N. Tavolga, A.N. Popper and R.R. Fav (eds.) SpringeFveila8 Sqrir, A. änd P Moller 1982. EIr New York, pp.39 25. weak el€ctric lish. 8,dro,'!n Neh', J.C. 2002. Multinodal inteSiätion in the feeding b€haviors .f pr.d.rrory releost fishes. Srabeli. O B 1992. Ollactory.ontr. Bnilt Btltal Eul 59:177 1a9. T.J. HaF (ed.). Chrpman & t Northcull, RG. antt M E rüllimann. 1988. The visuäl systcn ol teleost fishes: norpholo8ical Stipctic, E.1939. Llber das Gehöro patterns and kcnds. rn So$tlt Btnag! of Aqmt n Ani,rals, J. Atema, R.R. Fat A.N. lopper, Suthcrs, l{.,^. 1966. Optomolor res and WN. Tarolga (e.ts.). Springer-Verlag. New Yorl. pp. 515-s52. lrinHrrll('r ,rltr. rl,.lrosr!!. i|it, Oirrr Sürsrs S{ll

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