JOURNAL OF THE Vol. 4, No. 6 WORLD AQUACULTURE SOCIETY Decemer, 29 Impct of Bckground on Color Performnce of Flse Clownfish, Amphiprion ocellris, Cuvier Inyh Ysir School of Biologicl Sciences, Flinders University, GPO Box 21, 51 SA Adelide, Austrli, nd Deprtment of Mrine Sciences, Hsnuddin University, Mkssr 9245, Indonesi Jin G. Qin 1 School of Biologicl Sciences, Flinders University, GPO Box 21, 51 SA Adelide, Austrli Astrct Color performnce of flse clownfish, Amphiprion ocellris, Cuvier ws first exmined t four color ckgrounds (lue, green red, nd white) for 4 wk, then ll fish were trnsferred to white ckground for nother 4 wk to test whether the impct of ckground colors on fish skin could hve lsting effect when the environment colors re chnged. The experiment ws conducted in 1-L rectngulr plstic uckets with three replictes. Thirty fish were stocked in ech ucket nd three fish were rndomly smpled from ech tnk in Weeks 1, 4, nd 8. The color hue, sturtion, nd rightness were quntified using imge nlysis. In ddition to the whole ody nlysis, ech fish imge ws divided into ventrl nd dorsl prts to exmine the ody position-dependent response. Furthermore, color differences mong the dorsl fin, nl fin, ventrl fin, nd cudl fin were lso quntified. Blue or green ckground enhnced red ornge color on fish skin, wheres white ckground mde fish color righter. Irrespective of ckground color, the dorsl side of fish exhiited more red ornge, ut the color ws less right nd less sturted thn tht of ventrl side. Upper fins (dorsl nd cudl fins) were more red ornge in lue ckground thn in white ckground. Trnsferring fish from colored ckgrounds to white ckground mde the fish skin nd fins righter, the color of ventrl ody nd ventrl fins less sturted, nd the ottom fins more yellow ornge. The results indicte tht lue or green ckground could strengthen the ornge color, wheres white ckground mde fish color less sturted ut righter. The impct of ckground on the performnce of fish color is temporry nd likely to dispper when environmentl color chnges. Fish color cn e ltered y environmentl fctors through the rerrngement of chromtophores in the skin (Bgnr nd Hdley 1973; Sugimoto 1993). Chnges in color hue nd pttern re considered s result of physiologicl dpttion through chromtophore relloction or result of morphologicl dpttion y vrying the mount of pigmentry mterils under skin. According to Bgnr (1998), the chnge of ckground color could provoke physiologicl color dpttion, commonly known s cmouflge, to lessen predtor prey interctions. Cryptic colortion enles nimls to chnge their color property nd ptterns to lend into the ckground (Moyle nd Cech 24). Most color chnges in fish result from 1 Corresponding uthor. Copyright y the World Aquculture Society 29 724 the migrtion of melnophores, drk rown pigment cells, xnthophores, nd iridophores (Oshim et l. 1989). Tnk color is known to influence survivl nd growth of fish lrve (Dury et l. 1996; Oshim et l. 1989; Tmzouzt et l. 2), proly ecuse contrsting ckground enles etter prey visuliztion nd cpture efficiency (Mrtin-Roichud nd Peterson 1998). Previous studies hve minly focused on the comprison of tnk colors s contrsting ckground, or etween lck nd white tnks (Oshim et l. 1989; Dury et l. 1996; Downing nd Litvk 2), ut hve not een conducted cross rod color ckground. Bckground color could not only impct the feeding success ut lso ffect the fish color performnce. During the culture of qutic
BACKGROUND COLOR REGULATING FISH COLOR 725 nimls, chnges in pigmenttion pttern nd intensity re induced y chnging the tnk color (Fujimoto et l. 1991; Bker et l. 22). The color of the quculture environment hs reportedly ffected the color of red porgy, Pgrus pgrus (Vn der Slm et l. 25), Atlntic cod, Gdus morhu (Brnsden et l. 25), sole, Sole sole (Ellis et l. 1997), nd medk, Oryzis ltipes (Sugimoto 1993). The response of fish skin color to ckground color vried from fish species nd ge. Red porgy, P. pgrus, kept in white ckground hd lighter color thn when they were kept in red ckground (Vn der Slm et l. 25). Similrly, sole, S. sole, could mtch their skin color tone to the surrounding ckground under cptivity (Ellis et l. 1997). However, the lrve of Atlntic cod, G. morhu, kept in red nd gry ckgrounds showed no significnt difference on their skin color (Brnsden et l. 25). Fox (1957) reported tht no vrition of xnthophyll ws oserved in juvenile trout, Fundulus prvipinnis,whenfishwere trnsferred from drk to light continers or even to totl drkness for 6 wk. Inconsistent results were found with immture opleye, Girell nigricns, where the rte of color loss ws more rpidwhenthefishwerekeptinwhiteckground thn in yellow or red ckground (Sumner nd Fox 1935). Despite the discrepncy mong fish species, these reports support the ide tht fish kept in prticulr ckground color for certin period of time could not only chnge their skin color ut lso lter the responsiveness of melnophores to neurl nd hormonl fctors tht control the chromtophores motility (Oshim et l. 1989). Flse clownfish, Amphiprion ocellris, re one of the most populr ornmentl fishes ecuse of their color pttern, ehvior, nd ese of hndling in quri (Ysir nd Qin 27). According to Wnitz et l. (23), during 1997 22, flse clownfish ws the most common mrine qurium species covering 15.6 of the totl numer of fish exported worldwide nd over 25 into Europen countries. Thus, clownfish hve een considered the goldfish of mrine quri nd its vlue is judged y skin color (Hoff 1996). Ysir nd Qin (29) reported tht low light intensity could righten the skin color of clownfish, nd right ornge color could dd to the commercil vlue in n qurium trde. Bsed on the color composition of clownfish, we further provided four ckground colors, lue, green, red, ndwhite,tothefishfor4wk,ndthenseprtely moved ll fish to white ckground. With this design, we imed to investigte the impct of ckground colors nd their lsting effect on color performnce of the clownfish. In this study, we not only nlyzed the color response of the whole fish, ut lso quntified the color of the dorsl ody, ventrl ody, nl fin, cudl fin, dorsl fin, nd ventrl fin. The result could provide insight into the strtegies to design pproprite ckground environments for frming nd keeping ornmentl fish. Mterils nd Methods Experimentl Design nd Procedure Three month-old, A. ocellris (29.2 ± 3.36 mm stndrd length), were used in the experiment. All fish were htched nd rered in rown tnks under lortory conditions t 26 27 C. The experimentl fish were cclimtized y feeding on geltine-sed diet without crotenoid ddition. The experiment ws conducted in twelve 1-L plstic uckets with four ckground colors (red, green, lue, nd white) with white s control. Three replictes were used in tretment nd ech ucket ws stocked with 3 fish. After the fish were llocted to ech ucket, three fish were rndomly collected from ech ucket s the initil smple in Week 1. Three fish were then susequently smpled ech time t the end of Weeks 4 nd 8 using the sme smpling protocol s in Week 1. The uckets were rndomly suspended inside two 6-L tnks tht were supplied with sewter in recircultion system treted with io-filter nd mechnicl filter. An irstone ws plced into ech tnk for wter circultion nd ertion. The ottom of ech ucket ws cut open nd replced with white plstic screen (1 mm mesh) llowing wter exchnge. In
726 YASIR AND QIN ddition, nother irstone ws plced inside the ucket to fcilitte wter exchnge. Ech ucket ws cpped with plstic mesh to prevent fish escping. Light intensity ws 2 25 lx, provided y four uls (36 W, Osrm, Germny) locted 2 m ove the tnks. Oxygen level ws 6 mg/l, slinity ws 27 28, nd temperture ws 26 27 C. The light period ws controlled t 14 h light: 1 h drk. During the 8-wk experiment, the fish were fed twice dy with geltine-sed diet contining se perch, Lutjnus mlricus, flesh (8), vitmin C (5), nd geltin (15) y weight. In Week 4, ll fish in the red, green, lue, nd white uckets were seprtely trnsferred into new white uckets to test whether fish color gined in the colored ckgrounds could e retined. Prior to visul nlysis, live fish were nesthetized with tricine methnesulfonte (MS- 222) t concentrtion of 7 mg/l. MS-222 is wter solule compound which could reduce fish stress ut did not produce ny visully detectle color chnge. To further ssess the impct of MS-222 on fish color during nesthesi, fish imges were tken in 5-min intervl for 3 min, nd no significnt chnge ws detected over time through imge nlysis. The durtion of tking photogrphs for ech experimentl fish ws only 2 5 min; therefore, neither the nesthetic tretment nor the durtion for tking imges ffected fish color mesurements. Soon fter the fish imges were tken, ech fish ws plced in seled plstic g covered with luminum foil. The specimen ws frozen t 2 C until crotenoid nlysis. The sme protocol ws used throughout the experimentl smpling. Procedures for imge nd crotenoid nlyses were descried in detil in Ysir nd Qin (28). In rief, photogrphs were tken under four nturl white color uls. A digitl cmer ws situted on n djustle rm etween the two light sides. The cmer ws set up 25 cm ove the fish nd could cpture the whole fish imge long with yellow nd red reference crds (Kodk, CAT 152 7662, Q-14) underneth the continer. The imge ws nlyzed with Adoe Photoshop softwre (version 7..1). In ddition to the nlysis for the whole ody skin, the fish ody ws further divided into the dorsl prt nd the ventrl prt for color nlysis. Furthermore, four fish fins cudl fin, dorsl fin, ventrl fin, nd nl fin were seprtely scnned for color nlysis to test the fin position-dependent effect. The hue sturtion rightness (HSB) color model ws used to quntify the color property (Georgiev et l. 25). The HSB model reks the color into three components: the hue (i.e., how pure the color is), the percentge of sturtion (i.e., how much the color is), nd the rightness. Hue is the ctul color nd is mesured in ngulr degrees round the cone strting nd ending t red, which is equl to or 36 (e.g., yellow = 6, green = 12, nd lue = 24). Sturtion is the purity of the color, mesured in percentge from the center of the cone () to the surfce (1). At sturtion, hue is meningless. Brightness is mesured in percentge from lck () to white (1). At rightness, oth hue nd sturtion re meningless. Crotenoids were extrcted from fish skin nd ll fins with solvent cetone: hexne (7:3 v/v) for 1 min (Ysir nd Qin 29). Norml phse high performnce liquid chromtogrphy (HPLC) ws pplied using Lun 3 μ silic (2) 1 Å(15 4.6 mm) with security gurd crtridge silic (4 3. mm; Phenomenex) nd hexne : cetone (81:19 v/v). The flow rte ws 1.1 ml/min with 2-μL injection. The detector ws set in wvelength of 474 nm. Totl mount of crotenoids (μg/g skin) ws otined from the sum of stxnthin, β-crotene, cnthxnthin, nd zexnthin. Nturl sources of cnthxnthin, β-crotene, zexnthin, nd stxnthin (Sigm) were used to mke the stndrd solution for the HPLC nlysis. Stndrd solution ws mde y diluting the stock solution into different concentrtions prior to the HPLC nlysis. Sttisticl Anlysis The dt were sttisticlly nlyzed using SPSS (version 13) with three protocols. The first test ws one-wy repeted ANOVA to nlyze the impct of ckground color on the
BACKGROUND COLOR REGULATING FISH COLOR 727 color property (hue, sturtion, nd rightness) of the whole fish skin nd the pigment composition (stxnthin, cnthxnthin, β-crotene, nd zexnthin) over time. To further explore the effect of ckground on skin color, the fish ody ws divided into dorsl nd ventrl prts. In this test, time nd ody prts were treted s within-suject fctors nd ckground ws etween-suject fctor to exmine interctions mong time, ckground color, nd the response of different ody prts. Finlly, the impct of ckground on four fins cudl fin, dorsl fin, nl fin, nd ventrl fin ws evluted using repeted mesure ANOVA with time nd fins s within-suject fctors nd the initil ckground color s the etweensuject fctor (Tle 2). If significnt difference etween or within sujects ws detected, pirwise comprisons with Bonferroni test were used. The significnt level of difference ws set t P<.5. Results Whole Body Repeted mesure ANOVA showed tht the ckground color significntly ffected the color hue of whole fish skin (P =.4; Tle 1; Fig. 1). Fish color ws more red ornge (low hue vlue) in lue or green ckground thn in white ckground (P <.5, Bonferroni test), wheres no color difference etween red nd white ckgrounds or etween lue nd green ckgrounds ws detected (P >.5). For color sturtion, there ws n interction etween ckground color nd time (P =.38; Tle 1). After 4-wk exposure to colored ckgrounds, fish did not lter color sturtion (P >.5), ut when these fish were seprtely moved from the color ckground to white ckground for 4 wk, fish showed higher color sturtion in the white ckground thn those previously exposed to colored ckgrounds (P <.5; Bonferroni test; Fig. 1). Tle 1. Repeted mesure ANOVA tle showing procedures of dt nlysis nd the impct of ckground color on the color response (hue, sturtion, nd rightness) of the whole ody nd dorsl ventrl ody prts. Bckground color ws the etween-suject fctor, while time nd ody position were within-suject fctors. The vlues with old numers represent significnt differences. Hue Sturtion Brightness Source df MS F P df MS F P df MS F P Whole ody Body prts (dorslventrl) Between-sujects effects BC 3 9.97 1.198.4 3 38.81 3.44.92 3 38.71 3.492.7 Error 8 8.914 8 12.745 8 11.86 Within-sujects effects Week 2 26.87 1.862.187 2 8.375.682.52 2 26.137 15.719.1 Week BC 6 22.682 1.572.219 6 36.477 2.972.38 6 31.6 1.877.147 Error (week) 16 14.429 16 12.275 16 16.549 Between-sujects effects BC 3 173.474 11.2713.3 3 118.924 9.456.5 3 72.258 3.439.72 Error 8 15.391 8 12.577 8 21.1 Within-sujects effects Body prt 1 31.952 23.398.1 1 548.681 45.761.1 1 2385.283 3388.954.1 Body prt BC 3 3.287 2.214.164 3 2.746 2.256.159 3 1.366 1.941.22 Error (ody prt) 8 1.485 8 1.217 8.74 Week 2 32.544 1.13.356 2 129.8 9.128.2 2 433.119 29.657.1 Week BC 6 29.533 1.1.458 6 5.184 3.551.2 6 44.787 3.67.34 Error (week) 16 29.56 16 14.133 16 14.64 Body prt week 2 1.973 1.272.37 2 17.23 7.52.15 2 6.563 3.419.58 Body prt week 6 1.87.7.653 6 2.286.995.461 6 1.25.651.689 BC Error (ody prt 16 1.552 16 2.297 16 1.92 week) BC = ckground color.
728 YASIR AND QIN Degree 5 25 8 4 6 3 Hue Blue Green Red White Sturtion Blue Green Red White Brightness Figure 1. Responses of whole fish skin color hue, sturtion, nd rightness to ckground color (lue, green, red, nd white) over time. All fish were seprtely trnsferred from color ckground to white on Week 4. The vlues represent the mens ± SE. Mens with different letters denote significnt differences (P >.5). Fish rightness ws not chnged y the ckground color (P =.7; Tle 1), ut ws significntly influenced y time (P =.1). After fish were exposed to color ckground for 4 wk, fish rightness ws slightly reduced, ut when fish were moved from color ckgrounds to white ckground for 4 wk, fish rightness ws significntly incresed (P <.5; Bonferroni test) regrdless of previous exposure to colored ckgrounds. Dorsl nd Ventrl Body Regrdless of ckground color, the dorsl prt showed more red ornge (i.e., low hue vlue) thn the ventrl prt (P =.1; Tle 1; Fig. 2). Considering oth dorsl nd ventrl prts, the ckground color significntly ffected fish color hue (P =.3; Tle 1; Fig. 2). The dorsl or ventrl prts were more red ornge in the lue, green, or red ckground thn in the white ckground (P <.5), wheres no color difference etween lue nd green, or etween lue nd red ckgrounds ws detected (P >.5; Bonferroni test; Fig. 2). The ventrl color ws more sturted thn the dorsl color throughout the experimentl period (P <.1; Tle 1; Fig. 2). However, the impct of ckground on the color sturtion of oth dorsl nd ventrl prts depended on time (P =.2; Tle 1; Fig. 2). After fish were exposed to different color ckgrounds for 4 wk, no significnt difference in fish color sturtion ws oserved etween fish in vrious ckgrounds (P.11; Bonferroni test; Fig. 2). After these fish were seprtely trnsferred to white ckground for 4 wk, the fish hving een continuously kept in white ckground exhiited more sturted color thn fish previously exposed to lue, green or red ckground (P.6). In other words, more sturted fish color ws only oserved in fish tht hd een in white ckground for 8 wk. Fish color sturtion did not differ mong lue, green, nd red ckgrounds (P.64). Regrdless of ckground color, the ventrl ody ws righter thn the dorsl prt nd this sttus remined unchnged throughout the experimentl period (P =.1; Tle 1; Fig. 2). However, the impct of ckground on the color rightness of oth dorsl nd ventrl prts depended on time (P =.34; Tle 1; Fig. 2). One week fter the experiment strted, fish in the white ckground ws significntly righter thn fish kept under green ckground (P =.31; Bonferroni test), ut did not differ from fish kept under lue or green environment (P.165). In comprison, fter fish were exposed to different ckground colors for 4 wk, no difference in fish color rightness ws detected mong white, lue, red, nd green ckgrounds (P >.5) nd this sttus did not chnge fter these fish were seprtely
BACKGROUND COLOR REGULATING FISH COLOR 729 Degree 5 25 Hue Dorsl Ventrl 9 6 3 Sturtion Dorsl Ventrl 7 35 Brightness Dorsl Ventrl Degree 5 25 c 9 6 3 Blue Green Red White 7 35 Blue Green Red White Blue Green Red White Figure 2. Impct of ckground colors on fish color hue, sturtion, nd rightness etween ventrl nd dorsl ody over time. The vlues represent the mens ± SE. Mens with different letters denote significnt differences (P <.5). trnsferred to white ckground (P >.5; Fig. 2). Fins The hue vlue of fish fins rnged from 34 (red ornge) to 52 (yellow ornge) nd were significntly ffected y the interction of fin position nd ckground (P =.3; Tle 2; Fig. 3). The dorsl fin of fish in lue ckground ws significntly more red ornge (low hue) thn tht in white or red ckground (P.17; Bonferroni test; Fig. 3), wheres no hue difference of the dorsl fin ws detected mong the white, green, nd red ckgrounds (P >.5). Similrly, the cudl fin of the fish in lue ckground ws more red ornge thn in white ckground (P.2; Fig. 3), ut no hue difference of the cudl fin ws detected mong the white, green, nd red ckgrounds (P >.5). Bckground color did not ffect the hue of either nl fin or ventrl fin (P.19). The color hue of fish fins ws lso significntly ffected y the interction of fin position nd time (P =.1; Tle 2; Fig. 3). In contrst to the ckground effect, the hue of ottom fins (nl nd ventrl fins), rther thn upper fins (dorsl nd cudl fins), ws significntly ffected y the time of exposure to color ckgrounds. Both nl nd ventrl fins ecme yellowish (i.e., high hue vlue) fter fish were kept in color ckground for 4 wk. Interestingly, the yellow ornge on these fins continued incresing nd ecme significnt fter these fish were seprtely trnsferred to white ckground for four more weeks (P.5). The chnge of overll fin color sturtion depended on time (P =.1; Tle 2). The fin sturtion did not chnge in the first 4 wk (P >.5; Bonferroni test; Fig. 3), ut decresed fter these fish were trnsferred to white ckground for 4 wk (P <.5). Regrdless of ckground color, the nl fin, cudl fin, nd dorsl fin were slightly less sturted y the end of the Week 4, ut ecme significntly lesssturtedyweek8whenthesefishwere trnsferred from colored ckgrounds to white ckground for 4 wk (P <.9; Fig. 2). After eing kept in color ckgrounds for 4 wk, the overll fin rightness incresed fter fish were trnsferred to white ckground for 4 wk(p<.5; Fig. 3). Bckground color did not significntly ffect the rightness of fins (P =.327; Tle 2), ut it seemed tht ottom fins were righter thn upper fins with nl fin eing the rightest (73) followed y ventrl fin (69), cudl fin (6), nd dorsl fin (49). The vrition of fin rightness depended
73 YASIR AND QIN Tle 2. Repeted mesure ANOVA tle showing procedures of dt nlysis nd the impct of ckground color on the color response (hue, sturtion, nd rightness) of the whole ody, dorsl ventrl ody prts (D V), nd fins. Bckground color ws the etween-suject fctor, while time, ody position nd fins were within-suject fctors. The vlues with old numers represent significnt differences. Hue Sturtion Brightness Source df MS F P df MS F P df MS F P Between-suject effects BC 3 154.641 5.63.3 3 124.83 5.325.26 3 26.336 1.343.327 Error 8 3.541 8 23.3 8 19.64 Within-sujects effects Fins 3 67.479 2.633.1 3 568.119 77.873.1 3 499.311 797.44.1 Fins BC 9 7.885 2.64.3 9 11.784 1.487.29 9 8.417 1.637.161 Fins Error (fins) 24 3.28 24 7.922 24 5.141 Week 2 42.161 1.38.298 2 668.72 1.462.1 2 267.925 6.679.8 Week BC 6 41.859 1.299.313 6 132.454 2.72.114 6 98.154 2.447.72 Error (week) 16 32.222 16 63.916 16 4.116 Fins week 6 51.27 19.779.1 6 29.589 2.595.29 6 31.568 4.68.2 Fins week BC 18 4.91 1.896.4 18 9.475.831.657 18 8.311 1.71.47 Error (fins week) 48 2.589 48 11.41 48 7.76 BC = ckground color. 6 Hue Blue Green Red White 8 Sturtion 8 Brightness Degree 3 4 4 Degree 6 3 AF CF DF VF Week 1 Week 4 Week 8 9 6 3 Week 1 Week 4 Week 8 9 6 3 Week 1 Week 4 Week 8 AF CF DF VF AF CF DF VF AF CF DF VF Figure 3. Impct of ckground on the color hue, sturtion, nd rightness of nl fin, cudl fin, dorsl fin, nd ventrl fin. The vlues represent the mens ± SE. Mens with different letters denote significnt differences (P <.5). on the fin position nd time of exposure to the ckground color (P =.2; Tle 2). The rightness of ventrl fin did not vry over time (P >.5), ut the nl fin, cudl fin, nd dorsl fin ecme righter fter fish were trnsferred from color ckgrounds to white ckground for 4 wk (P <.5). Crotenoid Anlysis Crotenoids composition nlysis showed tht β-crotene ws the dominnt pigment nd ccounted for >85 of the crotenoids during the experiment (Fig. 4). No pigments were ffected y the ckground color (P.449; Tle 3), ut ll pigments except β-crotene were significntly ffected y time (P.7; Tle 3). The mount of stxnthin in fish skin significntly incresed fter 4 wk in the color ckgrounds, ut significntly reduced when fish were moved from colored ckgrounds to white ckground for 4 wk (P <.5). The mount of cnthxnthin ws significntly
BACKGROUND COLOR REGULATING FISH COLOR 731 Tle 3. One-wy repeted mesurement ANOVA results for the impct of ckground color on pigment contents of the fish skin. The vlues with old numers represent significnt differences. Astxnthin β-crotene Cnthxnthin Zexnthin Source df MS F P df MS F P df MS F P df MS F P Between-sujects effects BC 3.591.98.449 3 4.252.485.72 3.813.5.984 3.388.96.96 Error 8.63 8 8.765 8 16.312 8 4.44 Within-sujects effects Week 2 15.21 16.222.1 2 43.683 6.86.7 2 174.79 11.841.1 2 47.975 16.69.1 Week BC 6.595.635.71 6 1.874.292.932 6.453.31.99 6.113.38.99 Error (week) 16.938 16 6.419 16 14.71 16 2.986 BC = ckground color. reduced y 4-wk exposure to the colored ckgrounds (P <.5; Fig. 3), nd the cnthxnthin reduction ws not recovered fter fish were moved from the colored ckgrounds to the white ckground for 4 wk. In contrst, the mount of zexnthin ws slightly incresed y the 4-wk exposure to the colored ckgrounds, ut its mount continued incresing despite the chnge from colored ckgrounds to white ckground for 4 wk (P <.5). Discussion The present study demonstrted tht ckground color could ffect the color expression of clownfish fter short term exposure. The reduction of hue vlue in lue or green ckground enhnced red ornge color of the whole fish skin, while fish kept in white ckground ppered yellowish. The rection of clownfish to the ckground color is similr to Austrlin snpper (Dooln et l. 27). The skin color ws significntly lighter in snpper held in white cges compred with snpper held in lck cges. The monochromtic color of the experimentl cges used y Dooln et l. (27) proved to e the overwhelming fctor governing the skin lightness of snpper. In nother study, Vn der Slm et l. (24) reported tht red porgy, P. pgrus, kept on white ckground were significntly lighter thn those kept in red ckground. However, in our study, the red ckground did not seem to differ from the white ckground in regulting fish hue nd rightness. Dooln et l. (27) hypothesized tht the cge color ppers to hve directly influenced the neuroendocrine system of snpper, which hs in turn influenced the physiologicl stte of the melnophores contined in their skin. Although the mechnisms involved for color dpttion to the ckground remin to e resolved, Rotllnt et l. (23) reported tht red porgy, P. pgrus, weremuch less stressed in white ckground thn gry or lck ckground s shown y the level of stress hormones. The choice of tnk color for the quculture use should consider the growth nd stress responses of fish to the color ckground. The white tnk seems more suitle for growing snpper ecuse of low stress to fish nd the light fish color it produces (Rotllnt et l. 23), wheres lue or green tnks my e more suitle to produce red ornge clownfish, the fvorite color for most qurium hoyists. One of the motivtions of this study ws to test whether the gined color trits in fish from colored ckgrounds would lst if the clownfish were moved to neutrl color environment (i.e., white). In snpper, Dooln et l. (27) reported tht fish held in white cges ecme lighter in 2 d, ut we found tht the clownfish took much longer to significntly fde their color hue fter removl to white ckground. The trnsfer of fish from lue uckets to white uckets incresed the hue vlue, nd fish ecme pler (i.e., chnging from reddish to yellowish), which mens reduction of color qulity in clownfish. Vn der Slm et l. (24) found tht fst pling response
732 YASIR AND QIN Figure 4. The chnge of percent contents of stxnthin, β-crotene, cnthxnthin, nd zexnthin over time. The vlues represent mens ± SE. to white ckground is form of neurl regultion of the melnophores. Rodrigues nd Sumpter (1984) recognized tht pigmenttion is controlled oth hormonlly nd neuronlly. In fish, fst color chnges usully result from neuronl control nd longer-term morphologicl color chnges from hormonl control (Fujii 2). Generlly, fst color chnges involve quick relloction (dispersion or ggregtion) of pigment grnules (melnosomes) within the derml melnophores, while the morphologicl color chnge involves prolifertion or poptosis of melnophores, which my e comined with incresed or decresed sensitivity of the melnophores to regultory signls (Sugimoto et l. 1997). A 4-wk process of pling in clownfish my e more relted to hormone control ut further study is needed to confirm this presumption. One of the most successful chromtic dpttions in fish is the dorsl ventrl pigment pttern in which the dorsl skin is drkly colored, wheres the ventrum is light. In this study, the dorsl ody of clownfish hd lower hue vlue (more reddish ornge) thn the ventrl ody, ut the ventrl ody color ws righter nd more sturted. This sttus did not chnge over time nd the response of oth sides to ckground color ws similr. In recent study, Ysir nd Qin (29) reported tht the ventrl prt of clownfish ws righter thn the dorsl prt regrdless of light intensity, ut the dorsl prt ws lwys more ornge thn the ventrl prt. Similrly, the color difference etween dorsl prt nd ventrl ody in red porgy ws not ffected y the light level mnipultion (Chtzifotis et l. 25). Cerd-Reverter et l. (25) suggested tht the development of the dorsl ventrl pigment pttern in fish is chieved y melniztion inhiition fctor which inhiits melnolst differentition nd supports iridophore prolifertion in the ventrum. However, in clownfish, neither light level mnipultion nor color ckground seems le to chnge the dorsl ventrl color trits. Fin color is n importnt trit in ornmentl culture nd rood selection (Chpmn nd Fitz-Coy 1997). However, most ttention to fin color hs een pid in txonomy studies. For instnce, the color pttern of the cudl fin is useful criterion for identifiction of two species of tilpi nd their hyrids (Noh et l. 26). In quculture prctice, Htnk (1997) identified tht the idel fin color of tiger puffer, Tkifugu ruripus, ws otined in lck tnk. Ysir nd Qin (29) noted tht low light provoked righter fins especilly on cudl nd dorsl fins nd righter light strengthened ornge color on fish fins. In this study, lue ckground enhnced red ornge on oth dorsl fin nd cudl fin compred with white ckground. Interestingly, in the first 4 wk, the nl fin nd ventrl fin showed more red ornge, ut their color ecme yellow ornge fter eing kept to white ckground for 4 wk. The trnsfer from colored ckgrounds to white ckground lso reduced color sturtion on the nl fin, cudl fin, nd ventrl fin, ut incresed color rightness on the nl fin, cudl fin, nd dorsl fin. Our result suggests tht responses of
BACKGROUND COLOR REGULATING FISH COLOR 733 fish ody skin nd fins to color ckground re similr, lthough the ottom fins (nl nd ventrl) re reltively less sensitive to the environmentl mnipultion. The white screen (1 mm mesh) on the ottom of ech ucket might e potentil fctor influencing the response of the ottom fins to the color ckground. Nevertheless, despite the quick response of fish skin nd fins to the color ckground mnipultion, the color chnge derived from the colored ckground seems to e temporl rther thn permnent lterntion. β-crotene ws the most dominnt pigments in clownfish, followed y zexnthin, cnthxnthin, nd stxthin, ut none of these pigments ws significntly ffected y ckground mnipultion. Tnk et l. (1992) suggested tht pinkish ornge of clownfish should contin high mount of zexnthin. Through mnipulting light intensity, Ysir nd Qin (29) found tht zexnthin ws enhnced in clownfish y low light illumintion, ut there ws no evidence tht zexnthin ws ffected y the color ckground chnge in this study. Fish nd other vertertes cnnot synthesize crotenoids (Mtsuno 21) nd hve to rely on feed tht contins crotenoids (Allen 1991). Although clownfish could temporrily chnge the color expression through chnging light intensity (Ysir nd Qin 29) or ckground color (this study), it is unlikely to chnge the pigment composition through environmentl mnipultion. It is, therefore, necessry to further test the response of color expression of clownfish to diet mnipultion. In quculture, high fish density could lter the color expression of the skin of red porgy, P. pgrus, s result of stress (Rotllnt et l. 23). Vn der Slm et l. (24) further reported tht high density (25 kg/m 3 ) could drken the skin color of red porgy, compred to the low density (1 kg/m 3 ) tretment. In our study, the fish density ws reduced y 2 s result of smpling efore the end of the experiment, which might contriute to the color chnge over time. The possile impct of stocking density on the color chnge of clownfish needs further investigtion. Acknowledgments We would like to thnk Sndr Mrshll for the technicl support during the experimentl period nd we lso pprecite the vlule comments y Michel Bull on this mnuscript. This reserch ws prtilly supported y the AusAid postgrdute study scholrship to I. Y. Literture Cited Allen, G. R. 1991. Dmselfishes of the world. Hns A. Bensch, Germny. Bgnr, J. T. 1998. Comprtive ntomy nd physiology of pigment cells in nonmmmlin tissue. Pges 9 4 in V. J. Hering, R. A. King, J. P. Ortonne, J. J. Nordlund, nd R. E. Boissy, editors. The pigmentry system: physiology nd pthophysiology. Oxford University Press, USA. Bgnr, J. T. nd M. E. Hdley. 1973. Chromtophores nd color chnges: the comprtive physiology of niml pigmenttion. Prentice Hll Interntionl, London, UK. Bker, R. T. M., A. M. Pfeiffer, F. J. Schoner, nd L. Smith-Lemmon. 22. Pigmenting efficcy of stxnthin nd cnthxnthin in fresh-wter rered Atlntic slmon, Slmo slr. Animl Feed Science nd Technology 99:97. Brnsden, M. P., G. M. Butterfield, J. Wlden, L. A. McEvoy, nd J. G. Bell. 25. Tnk colour nd dietry rchidonic cid ffects pigmenttion, eicosnoid production nd tissue ftty cid profile of lrvl Atlntic cod (Gdus morhu). Aquculture 25:328 34. Cerd-Reverter, J. M., T. Hitin, H. B. Schioth, nd R. E. Peter. 25. Gene structure of the goldfish gouti-signling protein: puttive role in the dorsl-ventrl pigment pttern of fish. Endocrinology 146:1597 161. Chpmn, F. A. nd S. A. Fitz-Coy. 1997. United Sttes of Americ trde in ornmentl fish. Journl of the World Aquculture Society 28:1 1. Chtzifotis, S., M. Pvlidis, C. D. Jimeno, G. Vrdnis, A. Sterioti, nd P. Divnch. 25. The effect of different crotenoid sources on skin colortion of cultured red porgy (Pgrus pgrus). Aquculture Reserch 36:1517 1525. Dooln, B. J., M. A. Booth, P. L. Jones, nd G. Alln. 27. Effect of cge colour nd light environment on the skin colour of Austrlin snpper Pgrus urtus (Bloch & Schneider, 181). Aquculture Reserch 38:1395 143. Downing, G. nd M. K. Litvk. 2. The effect of photoperiod, tnk colour nd light intensity on growth of lrvl hddock. Aquculture Interntionl 7:369 382.
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