JOURNAL OF THEWORLD AQUACULTURE SOCIETY

Vol. 44, No. 1February, 2013

Improvement of Matrinxa, Brycon amazonicus , Larvicultureby Exposing Eggs to Triiodothyronine

Antonio Fernando Gervasio Leonardo

APTA Polo Regional do Vale do Ribeira, Registro, Sao Paulo, Brazil

Marcio Aquio Hoshiba and Elisabeth Criscuolo Urbinati1

Centro de Aquicultura, Universidade Estadual Paulista (UNESP), Via de Acesso Prof. PauloDonato Castelane, 14.884-900, Jaboticabal, Sao Paulo, Brazil

Jose Augusto Senhorini

Centro Nacional de Pesquisa e Conservacao de Peixes Continentais (CEPTA/ICMBio),Pirassununga, Sao Paulo, Brazil

AbstractThis work evaluated the effect of triiodothyronine (T3) on larviculture of matrinxa, Brycon

amazonicus . Oocytes of three females were pooled, fertilized with pooled semen of two males andseparated in four batches that were immersed in triiodothyronine solutions as follows: M1 (control –water); M2 (0.01 mg/L T3); M3 (0.05 mg/L T3); and M4 (0.1 mg/L T3). Triiodothyronine did not affectfertilization rate and number of hatched larvae. Weight of hatched larvae was significantly higher intreatments M3 and M4, as well as among larvae sampled at Day 12 in all treatments. After 12 d ofrearing, biomass gain was higher in the hormone treatments (M1 688 ± 569 mg; M2 2436 ± 562 mg;M3 3572 ± 569 mg; and M4 4129 ± 770 mg). In general, coefficients of variation of weight (CVw)and length (CVl) did not differ among treatments and cannibalism was registered between 36 and72 hours post-hatching (h.p.h.) without differences among treatments. Larval survival increased inthe hormone treatments (M1 26.5%; M2 37.6%; M3 40.6%; and M4 40.8%). The results indicate thatthe immersion of matrinxa eggs in triiodothyronine can promote beneficial effects to its larvicultureand indicate promising perspectives for culture of this tropical species.

Aquaculture in Brazil is increasing very fastand several fish species have been exploited.The genus Brycon has many species of mediumand large size widely distributed through Southand Central America (Howes 1982). Amongthose species, the matrinxa, Brycon amazoni-cus , native from Amazonian region, is a fishof high commercial value, successfully intro-duced into farming in many regions of Brazil(Roubach et al. 2003). In farming conditions,matrinxa has presented good performance dueto the artificial feed acceptance, fast growth,and low mortality rates. In spite of those advan-tages, matrinxa production has faced obstacles

1 Corresponding author.

in the initial stage, caused by larval cannibal-ism and low survival under intensive cultureconditions (Senhorini et al. 1998), as relatedto other species of the genus Brycon suchas Brycon lundi (Woynarovic and Sato 1990),Brycon moorei (Baras et al. 2000a), and Bryconorbignyanus (Senhorini et al. 2002; Landineset al. 2004; Leonardo et al. 2008). Matrinxastart cannibalizing each other about 36 h afterhatching when larvae present 50% of the swim-ming bladder insuflation (Bernardino et al.1993).

Thyroid hormones (T3, triiodothyronine, andT4, thyroxine) have been shown to be closelyinvolved in the developmental processes inmany species of fish (Brown et al. 1988; Reddyand Lam 1992; Liu and Chan 2002; Kang

© Copyright by the World Aquaculture Society 2013

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142 LEONARDO ET AL.

and Chang 2004). Those hormones have beentested to improve hatchery production of somefish species (Brown et al. 1989; Tachiharaet al. 1997; Stickney and Liu 1999). In tropicalspecies, exogenous triiodothyronine has shownpromising results to larviculture. T3 injectionto matrinxa, Brycon cephalus , females duringthe spawning induction increased the larvalsurvival (Urbinati et al. 2003), while promotinggrowth effect of T3 was verified using the sametechnique or when fertilized eggs of matrinxawere immersed in T3 (Urbinati et al. 2008). T3

egg immersion has also been shown to promotehigher survival in piracanjuba, B. orbignyanus ,(Landines et al. 2010). The aim of this studywas to evaluate the effect of triiodothyronine(T3) on the number of hatched larvae, growth,sibling cannibalism, and survival of matrinxa,B. amazonicus when eggs were exposed to thehormone.

Material and Methods

Pooled oocytes of three females were fer-tilized with pooled semen of two males andseparated in four batches corresponding tothe treatments: M1 (control – T3 free), M2

(0.01 mg/L T3), M3 (0.05 mg/L T3), and M4

(0.1 mg/L T3). Eggs were exposed during15 min to the treatment solutions and trans-ferred to 60-L conic incubators (three replicatesper treatment), being stocked 500 mL of eggsper incubator. The number of larvae was cal-culated immediately after hatching (Leonardoet al. 2004).

Thirty six hours post-hatching (h.p.h),larvae presented horizontal swimming andhunting behavior and were transferred to60-L tanks (larvae/L), with running waterand air flow. A powder ration (32% CP)was offered thrice daily, 0.5 mg per feeding,at 0900, 1300, and 1700 h. Additional wildplankton (500 organisms/larvae) was offereddaily at 0900 and 1700 h. Daily, at 0800and 1700 h, water temperature (25.2 ± 2.8 C),dissolved oxygen (7.8 ± 2.2 mg/L), and pH(6.5 ± 0.7) were measured. For every 3 d,total ammonia concentration (0.01 mg/L) andalkalinity (10.8 ± 1.7 mg/L) were measured.

Daily, before the first feeding, tanks weresiphoned.

Thirty larvae of each treatment (10 per tank)were randomly collected at 0 (36 h.p.h.), 1, 3,6, 9 and 12 d of rearing after the transfer to thetanks. Larvae were fixed in 2.5% Karnowskysolution for further weight (mg) and length (cm)measurement. Biomass was calculated as meanfinal weight × survival.

Coefficients of variation of body weight(CVw) and length (CVl) were calculated to ver-ify the size homogeneity of larvae at each sam-pling point using individual measurement: SDW

or L × 100/W or L, where W or L = averagebody weight or length, and SDW or L = standarddeviation of body weight or length. The stom-ach content of fixed larvae (n = 30) was ana-lyzed through stomach dissection using nee-dles and a stereomicroscopy (4.5×), and theoccurrence and type of food were regis-tered. Larval survival (S%) was estimated as(FN/IN) × 100, where IN = initial number oflarvae and FN = final number of fry.

Treatment groups were compared by one wayANOVA and means were compared by Tukey’smultiple range test with the level of significanceset at P < 0.05.

Results and Discussion

Fertilization rate, number of hatched larvaeand their body weight and length are presentedin Table 1. Hatching started 15 h after fer-tilization and triiodothyronine did not affectthe fertilization rate but promoted reductionof the number of hatched larvae. The free T3

(M1) and M3 (0.05 mg/L T3) treatments showeda higher number of hatched larvae (290,600and 257,000, respectively) compared with theM2 (0.01 mg/L T3) and M4 (0.1 mg/L T3) treat-ments (193,600 and 190,000, respectively). Tri-iodothyronine influenced the size of hatchedlarvae promoting the growth of M4 larvae thatwere 30% heavier and 15.3% longer than con-trol larvae. At 10 h.p.h., T3-treated larvae pre-sented complete horizontal swimming, whilecontrol larvae had incomplete horizontal swim-ming, dislocating to the water surface andfalling to the bottom of the aquaria, indicating

T3 ENHANCES MATRINXA LARVAE SURVIVAL 143

Table 1. Means (±SD) of fertilization rate, hatched larvae number, weight and length at hatching of matrinxa, Bryconamazonicus, larvae produced by eggs exposed to triiodothyronine (T3); n = 30. Means followed by the same letter in thelines are not different (P > 0.05).

T3 (mg/L)

M1 (0.00) M2 (0.01) M3 (0.05) M4 (0.1)

Fertilization rate (%) 89.4 ± 10.6a 85.5 ± 6.6a 78.36 ± 7.5a 86.93 ± 2.7a

Hatched larvae 290,600 ± 36.1a 193,600 ± 23.5b 257,000 ± 32.32ab 190,000 ± 17.32b

Weight (mg) 0.70 ± 0.05b 0.83 ± 0.07b 0.98 ± 0.06ab 1.04 ± 0.01a

Length (mm) 3.32 ± 0.06b 3.33 ± 0.04b 3.53 ± 0.23b 3.93 ± 0.15a

that the swimming bladder was not fully devel-oped. At 36 h.p.h., larvae of all treatmentspresented complete horizontal swimming andstarted to cannibalize each other, when theywere transferred to the rearing tanks for addi-tional 12 d. Triiodothyronine also influenced thelarval growth after hatching. Table 2 presentsthe body weight and length of matrinxa larvaeduring 12 d of rearing. At Day 12, the T3-treatedlarvae weight increased as the hormone con-centration increased compared to control lar-vae. There was a weight gain of 1.16, 3.31,and 4.55 mg, in M2, M3, and M4, respectively,compared with the control larvae, but larvallength did not differ significantly among treat-ments, except 3 days post hatching when therewas an increase in M3 and M4 larvae length.Larval biomass (Table 3) confirmed the stimu-lating effect of T3 on growth of matrinxa larvae.The administration of T3 to eggs promoted a

biomass gain of 71.7, 80.2, and 83.4% in M2,M3, and M4, respectively, compared with con-trol larvae. These results are in agreement withstudies on other fish species, which describedbeneficial effects of triiodothyronine in accel-erating embryonic and larval development andgrowth (Brown et al. 1988; Reddy and Lam1992; Brown and Kim 1995; Urbinati et al.2003; 2008; Kang and Chang 2004; Landineset al. 2010).

In general, the coefficient of variation ofweight (CVw) and length (CVl) did not differamong treatments, except for an increase inthe CVl of M4 larvae compared with M1 andM3 groups (Table 4), indicating that the sizeheterogeneity was not intensely influenced bythe hormone. Kim and Brown (1997) examinedthe actions and interactions of cortisol andthyroid hormones in the larval developmentof the Pacific threadfin, Polydactylus sexfilis .

Table 2. Means (±SD) of weight (mg) and length (mm) of matrinxa, Brycon amazonicus, larvae produced by eggsimmersed in triiodothyronine (T3), during the experimental period; n = 30. Means followed by the same letter in the linesare not different (P > 0.05).

T3 (mg/L)

Rearing (ds) M1 (0.00) M2 (0.01) M3 (0.05) M4 (0.1)

Weight (mg) Zero (36 h.p.h.) 1.68 ± 0.12a 1.86 ± 0.08a 1.88 ± 0.08a 1.88 ± 0.05a

1 1.99 ± 0.04a 2.00 ± 0.03a 2.02 ± 0.05a 2.03 ± 0.02a

3 2.70 ± 0.35a 2.39 ± 0.09a 2.77 ± 0.14a 2.84 ± 0.08a

6 6.39 ± 0.92a 5.96 ± 1.41a 6.46 ± 1.18a 9.3 ± 1.9a

9 9.30 ± 1.61a 9.51 ± 1.81a 8.84 ± 0.76a 12.2 ± 0.53a

12 10.5 ± 0.49b 11.7 ± 1.63ab 13.8 ± 2.10ab 15.1 ± 1.55a

Length (mm) Zero (36 h.p.h.) 6.25 ± 0.22a 6.29 ± 0.08a 6.45 ± 0.05a 6.51 ± 0.10a

1 6.33 ± 0.12a 6.35 ± 0.08a 6.49 ± 0.05a 6.56 ± 0.11a

3 6.26 ± 0.14c 6.27 ± 0.06bc 6.54 ± 0.08ab 6.7 ± 0.14a

6 8.05 ± 0.27a 7.49 ± 0.06a 7.64 ± 0.17a 7.9 ± 0.23a

9 8.9 ± 0.41a 8.4 ± 0.82a 8.2 ± 0.44a 8.6 ± 0.36a

12 8.8 ± 0.17a 8.9 ± 0.35a 9.4 ± 0.42a 9.5 ± 0.53a

144 LEONARDO ET AL.

Table 3. Biomass (mg) of matrinxa, Brycon amazonicus, larvae produced by eggs exposed to triiodothyronine (T3),after 12 d of rearing. Means followed by the same letter in the lines are not different (P > 0.05).

T3 (mg/L)

M1 (0.0) M2 (0.01) M3 (0.05) M4 (0.1 ppm)

Initial (36 h.p.h.) 1616 ± 112.5a 1792 ± 72.7a 1811 ± 79.9a 1804 ± 50.8a

Final 2304 ± 459.7b 4228 ± 602.1a 5383 ± 874.9a 5934 ± 755.8a

Biomass gain (mg/d) 688 ± 569.3b 2436 ± 562.6ab 3572 ± 797.0a 4129 ± 770.6a

According to their study, a hormone-inducedincrease in uniformity could lead to reducedcannibalism. Cannibalism among larvae andyoung juveniles of B. moorei , Perca fluviatilis ,and Dicentrarchus labrax was lower amonggroups with low-size heterogeneity (Baras et al.2000a; Kestemont et al. 2003). Differently fromthis study, reduced heterogeneity in growth ofthe progeny of matrinxa was observed whenfemales were injected with T3 (Urbinati et al.2003). At Day 1 of rearing, as well as at Day 0(only for body length in this case), when canni-balism was evident, the CVw and CVl tended todrop, but it was not associated to the intensityof predation and cannibalism (Table 5).

Intense cannibalism emerged, equally inlarvae of all treatments, at 36 h.p.h. until 72h.p.h. (Day 1 of rearing) as verified by thestomach content of larvae (Table 5), that startedto accept other types of food (plankton andration) only at Day 3. This “critical” periodof cannibalism was described in other Brycon(Senhorini et al. 1998; Baras et al. 2000a;Prieto-Mojica et al. 2002; Landines et al.2004). The stomach content showed feedingpreference of larvae by cladocerans in relationto copepods and ration, independent on thehormone treatment. Fregadolli (1993) studiedthe feeding selection of food organisms forpacu and observed that larvae preferred largerand more mobile preys such as cladocerans(Moina micrura and Diaphanosoma birgei )instead of rotifers and nauplii. Cyclopoidcopepods were also less selected due to bemore evasive. Only at Day 12, the consumptionof ration was expressive and was found in 23of the 30 sampled larvae. At Days 3, 6, and9 only few larvae accepted ration. Previous

study showed that matrinxa started to acceptration at 7 d of age (Senhorini et al. 2002).

Sibling predation by matrinxa larvae wasmore intense between 36 and 72 h.p.h., espe-cially by larger larvae. However, smaller larvaealso exerted intense cannibalism on deformedsiblings or in larvae that was ingesting aprey. Around 60 h.p.h., cannibals were able toingest the preys entirely. Baras et al. (2000b)described in B. moorei the different phasesof attacks. In the early phase of development,embryos attacked siblings of equivalent sizeor slightly larger than themselves, which wereincompletely ingested, sucked up to the headand regurgitated (Type Ia cannibalism) while2-d-old larvae performed complete ingestionbut could not digest the head of their prey,which was regurgitated (Type Ib cannibalism).One day later, all cannibals had turned to com-plete cannibalism (Type II). This study classi-fied the attacks registered at 36–48 h.p.h. andType II at 60–72 h.p.h., as Type I cannibalism.In matrinxatilde, the complete prey ingestionoccurred after 60 h.p.h.

Beneficial effect of triiodothyronine on thelarval survival of matrinxa can be observed inFig. 1. There was an increase of survival in M4larvae compared to the control group (40.8 and26.5%, respectively), while M2 and M3 groupsshowed intermediary values (37.6 and 40.6%,respectively). The higher biomass in the hor-mone treatments can be associated to the highersurvival and higher growth verified in thosegroups of larvae. Enhanced survival by effectof triiodothyronine was previously described infish. Brown et al. (1988) elevated the T3 contentof striped bass eggs by injecting females withT3 and found a positive and highly significantcorrelation between the concentration of T3 in

T3 ENHANCES MATRINXA LARVAE SURVIVAL 145

Table 4. Coefficient of variation of weight (CVw) and length (CVl) of larvae of matrinxa, Brycon amazonicus, producedby eggs exposed to triiodothyronine (T3), during the experimental period; n = 30. Means followed by the same letter in thelines are not different (P > 0.05).

T3 (mg/L)

Rearing (d) M1 (0.00) M2 (0.01) M3 (0.05) M4 (0.1)

CVw Zero (36 h.p.h.) 12.1 ± 6.4a 10.4 ± 3.3a 13.79 ± 3.2a 10.57 ± 2.2a

1 8.0 ± 1.5a 7.3 ± 2.1a 6.6 ± 2.3a 5.8 ± 2.7a

3 20.3 ± 5.5 15.25 ± 4.0a 16.1 ± 3.6a 14.7 ± 3.7a

6 32.8 ± 5.7a 21.4 ± 1.1a 32.7 ± 24.2a 31.1 ± 15.6a

9 34.6 ± 13.6a 22.9 ± 15.2a 20.5 ± 1.7a 26.0 ± 11.4a

12 17.7 ± 6.7a 8.7 ± 3.9a 17.3 ± 1a 13.0 ± 4.6a

CVl Zero 5.8 ± 0.8 5.7 ± 2.4a 4.5 ± 0.6a 3.5 ± 1.4a

1 4.4 ± 1.4a 3.7 ± 0.8a 3.1 ± 0.5a 2.7 ± 1.8a

3 5.3 ± 1.4a 3.3 ± 0.8a 5.3 ± 0.5a 4.6 ± 0.8a

6 4.6 ± 1.2b 7.0 ± 0.8ab 4.3 ± 2.1b 8.7 ± 1.1a

9 8.9 ± 3.7a 5.8 ± 2.1a 7.03 ± 1.6a 5.8 ± 3.2a

12 5.8 ± 0.8a 4.5 ± 4.0a 6.1 ± 5.1a 7.3 ± 1.9a

Table 5. Stomach content of matrinxa, Brycon amazonicus, larvae produced by eggs exposed to triiodothyronine (T3),during the experimental period; n = 30. M1 (T3 free, 0.0 mg/L); M2 (0.01 mg/L); M3 (0.05 mg/L); and M4 (0.1 mg/L)a

Feed items (units per stomach)

Rearing (d) T3 (mg/L) Cannibalism (%) Cladocerus Copepodae Ration

0 (36 h.p.h.) M1 50 0 0 EM2 50 0 0 EM3 60 0 0 EM4 50 0 0 E

1 (60–72 h.p.h.) M1 60 0 0 EM2 60 0 0 EM3 60 0 0 EM4 60 0 0 E

3 M1 0 2.6 ± 1.6 0 (4) + + + +M2 0 4.6 ± 3.3 1.0 ± 0.0 EM3 0 7.0 ± 4.0 0 (2) + + + +M4 0 5.6 ± 2.7 0 (4) + + + +

6 M1 0 6.2 ± 4.0 1.2 ± 0.4 EM2 0 7.0 ± 3.5 3.0 ± 0.0 (5) + + + +M3 0 7.7 ± 4.3 1.0 ± 0.0 EM4 0 10.4 ± 6.3 1.0 ± 0.0 E

9 M1 0 13.3 ± 8.1 1.3 ± 0.5 EM2 0 9.7 ± 4.2 2.0 ± 0.0 (1) + + + +M3 0 8.3 ± 1.5 0 (1) + + + +M4 0 12.0 ± 4.9 0 E

12 M1 0 5.1 ± 2.8 0 (1) + + + +/(6) + +M2 0 3.5 ± 1.6 0 (4) + + + +/(3) + +M3 0 7.8 ± 3.2 0 (1) + + + /(4) + +M4 0 9.6 ± 5.2 1.3 ± 0.5 (1) + + + /(1) + +

aRation: E (empty); + (1/4 full); + + (1/2 full); + + + (3/4 full); + + + + (full). Values in parentheses are number oflarvae with ration in the stomach.

the unfertilized eggs and the rate of survivalwithin the cohort. Following, Brown et al.(1989) monitored the survival of striped bassmaternally T3-treated through the fingerlingstage, under hatchery production conditions,

and found mean survival of 5.3% in the controlgroup against 22.3% of the experimentalgroup. The same enhancing effect of T3 inlarval survival was related by Tachihara et al.(1997), Kang and Chang (2004). In matrinxa,

146 LEONARDO ET AL.

M1 (0.0 mg/ L) M2 (0.01 mg/L) M3 (0.05 mg/L) M4 (0.1 mg/L)

b

aab

ab

Surv

ival

(%

)

60

40

50

30

20

10

0

Figure 1. Survival rate (%) of matrinxa, Brycon amazon-icus, fry produced by eggs exposed to triiodothyronine(T3), after 12 d of rearing.

higher survival was observed in progeny afterT3 mother injection (Urbinati et al. 2003).

However, the higher survival of larvae inthis experiment cannot be associated to thereduced cannibalism because there was nodifference in the stomach content of larvaein all treatments. The higher weight of T3

larvae at hatching might have provided betterconditions to their survival.

The survival rate found in this study (around40%) among T3-treated larvae in laboratoryconditions, utilizing only plankton and ration,is a promising result for matrinxa larviculturebecause of the low cost and easy handling. Sim-ilar or even higher (70%) results were describedin earth ponds culture of B. cephalus and B.orbignyanus (Senhorini et al. 1998, 2002) andof B. moorei (Baras et al. 2000a), but in thosecases, alternative fish prey was offered asfeeding. The results of this study indicate thatthe use of triiodothyronine by exposing the fer-tilized eggs to the hormone can bring beneficialeffects to the larviculture of the matrinxa andopen promising perspectives for the intensiveculture of this fast-growing tropical fish.

Acknowledgments

The authors extend their thanks to the tech-nician Joao Caetano and the researchers LuisAlberto Gaspar and Sandoval dos Santos Juniorfrom the National Center of Research and Con-servation of Freshwater Fish (CEPTA/ICMBio),for their support during the experiment.

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