Cheng Fu, Zhen-Dong Cao and Shi-Jian Fu*

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1 31 The Journl of Experimentl Biology 21, Pulished y The Compny of Biologists Ltd doi:1.122/je.82 RESERCH RTICLE The effects of cudl fin loss nd regenertion on the swimming performnce of three cyprinid fish species with different swimming cpcities Cheng Fu, Zhen-Dong Co nd Shi-Jin Fu Lortory of Evolutionry Physiology nd Behviour, Chongqing Key Lortory of niml Biology, Chongqing Norml University, Chongqing, Chin uthor for correspondence (shijinfu9@hotmil.com) SUMMRY In nture, the cudl fins of fish species re frequently lost to some extent y ggressive ehviour, predtion nd diseses. To test whether the swimming performnce of fish with different swimming cpcities would e differentilly ffected due to cudl fin loss nd regenertion, we investigted the criticl swimming speed (U crit ), swimming metolic rte (M O2 ), til et frequency (f TB ) nd til et mplitude ( TB ) fter cudl fin loss nd regenertion (2 dys) in juveniles of three cyprinid fish species: the qingo (Spinirus sinensis; strong swimmer), the common crp (Cyprinus crpio; intermedite swimmer) nd the goldfish (Crssius urtus; poor swimmer). The U crit vlues of the cudl-fin-lost qingo, common crp nd goldfish were 9, 32 nd 3% significntly lower thn those of the control groups, respectively. The mximum til et mplitude ( TBmx ) (ll three fishes), the mximum til et frequency (f TBmx ) (only the common crp nd the goldfish) nd/or the ctive metolic rte (M O2ctive ) (only the common crp) of the cudl-fin-lost fish were significntly higher thn those of the control groups. fter 2 dys of recovery, the cudl fins recovered to 1, nd 2% of those of the control groups for the qingo, the common crp nd the goldfish, respectively. However, the U crit vlues of the fin-regenerted qingo, common crp nd goldfish recovered to 8, 91 nd 9% of those of the control group, respectively. The cudl-fin-regenerted qingo nd common crp showed significntly higher TBmx nd f TBmx, respectively, compred with those of the control groups. The qingo hd higher f TBmx ut lower TBmx thn the common crp nd the goldfish, which suggested tht strong swimmer my mintin swimming speed primrily y mintining greter f TBmx, for which the cudl fin plys more importnt role during swimming, thn poor swimmer. The M O2ctive of fish (common crp) with redundnt respirtory cpcity could increse due to cudl fin loss to meet the increse in energy expenditure required y n increse in f TBmx. In ddition, the sustined swimming performnce my not e the only selective pressure cting on cudl fin size in these three species, nd the present cudl fin size my e trde-off etween sustin swimming performnce nd other fctors (e.g. sexul selection, escpe responses). Supplementry mteril ville online t Key words: ehviour, compenstion, criticl swimming speed, metolic rte, morphology, til et frequency. Received 1 Decemer 212; ccepted 28 pril 213 INTRODUCTION Swimming performnce is importnt for fish ecuse it is closely relted to the ility to gin food, to void predtors nd to perform other dily ctivities (Plut, 21; Zeng et l., 29; Kieffer, 21; Fu et l., 212). s n importnt locomotive orgn for most fish species, the cudl fin plys crucil role in propelling nd guiding fish during swimming (Luder, 2; Motni, 22; Hndegrd et l., 29). The shpe, size nd stiffness of the cudl fin re ll expected to strongly ffect swimming performnce (Plut, 2). In nture, the cudl fin is frequently oserved to e prtly lost due to ggressive ehviour, predtion nd diseses (Winemiller, 199; Ziskowski et l., 28; Sinclir et l., 211). Thus, fish must physiologiclly nd ehviourlly djust to the prole negtive effects on swimming performnce cused y cudl fin loss nd void the decline of Drwinin fitness. The reltionship etween the cudl fin nd swimming performnce hs ttrcted rod ttention for long time, nd cudl fin mputtion hs een widely used in previous studies (We, 193; We, 19; Chmpgne et l., 28; Yng et l., 213). It hs een found tht cudl fin mputtion profoundly lters the swimming ehviour nd/or speed in sockeye slmon (Oncorhynchus nerk) (We, 193), rinow trout (Slmo girdneri) (We, 19) nd Chinese rem (Prrmis pekinensis) (Yng et l., 213), while it showed no effect on swimming performnce of rown drters (Etheostom edwini) (Chmpgne et l., 28). Thus, the cudl fin my e different size nd present different level of importnce for fish with different swimming cpcities; therefore, the regenertion of the cudl fin in these fish my e different to meet those different swimming-cpcity needs. The overll chnge in swimming cpcity during cudl fin loss nd regenertion hs ecome n importnt question, ut little investigtion into this issue hs een reported. Under sustinle speeds, most fish species tht utilise ody nd cudl fin propulsion increse their swimming speed primrily y incresing their til et frequency (f TB ) nd/or their til et mplitude ( TB ) (Hunter nd Zweifel, 191; Hunter, 192; Dickson et l., 22). Vrition in f TB nd TB could therefore e used s n indictor of mechnicl power output (Ellery, 21). When fish with cudl fin loss or prtil cudl fin regenertion swim t the sme speed s fish with intct cudl fins, f TB nd/or TB my increse due to the decresed effective re for thrust, to generte similr thrust to tht

2 31 The Journl of Experimentl Biology 21 (1) Fig. 1. Photogrphs of the left side of intct, cudl-fin-lost nd prtly regenerted fish (qingo, common crp nd goldfish). of fish with intct cudl fins, which my increse the energy expenditure of fin-dmged fish when swimming t given speed (Plut, 2). Thus, cudl fin dmge my result in decline in swimming performnce. However, the decresed cudl fin re will lso result in decrese in drg during swimming (We, 193; Sinclir et l., 211), mking it esier for fish with dmged cudl fins to finish ech til et. In ddition, fin shpe nd size in mny fish species is suject to sexul selection, either ecuse femles choose to mte with mles tht hve lrger fins or ecuse mles with lrger fins gin ccess to more femles through mle-to-mle competition (Wrner nd Schultz, 1992; Jordn et l., 2; Wilson et l., 21). Thus, for mny fish species, the existing size of the cudl fin my not e est suited to sustinle swimming performnce, ut insted my e response to sexul selection or compromise with unstedy swimming performnce, which come from the selective pressure of reproduction nd escpe, respectively (Sinclir et l., 211). If tht is the cse, it will e interesting to investigte the chnges in swimming cpcity for cudl-fin-dmged fish, especilly chnges in f TB, TB nd the metolic rte (M O2 ) during swimming. In ddition, chnges in f TB, TB nd M O2 during swimming cused y decresed fin re my e different in fish with different swimming cpcities nd different cudl fin shpes nd sizes. The mximum sustinle swimming speed, or criticl swimming speed (U crit ), hs long een widely used prmeter for the evlution of eroic swimming ility (Plut, 21; McNutt et l., 2; Li et l., 21). The mximum oxygen consumption (ctive oxygen consumption rte, M O2ctive ) during the U crit test ws ssumed to e the mximum eroic metolic cpcity (lsop nd Wood, 199; Lee et l., 23; Fu et l., 211). However, recent studies found tht the locomotion ctivity lone cnnot elicit the mximum metolic rte in fish species such s the common crp (Dupont-Prinet et l., 29; Png et l., 211; Zhng et l., 212). Thus, for those fishes, the high respirtory cpcity my llow greter increse in f TB nd TB fter fin loss. Thus, we hypothesise tht fish with different swimming nd respirtory cpcities my hve different chnges in swimming cpcity, swimming ehviour (f TB nd TB ) nd metolic rtes due to cudl fin loss nd regenertion. To test our hypothesis, we selected three Cyprinide fish species: the qingo [Spinirus sinensis (Bleeker 181)], the common crp (Cyprinus crpio Linneus 18) nd the goldfish [Crssius urtus (Linneus 18)] (Fig. 1, Tle 1). The qingo shows superior swimming performnce nd hs the smllest cudl fin (Tle 1) (Zhng et l., 212). The goldfish is poor swimmer ut with lrge, long cudl fin. The swimming cpcity nd cudl fin size of the common crp is moderte, nd it hs redundnt respirtory cpcity tht is greter thn necessry for locomotion (Png et l., 211; Zhng et l., 212). These three cyprinid species re ll ctive, omnivorous fishes, nd they hve close phylogenetic reltionship to the Brine sufmily (Kong et l., 2). Thus, ny possile noise from genetic nd ecologicl fctors during sttisticl nlysis ws minimised in the present study. We first mesured the chnge in swimming performnce fter cudl fin loss in the qingo, the common crp nd the goldfish. Then, following 2 dys of recovery, we repeted the mesurement of swimming performnce. The ims of this study were (1) to test whether cudl fin loss nd regenertion hd different effects on swimming performnce mong fishes with different swimming cpcities, nd (2) to test whether the fish could compenste for cudl fin loss Tle 1. Body mss, ody length nd ody nd cudl fin morphology in juvenile qingo, common crp nd goldfish Group N Body mss (g) Body length (cm) Fitness rtio Cudl fin index (%) Cudl fin spect rtio (%) Qingo dys 1.32±.2.21±.12 3.±. 3.3±.1 3.±.9 1.3±.32.2±.1 3.±. 2 dys 1.9±..8±.1 3.±.2 3.± ±.1 2 dys Recovery 1.±.33.3±.11 3.±.2 1.±. 2.±.12 Common crp dys 1 8.±.3.8±.1 3.±..2± ± ±.21.8±. 3.±.3 2 dys ±.32.8±.9 3.1±..1± ±.9 2 dys Recovery 1 8.9±.3.99±.13 3.± ± ±.1 Goldfish dys 8 9.3±.3.8±.11 2.±.2 1.2± ± ±.29.3±.1 2.±. 2 dys 8 9.±.3.±. 2.9±.3 1.1± ±.1 2 dys Recovery 1 9.1±.2.3±. 2.3±.2 3.±.2 2.9±.1

3 Fin nd swimming performnce 31 through kinemtics (f TB nd TB ) nd whether these compenstions were relted to swimming cpcity nd cudl fin size. MTERILS ND METHODS Experimentl nimls nd holding Experimentl juvenile qingo ( 11 g, N=1), common crp ( 12 g, N=1) nd goldfish ( 13 g, N=1) were otined from locl frmers nd kept in dechlorinted tnks for 1 month efore the experiments were performed (Tle 1). ll of the fish were kept in the sme type of tnks (length width height, 1... m) nd ssessed over the sme seson nd time frme. The fish were fed to stition with commercil diet once dily t 9: h. The uneten food nd feces were clered using siphon 1 h fter feeding. The wter temperture ws mintined t 2.±. C, nd the wter oxygen content ws mintined ove. mg l 1. The mmoni-n rnged from. to.2 mg l 1. Fish were mintined on 12 h:12 h light:drk photoperiod cycle. We declre tht the experiments comply with the current lws of the country in which the experiments were performed. Experimentl protocol ll tests were performed t wter temperture of 2 C. t the eginning of the experiment, 2 fish of ech fish species (18 fish for goldfish) were chosen from the holding tnks nd rndomly divided into two groups, i.e. hlf of the fish were plced into the control groups (with no tretment to the cudl fin) nd the other hlf were plced into the cudl fin tretment groups (cudl fin mputtion). For fish in the tretment groups, ech individul fish ws trnsferred to ucket with 2 l of clen nd dechlorinted wter nd ws nesthetised with eugenol (3 mg l 1 ) (Velíšek et l., 2). Then, oth the epxil nd hypxil cudl fin loes of the fish in the tretment groups were mputted with pir of shrp scissors, ~2 mm from the til musculr peduncle (We, 193). fter mputtion, the fish were returned ck to the holding tnks nd llowed 8 h recovery period efore ny experimentl mesurement. No fish died during the whole mnipultion process. pilot experiment reveled tht the nesthesi hd no significnt effects on swimming locomotion fter 8 h of recovery (supplementry mteril Figs S1, S2, Tle S1). The fish in the control group remined in the holding tnks. fter 8 h, the swimming performnce of fish in oth the control nd tretment groups ws mesured. During the 8 h, the fish of oth control nd tretment groups were kept unfed. The fish were individully introduced into Brett-type swimming tunnel respirometer (Brett, 19) nd held for 1 h t slow wter velocity (~3 cm s 1 ) for recovery (Jin et l., 199). First, we conducted pilot experiment to determined the pproximte U crit nd found tht there ws no significnt difference in U crit mesured y different initil swimming speed (supplementry mteril Figs S3, S, Tle S1). Then the individul fish were tested in rmp-u crit test for the mesurement of U crit nd M O2 during swimming. The rmp-u crit tests involved incresing wter speed to ~% of U crit over min period, fter which wter speed ws incresed y cm s 1 increments every 2 min until the fish ecme exhusted. Simultneously, the swimming ehviour of ech individul fish ws recorded using digitl cmer in video mode (model IXUS 1, Cnon, Tokyo, Jpn; 3 frmes s 1 ) positioned ove the respirometer to otin dorsl view of the fish during ech swimming speed. The videos were used for the mesurement of f TB nd TB. fter the U crit test, the fish were individully nesthetised with eugenol (3 mg l 1 ) (Velíšek et l., 2) to mesure ody mss nd length, nd then photogrphs of the right side of ech individul fish were tken for morphometric mesurements of the ody nd the cudl fin. The strting swimming speeds of cudl-fin-lost fish during the U crit test mong the three different species were different from those of cudl-fin-intct fish; thus, oth fin-lost nd fin-intct fish swm for similr durtion in the U crit test (Fig. 3). ll the fish were then trnsferred to their previous tnks nd llowed to recover for 2 dys, i.e. the tretment of 2 dys recovery; the tretment of fin-loss is referred to s dys for comprison. The housing conditions for this recovery period were the sme s those in the holding period. Following recovery, the mesurements of U crit, M O2, f TB nd TB of the fish of oth tretment nd control groups were repeted, following the sme procedures s the first time. Prmeter mesurements Mesurement of U crit nd swimming M O2 Brett-type swimming tunnel respirometer (Brett, 19) ws used to mesure U crit nd M O2 during swimming s function of swimming speed (for detils, see Png et l., 21). The respirometer ws constructed from cler plstic poly-methyl-methcrylte. circulting wter flow ws generted in the tunnel (totl volume 3. l) y n crylic propeller ttched to vrile speed pump. The speed pump ws controlled y vrile voltge power source. digitl cmer in video mode ws used to clirte the wter velocity from the pump controller y trcking smll lck gr lls (with density the sme s wter) in current. Then the reltionship etween wter velocity nd voltge output could e uilt to n indicil eqution. The wter velocity could e chieved y tuning the voltge output. honeycom screen ws secured t oth ends of the swimming chmer to reduce turulence nd to ensure uniform wter velocity cross the swimming chmer. Ech individul fish ws plced downstrem of the propeller in swimming chmer with 19.9 cm 2 cross-sectionl re. The wter temperture in the swimming chmer ws controlled to within ±.2 C using wter th connected to stinless steel het exchnger. U crit ws clculted for ech individul fish using Brett s eqution (Brett, 19): U crit = V + (t / T) ΔV, (1) where V is the highest speed t which the fish swm during the full time period of the experiment (cm s 1 ); ΔV is the velocity increment [pproximtely 1 ody length (BL) s 1 ; cm s 1 ]; T is the prescried period of swimming per speed (2 min); nd t is the time tht the fish swm t the finl speed (min). The criterion for determining whether n individul fish filed to swim ws when the fish filed to move off the rer honeycom screen of the swimming chmer for 2 s (Lee et l., 23). The O 2 concentrtion ws mesured continuously throughout the rmp-u crit test s function of swimming speed. The respirometer could switch etween n open mode nd closed mode to replenish the oxygen nd to mesure the M O2, respectively. In the open mode (~2 min), the respirometer ws supplied with fully erted nd thermo-regulted wter. In the closed mode (2 min), the tunnel ws isolted from the reservoir tnk nd the wter ws recirculted within the system. smll volume of wter ws drwn from the seled respirometer y smll pump, forced pst dissolved oxygen proe housed in seled temperture-controlled chmer ( ml), nd then returned to the respirometer. The oxygen concentrtion (mg l 1 ) ws recorded once every 2 min. The M O2 (mg kg 1 h 1 ) of ech individul fish during swimming ws clculted from the depletion of oxygen, ccording to the eqution: M O2 = Sv / m, (2) where S (mg l 1 min 1 ) is the decrese in the wter s dissolved oxygen content per minute (slope); v is the totl volume of the respirometer

4 31 The Journl of Experimentl Biology 21 (1) (3. l) minus the volume of the fish; nd m is the ody mss (kg) of the fish. The slope ws otined from liner regression etween time (min) nd the dissolved oxygen content (mg l 1 ). Only slopes with n r 2 >.9 were considered in the nlysis. The mximum M O2 during the U crit test ws defined s the ctive M O2 (M O2ctive ). The wter oxygen content in the respirometer ws never llowed to fll elow 8% oxygen sturtion y switching etween the open nd closed mode of the respirometer (Clireux et l., 2). Mesurement of f TB nd TB during swimming 1-min video recording ws mde t ech speed t which fish swm during its M O2 mesurements. 1 cm ruler of similr height to the fish swimming in the chmer ws used to clculte scling fctor from ech video. The f TB ws clculted from the two-dimensionl disply of the progression of the tip of the til over time y dividing the numer of consecutive til et cycles y the time. Ech 2-min video recording (when the fish ws positioned in the centre of the chmer nd swm stedily) tht ws selected from the former 1-min recording for ech swimming speed of ech individul fish ws used to count the numer of til ets, which ws then trnsformed into til ets per minute. One til et cycle ws defined s the excursion of the til from one side of the ody to the other nd ck gin. Using the sme twodimensionl disply, the TB, the distnce etween the lterl-most positions of the tip of the cudl peduncle during one complete til et cycle nd the middle xis of the ody, ws clculted y mesuring the distnce of ech symmetricl til et in pixels. These vlues were then converted into centimetres y dividing y the scling fctor (pixels cm 1 ) clculted prior to digitising. Video segments in which the fish ws swimming stedily for eight til ets nd ws positioned in the centre of the chmer, wy from the wlls nd the ottom of the chmer, were selected for TB nlysis. Five points long the dorsl midline of ech fish tht could e identified consistently were digitised in sequentil video fields for eight til ets t ech speed: the tip of the snout, the points long the dorsl midline etween oth the nterior nd the posterior insertion points of the eyes, the midpoint etween the nterior insertions of the pectorl fins, nd the tip of cudl peduncle (Donley nd Dickson, 2). The TB (cm) ws trnsformed into percentge of the fish ody length (%BL) to reduce the influence of ody length (Donley nd Dickson, 2; Dickson et l., 22). Mesurement of morphology Geometric morphometric methods were used to quntify the ody nd cudl fin shpes. Photogrphs of the right side of ech fish, viewed together with ruler, were tken with digitl cmer nd then nlysed with tps softwre ( We mesured ody length, ody height, cudl fin re nd cudl fin height, nd clculted the vlues of the following morphologicl trits: (1) fitness rtio (FR)=ody length/ody height; (2) cudl fin spect rtio (R)=cudl fin height 2 /cudl fin re; nd (3) cudl fin index (FI)=cudl fin re/ody length 2. Dt hndling nd nlysis Sttistics1 (SPSS, Chicgo, IL, US) ws used for dt nlysis. ll vlues re presented s mens ± s.e.m., nd P<. ws used s the level of sttisticl significnce. The effects of species, cudl fin tretment nd recovery period on U crit, M O2ctive, f TBmx nd TBmx were determined using mixed-model three-wy NOV in three fish species. The effects of swimming speed nd cudl fin tretment on swimming M O2, f TB nd TB were determined using one-wy nlysis of covrince (NCOV), i.e. we performed regression for ech tretment group nd then mde comprison of their coefficients. The NOV ws followed y Duncn test or t-test if it ws necessry to determine the difference of the vlue of different tretment groups. t-test ws used to determine the difference etween the control nd the tretment groups. RESULTS Effects of cudl fin loss nd regenertion on U crit Species effect Species hd significnt effects on U crit (F 2,2 =2.2, P<.1; Fig. 2, Tle 2). The U crit of goldfish ws significntly lower thn tht of common crp while the ltter ws significntly lower thn tht of the qingo in oth the control nd recovery groups (P<.). Ucrit (cm s 1 ) 3 2 1, Fin tretment c # # c c # Fig. 2. Criticl swimming speed (U crit ) () nd ctive metolic rte (M O 2ctive) (B) of control (open rs) nd tretment (filled rs; cudlfin-lost fish t dys nd cudl-fin-regenerted fish t 2 dys recovery) groups of juvenile qingo, common crp nd goldfish. Different lowercse letters indicte sttisticlly significnt differences etween fish species in oth control nd tretment groups. Significnt difference in vriles etween control nd tretment groups. # Significnt difference in vriles etween dys nd 2 dys (recovery) groups (P<.). Dt re mens ± s.e.m. M O2ctive (mg O2 kg 1 h 1 ) B Qingo Common Goldfish Qingo Common Goldfish crp crp dys 2 dys recovery

5 Fin nd swimming performnce 318 Tle 2. The effect of species (etween-suject fctor), cudl fin mputtion (etween-suject fctor) nd 2 dys recovery (withinsuject fctor) on swimming prmeters, sed on mixed-model three-wy NOV Species effect (S) 2 F=2.2 P<.1 Tretment effect (T) 1 F=3.8 P<.1 Recovery effect (R) 1 F=2.9 P<.1 S T 2 F=23.8 P<.1 S R 2 F=9.3 P<.1 T R 1 F=19.2 P<.1 S T R 2 F=3.9 P=.29 Significntly different (P<.). d.f. U crit M O2ctive f TBmx TBmx F=3.23 P<.1 F=. P=.99 F=. P=.99 F=.98 P=.391 F=.222 P=.8 F=3.21 P=.9 F=. P=.3 F=1.8 P<.1 F=.3 P=.82 F=1.9 P<.1 F=.12 P=.1 F=1.2 P<.1 F=2. P=.123 F=1.8 P=.19 F=12.2 P<.1 F=2.19 P<.1 F=3.13 P<.1 F=.13 P=.883 F=.9 P=.398 F=3.89 P<.1 F=3.82 P=.29 Tretment effect Cudl fin tretment lso hd significnt effects on U crit (cudl fin loss, F 1,2 =3.8, P<.1; Fig. 2, Tle 2). The qingo, the common crp nd the goldfish showed significntly different 9, 32 nd 3% decrese in U crit, respectively, following cudl fin loss (interction effect: F 2,2 =23.8, P<.1). Recovery effect fter 2 dys of recovery, the cudl fin index of cudl-finregenerted fish recovered to 1, nd 2% of those of the control group for the qingo, the common crp nd the goldfish, respectively (Fig. 1, Tle 1). The U crit of the cudl-finregenerted qingo, common crp nd goldfish ws significntly incresed (F 1,2 =2.9, P<.1) nd recovered to 8, 91 nd 9% of those of the control group, respectively (interction effect: F 1,2 =19.2, P<.1), nd there ws no significnt difference in U crit etween goldfish in the cudl-fin-regenerted nd the control group (P=.1). Effects of cudl fin loss nd regenertion on M O2 during swimming mong fish in the dys groups, M O2 incresed significntly with n increse in the swimming speed for ll experimentl groups (P<.1), ut it incresed more shrply in the tretment groups for ll three fish species compred with those of the control groups within ech species (P<.; Fig. 3,C,E, Tle 3). fter 2 dys of recovery, there ws no significnt difference etween the M O2 speed curves of the cudl-fin-regenerted nd the control groups in ll three species (Fig. 3B,D,F). Effects of cudl fin loss nd regenertion on M O2ctive Species effect Species hd significnt effect on M O2ctive (F 2,2 =3.23, P<.1; Fig. 2B, Tle 2). The M O2ctive vlues of the qingo were significntly higher thn those of the common crp nd the goldfish in oth the control nd the recovery groups (P<.; Fig. 2B). Tretment effect Tretment hd no effect on M O2ctive (F 1,2 =., P=.99; Fig.2B, Tle 2). However, the M O2ctive of the common crp incresed significntly fter cudl fin loss in the control group y t-test (P=.2). Recovery effect Recovery hd no effect on M O2ctive (F 1,2 =., P=.99; Fig. 2B, Tle 2). Effects of cudl fin loss nd regenertion on f TB during swimming The f TB incresed significntly with n increse in the swimming speed for ll experimentl groups, ut it incresed more shrply in the tretment groups for ll three fish species compred with those of the control group within ech species (P<.; Tle 3, Fig., Fig., Fig. ). fter 2 dys of recovery, only cudl-finregenerted goldfish showed shrper curve compred with those of the control group (Fig. C, Fig. C, Fig. C). Effects of cudl fin loss nd regenertion on f TBmx Species effect Species hd significnt effects on f TBmx (F 2,2 =1.8, P<.1; Fig., Tle2). The f TBmx vlues of the qingo were significntly higher thn those of oth the common crp nd the goldfish in oth the control nd recovery groups (P<.1). Tretment effect The f TBmx of the common crp (P=.1) nd the goldfish (P=.13) incresed significntly y 13 nd 11%, respectively, fter cudl fin loss, while there ws no significnt difference in the qingo (interction effect: F 1,2 =.12, P<.1). Recovery effect fter 2 dys of recovery, the f TBmx of common crp decresed significntly (P<.1). Thus, there ws no significnt difference etween cudl-fin-regenerted nd control groups in the common crp (P=.3) while the cudl-fin-regenerted goldfish still showed significntly higher f TBmx thn tht of the control fish (P=.1; Fig. ). Effects of cudl fin loss nd regenertion on TB during swimming The TB incresed significntly with incresed swimming speeds for ll experimentl groups, ut it incresed more shrply in the tretment groups in ll three fish species compred with those of the control group within ech species (P<.1; Tle 3, Fig. B, Fig. B, Fig. B). There ws no significnt difference in slope of

6 319 The Journl of Experimentl Biology 21 (1) dys 2 dys recovery Fig. 3. Oxygen consumption B rte of control (cudl-finintct fish; filled circles) nd F: y=(.±.)x+(.298±.81) 8 F: y=(.31±.1)x+(.32±.) Fin regenertion N=3, R 2 =.88, P<.1. N=, R 2 =.89, P<.1 tretment (open circles; cudl-fin-lost fish t dys. nd cudl-fin-regenerted fish t 2 dys recovery) groups of qingo (,B),. C: y=(.3±.2)x+(.28±.8) common crp (C,D) nd C: y=(.3±.1)x+(.33±.) N=, R 2 =.81, P<.1 goldfish (E,F). N=8, R 2 =.82, P<.1. ln (M O2) (mg O2 kg 1 h 1 ) C 8 F : y=(.±.3)x+(.388±.33). N=, R 2 =.1, P<.1.. C: y=(.2±.2)x+(.±.1) N=9, R 2 =.8, P<.1. 8 D F: y=(.33±.3)x+(.133±.1). N=2, R 2 =., P<.1... C: y=(.32±.2)x+(.18±.) N=, R 2 =.92, P< E F: y=(.±.)x+(.399±.89) N=8, R 2 =.9, P<.1 C: y=(.31±.2)x+(.1±.) N=2, R 2 =.831, P< F F: y=(.3±.2)x+(.3±.) N=, R 2 =.82, P<.1 C: y=(.38±.2)x+(.233±.8) N=2, R 2 =.91, P<.1 Swimming speed (cm s 1 ) TB swimming speed curve etween control nd fin-regenerted fish. However, oth qingo nd common crp still showed significntly higher TB thn those of the control groups due to the significntly higher intercept (P<.), while there ws no significnt difference etween the cudl-fin-regenerted nd control groups in goldfish. Effects of cudl fin loss nd regenertion on TBmx Species effect Species hd significnt effects on TBmx (F 2,2 =12.2, P<.1; Fig. B, Tle 2). The TBmx of the qingo ws significntly lower thn those of the common crp nd the goldfish in oth the control nd recovery groups (P<.1). Tretment effect Cudl fin tretment hd significnt effects on the TBmx (F 1,2 =2.19, P<.1; Fig. B, Tle 2). mong the control groups, the TBmx vlues of the qingo, the common crp nd the goldfish incresed significntly y 1, 2 nd 1%, respectively, fter cudl fin loss (P<.1). Recovery effect fter 2 dys of recovery, the TBmx of ll three fish species decresed significntly (F 1,2 =3.13, P<.1; Fig. B, Tle 2). Only cudl-fin-regenerted qingo showed significntly higher TBmx thn the control groups (P=.11; Fig. B) while the TBmx of oth the cudl-fin-regenerted common crp (P=.9) nd the cudl-fin-regenerted goldfish (P=.91) did not chnge compred with those of the control groups. DISCUSSION The present study imed to investigte the effects of cudl fin loss nd regenertion on swimming locomotive performnce in juveniles of three cyprinid fish with different swimming cpcities, morphologies nd metolic cpcities. We found tht cudl fin loss hd pronounced negtive effects on swimming performnce, ut the effects were different mong different fish species. To cope with the decline in the effective re for thrust following cudl fin loss, ll three fish species showed significnt increses in TBmx, f TBmx nd/or M O2ctive. fter 2 dys of recovery, the cudl fins of the fish in the tretment groups recovered to pproximtely 2 % while U crit vlues recovered to 8 9%. We found tht strong swimmer my mintin swimming speed primrily y mintining greter f TBmx nd smller TBmx, for which the cudl fin plys more importnt role during swimming thn for poor swimmer. nother interesting finding ws the symmetry of recovery etween cudl fin nd swimming performnce, which suggested tht these three fish species my not hve the est equipped cudl fin size

7 Fin nd swimming performnce 31 Tle 3. The difference in vrile swimming speed curves etween control nd fin-loss (or fin-regenertion) groups within ech fish species ccording to the results of one-wy NCOV Qingo Common crp Goldfish dys 2 dys dys 2 dys dys 2 dys d.f. 1, 12 1, 1 1, 12 1, 19 1, 9 1, 91 M O2 Intercept F=.23 P=.33 F=. P=.98 F=.8 P=.12 F=.1 P=.9 F=.18 P=.893 F=. P=.2 Slope F=1.9 P<.1 F=.3 P=.1 F=28.98 P<.1 F=.89 P=. F=9. P=.3 F=1. P=.33 f TB Intercept F=1.28 P=.2 F=.2 P=.8 F=.8 P=.12 F=.2 P=. F=1.83 P=.1 F=2.13 P=.1 Slope F=82.8 P<.1 F=1.22 P=.2 F=3. P<.1 F=3.9 P=. F=11.99 P=.1 F=.81 P=.18 TB Intercept F=28.2 P<.1 F=3.9 P<.1 F=3.8 P<.1 F=9.33 P=.3 F=18.3 P<.1 F=2. P=.1 Slope F=.2 P<.1 F=.1 P=.9 F=1.1 P<.1 F=.2 P=.8 F=19.11 P<.1 F=.3 P=.81 See Figs 3 for the regression equtions, nd hence the intercept nd slope coefficient vlues of ech fish group. needed to sustin swimming performnce, nd some other fctors (e.g. sexul selection, escpe responses) my lso e involved in the size nd shpe of the cudl fin. f TB nd TB s function of swimming performnce Swimming locomotive performnce hs ttrcted much ttention for long time ecuse of its importnce for survivl (Plut, 21; Zeng et l., 29; Kieffer, 21). It is generlly elieved tht the ody morphology necessry to mximise stedy swimming efficiency involves stremlined ody shpe nd high R (Fisher nd Hogn, 2; Lngerhns, 29). There my e morphologicl reson tht the U crit of the qingo is higher thn tht of the common crp nd the goldfish; nd while the lrge, long cudl fin of the goldfish is less stiff nd hs higher drg, it hd the lowest U crit of the three fish species, though it hd high R. t sustinle swimming speeds, most fishes utilise ody nd cudl fin propulsion to drive them forwrd. The incresed propulsion, long with swimming speed, is governed y n increse in f TB nd TB (nderson nd Johnston, 1992; Ellery, 21). Binridge (Binridge, 198) nd Hunter nd Zweifel (Hunter nd Zweifel, 191) showed tht speed during stedy swimming is determined y f TB nd tht TB is essentilly constnt when f TB is greter thn Hz (Fuimn nd Btty, 199); in contrst, previous studies showed tht the chu mckerel (Scomer jponicus) (Gi et l., 1999; Donley nd Dickson, 2) nd cod (Gdus morhu) (Weer et l., 21) incresed their TB with swimming speeds during the entire swimming process (including when f TB ws greter thn Hz). In the present study, oth f TB nd TB in ll three fish species showed significnt increses with n increse in swimming speed during the entire swimming process. There is ftb (no. min 1 ) F: y=(12.12±.)x+(28.9±11.1) C N=, R 2 =.913, P<.1 F: y=(.8±.31)x+(2.81±12.3) N=, R 2 =.8, P<.1 dys dys C: y=(.392±.283)x+(228.39±11.) 2 dys recovery N=3, R 2 =.88, P<.1 Fin regenertion C: y=(.898±.3)x+(29.9±1.93) N=, R 2 =.82, P<.1 TB (%BL) B D Swimming speed (cm s 1 ) F: y=(.3±.28)x+(.82±.3) N=3, R 2 =., P<.1 F: y=(.23±.1)x+(8.28±.11) N=8, R 2 =.8, P<.1 2 dys recovery C: y=(.1±.8)x+(.±.319) N=3, R 2 =.8, P<.1 Fin regenertion C: y=(.238±.13)x+(.3±.) N=, R 2 =.81, P<.1 Fig.. Til et frequency (f TB ;,C) nd til et mplitude ( TB ; B,D) of control (cudl-fin-intct fish; filled circles) nd tretment (open circles; cudl-finlost fish t dys nd cudl-fin-regenerted fish t 2 dys recovery) groups of qingo.

8 311 The Journl of Experimentl Biology 21 (1) ftb (no. min 1 ) C F: y=(11.18±.3)x+(18.39±11.2) N=1, R 2 =.8, P<.1 F: y=(.3±.399)x+(183.2±11.) N=2, R 2 =.8, P<.1 dys dys C: y=(.2±.39)x+(11.±13.1) N=, R 2 =.8, P<.1 2 dys recovery Fin regenertion C: y=(.199±.9)x+(13.19±1.32) N=1, R 2 =.8, P<.1 TB (%BL) B D Swimming speed (cm s 1 ) F: y=(.321±.28)x+(11.2±.9) N=1, R 2 =.92, P<.1 F: y=(.23±.1)x+(8.28±.11) N=8, R 2 =.8, P<.1 C: y=(.29±.13)x+(.29±.) N=2, R 2 =.8, P<.1 2 dys recovery Fin regenertion C: y=(.238±.13)x+(.3±.) N=, R 2 =.81, P<.1 Fig.. s Fig., ut for common crp. gret del of vriility in the present nd pulished dt, possily ecuse of the different species nd sizes of the fish; for instnce, lrge herring (Clupe hrengus) lrve modulted swimming speed without mking significnt chnges to their TB, ut the smll lrve vried their TB with swimming speed, despite the fct tht their f TB vlues were greter thn Hz (Fuimn nd Btty, 199). The qingo, which is strong swimmer, showed higher f TBmx ut lower TBmx thn the common crp nd the goldfish. These dt suggest tht strong swimmers my primrily rely on their higher f TBmx to chieve their greter swimming cpcity ecuse the lterlly moving portions of their ody experience n ugmented drg (Lighthill, 191). However, higher f TBmx will led to higher energy expenditure ecuse f TB hs strong, positive correltion with M O2 (Herskin nd Steffensen, 1998; Lowe, 21; Steinhusen et l., 2); thus, the strong-swimmers (qingo) hve higher M O2ctive thn the common crp nd the goldfish to stisfy the higher energy expenditure cused y higher f TBmx. The kwkw tun (Euthynnus ffinis) hd greter f TB nd lower TB thn the chu mckerel nd lso hd higher energy expenditure (Donley nd Dickson, 2). Thus, good swimmers my keep their high swimming cpcity t the cost of high energy expenditure ecuse of the importnce of swimming cpcity for those fish. The effects of cudl fin loss on the swimming performnce of three fish species The cudl fins re the min trnsmitters of momentum from the muscles to the wter. Without cudl fins, the effective re for thrust is sustntilly reduced, nd the ovious result is reduction ftb (no. min 1 ) C F: y=(11.2±1.2)x+(192.±2.) N=, R 2 =.28, P<.1 F: y=(9.±.31)x+(1.1±1.9) N=, R 2 =.91, P<.1 dys dys C: y=(.±.3)x+(19.2±13.8) N=1, R 2 =.89, P<.1 2 dys recovery Fin regenertion C: y=(8.323±.33)x+(132.89±11.1) N=1, R 2 =.92, P<.1 TB (%BL) B D Swimming speed (cm s 1 ) F: y=(.19±.3)x+(1.13±.1) N=, R 2 =.81, P<.1 F: y=(.28±.1)x+(.±.1) N=, R 2 =.82, P<.1 C: y=(.2±.1)x+(.99±.13) N=1, R 2 =.8, P<.1 2 dys recovery Fin regenertion C: y=(.291±.1)x+(.1±.3) N=38, R 2 =.913, P<.1 Fig.. s Fig., ut for goldfish.

9 Fin nd swimming performnce 312 ftbmx (no. min 1 ) 3 2 Fin tretment # Fig.. Mximum til et frequency (f TBmx ; ) nd mximum til et mplitude ( TBmx ; B) of control (open rs) nd tretment (filled rs; cudl-fin-lost fish t dys nd cudl-finregenerted fish t 2 dys recovery) groups of qingo, common crp nd goldfish. Different lowercse letters indicte sttisticlly significnt differences etween fish species in oth control nd tretment groups. Significnt difference in vriles etween control nd tretment groups. # Significnt difference in vriles etween dys nd 2 dys (recovery) groups (P<.). Dt re mens ± s.e.m. 1 TBmx (%BL) B Qingo Common crp Goldfish Qingo Common crp Goldfish dys 2 dys recovery # # # in swimming performnce (Plut, 2). The U crit of no-til or cudl-fin-lost zerfish (Dnio rerio), Chinese rem (Prrmis pekinensis) nd sockeye slmon (Oncorhynchus nerk) significntly decresed y % (1..9 BL s 1 ) (Plut, 2), % (.83. BL s 1 ) (Yng et l., 213) nd 1% ( BL s 1 ) (We, 193), respectively, compred with those of cudl-fin-intct fish. In the present study, the strong-swimming qingo lso showed the gretest decrese (9%, BL s 1 ) in U crit fter cudl fin loss mong the three selected fish species. These dt suggested tht the cudl fins of strong-swimming fish plyed more importnt role in swimming performnce thn those of poor-swimming fish. nimls often tke some mesures to compenste for decrese in locomotive cpcity ecuse of its importnce for survivl. Loded green noles took off t steeper ngles compred with unloded noles to compenste for reduction in tke-off speed cused y loding (Kuo et l., 211). Bluegill sunfish (Lepomis mcrochirus) with prtilly impired pectorl fins (3% originl fin re) protrcted their pectorl fins significntly more to compenste for decrese in decelertion ility during rking (Highm et l., 2). The cudl-fin-lost Chinese rem showed higher f TB, TB nd M O2 t higher swimming speed (Yng et l., 213). In the present study, to cope with decline in swimming cpcity s consequence of cudl fin loss, three cyprinid fish species ll showed swimming ehviourl nd metolic chnges. Like the Chinese rem, the f TB, TB nd M O2 of the cudl-fin-lost qingo, common crp nd goldfish were significntly higher thn those of intct fish within ech species t ny given swimming speed. These increses my occur ecuse the cudl-fin-lost fish require thrust similr to tht of intct fish t the sme swimming speeds. The genertion of similr thrust for cudl-fin-lost fish would require greter til et frequency, greter til et mplitude nd greter energy input ecuse proportionlly more energy is lost in cross-flows round the reltively lrger circumference (We, 193). In ddition, ll three cyprinid fish showed significnt increses in their TBmx, which might prtly compenste for the sustntil decline in propulsion cused y fin loss, to certin degree ecuse n incresed ody curvture produces lrger thrust nd greter energy output (McHenry et l., 199; zizi nd Lnderg, 22; Porter et l., 29). However, the improved TBmx of cudl-finlost fish my minly e cused y loss of drg s consequence of decresed propeller re (Binridge, 193; We, 193). Moreover, oth the common crp nd the goldfish showed significnt increses in their f TBmx, while only the common crp showed significnt increse in M O2ctive. It used to e ssumed tht the M O2ctive ws the mximum metolic rte, limited y the oxygen-sorption cpcity of the crdio-rnchil system. However, recent studies found tht, t lest for some fish species, such s the common crp nd the se ss (Dicentrrchus lrx), M O2ctive ws not the mximum metolic rte ecuse fed fish showed higher M O2ctive thn tht of fsting fish (Thorrensen nd Frrell, 2; Png et l., 211). Therefore, the common crp showed higher M O2ctive due to incresed energy expenditure s result of the swimming ehviourl compenstion in f TBmx. It is interesting tht the cudl-fin-lost goldfish lso showed significntly higher f TBmx ut n unchnged M O2ctive compred with those of intct fish. This result my e due to the lrge nd long, ut soft nd less effective, cudl fin of the goldfish. The cudl fins in the goldfish were. nd 3.1 times lrger thn those of the qingo nd the common crp, respectively. Thus, lrge-long-finned goldfish re likely to e more ffected y drg forces nd, therefore, less efficient swimmers (Plut, 2). sustntil decline in drg on the cudl-fin-lost goldfish mde it esier to complete ech til et. Thus, the cudl-fin-lost goldfish showed significnt increse in the f TBmx ut not in the M O2ctive compred with those of intct fish. Furthermore, some other resons, for exmple, the possile incresed C 2+ hndling cpcity when fcing intensified oxygen nd energy demnd during swimming fter cudl fin loss, my

10 313 The Journl of Experimentl Biology 21 (1) lso contriute to the increses in TBmx nd f TBmx, s suggested y recent study in common crp (Seecher et l., 212). The effects of cudl fin regenertion on the swimming performnce of three fish species Cudl fin loss must hve serious negtive impct on the growth nd survivl of fish (Winemiller, 199). For exmple, the dmged fins of cptive fish re more susceptile to cteril nd fungl infection (Böckelmnn et l., 21). Fin dmge dversely ffects swimming performnce, which, in turn, hinders feeding nd escpe efficiency (Sinclir et l., 211; Szim nd Poml, 1988). Therefore, fish require rpid cudl fin regenertion to decrese ll of these negtive effects. The epidermis hs fundmentl role in the regenertive process of fish fins (kimenko et l., 199; Böckelmnn et l., 21), nd this complex process strts only 12 h following loss in dult zerfish (ndresen et l., 2). Brown drters (Etheostom edwini) completely regenerted their fins during dys t 21 C (Chmpgne et l., 28). fter 2 dys of recovery for three fish species, the cudl fin index of the cudlfin-regenerted fish recovered to 1, nd 2% of the cudl-finintct fish in the qingo, the common crp nd the goldfish, respectively. The cudl fins of the goldfish regenerted the slowest of the three fish species, which my e due to the lrger cudl fin re of intct goldfish. However, it is mzing tht the U crit of the qingo, the common crp nd the goldfish (which showed no significnt differences etween cudl-regenerted nd cudlintct fish) recovered to 8, 91 nd 9% of control groups, respectively. The qingo nd the goldfish still hd the swimming ehviourl compenstions of higher TBmx nd higher f TBmx, respectively, ut it is still difficult to understnd the sustntil increse in U crit in ll three fish species ecuse the cudl fins recovered to less thn % of the control groups. Thus, the cudl fin size of the three selected fish species my not e the optiml fin re to sustin swimming. Fin size in mny fish species is suject to sexul selection ecuse fish with lrger fins hve greter success during reproduction (Wrner nd Schultz, 1992; Jordn et l., 2; Wilson et l., 21). Furthermore, the stronger unsustined swimming performnce is expected to support lrger cudl fin (Lngerhns, 29). Thus, cudl fin size my e trde-off etween sustined swimming performnce, unsustined swimming performnce, sexul selection nd other fctors. In fish with intct cudl fins, lrge fins cn hinder sustined swimming cpcity. One disdvntge of long fins is tht they cn increse the wet surfce re of the fish, creting more frictionl drg nd resulting in greter power requirements for swimming (Brrett et l., 1999; Plut, 2; Sinclir et l., 211). Thus, oth the drg nd the thrust decresed for the cudl-fin-regenerted fish. If the reduction in thrust were of similr order s the reduction in drg, then smll res of cudl fin regenertion could result in lrge recovery in U crit (We, 193). However, cudl-fin-regenerted fish my still hve other compenstory mechnisms. For exmple, the cudl-fin-regenerted fish could possily dpt to cudl fin deficiency, nd those fish my swim with more coordintion fter 2 dys of recovery. These issues require further reserch. The other interesting finding ws tht the shpes of the regenerted cudl fins were different from those of the intct cudl fins in ll three fish species, nd the Rs of the regenerted cudl fins were lower thn those of the intct cudl fins. lower R ws expected to e eneficil to enhncing fst-strt swimming performnce, which is rpid, high-energy swimming urst elicited y thretening stimuli nd is importnt for escpe from predtion (Lngerhns, 29), y improving the cpcity of ccelertion (Lngerhns nd Reznick, 29). These results demonstrte tht escpe from predtion my e the most importnt issue for cudl-fin-lost fish, cusing the recovery of fststrt swimming performnce to e prioritised. CKNOWLEDGEMENTS We re grteful to H. Yng nd X. Png for their ssistnce with the experiments. UTHOR CONTRIBUTIONS S.-J.F. conceived nd designed the experiments. C.F., Z.-D.C. nd S.-J.F. performed the experiments. C.F., Z.-D.C. nd S.-J.F. nlyzed the dt. C.F. nd S.-J.F. wrote the pper. COMPETING INTERESTS No competing interests declred. FUNDING This study ws funded y the Ntionl Science Foundtion of Chin (NSFC 31129), the Key Project of Science Foundtion of Chongqing (cstc213jjb23) nd the Project of Chongqing Science nd Technology Commission (CSTC, 21C11) (ll to S.-J.F.). REFERENCES kimenko, M.., Johnson, S. L., Westerfield, M. nd Ekker, M. (199). Differentil induction of four msx homeoox genes during fin development nd regenertion in zerfish. Development 121, 3-3. lsop, D. H. nd Wood, C. M. (199). 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