Effect of dietary tryptophan (TRP) on copper toxicity was investigated in common carp, Cyprinus carpio. Fish were randomly distributed into two triplicate treatments (control and TRP) and fed control (TRP = 3.1 g kg(-1)) or TRP (TRP = 8.1 g kg(-1)) diets over a 2-week period. Then, both treatments were subjected to 10 mg l(-1) copper sulfate over a 7-day period. Mortality and serum cortisol, glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), sodium, potassium, and chloride levels were recorded at 0, 24, 72, 120, and 168 h post-copper exposure. There was no mortality in the TRP group, whereas the control group mortality was started at 120 h post-copper exposure (21.7 ± 7.6 %) and reached 61.7 ± 10.4 % at the end of the experiment. Cortisol, glucose, ALT, and AST levels significantly (P < 0.05) increased after copper exposure in both groups; however, the control group showed significantly higher levels than the TRP group. In both groups, sodium decreased after copper exposure and did not return to the pre-exposure values. Potassium levels significantly increased 24 h post-copper exposure in both groups and remained significantly elevated in the control group at 72 h, when fell to the pre-exposure values in the TRP group. No significant changes were observed in the chloride levels in any groups. It is concluded that dietary TRP is capable to increase common carp tolerance to copper toxicity via mitigating copper-induced stress rather than restoring gill dysfunction and hydromineral imbalance.

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This study investigated the effects of two source carotenoids on the hepatosomatic index (HSI) and the gonadosomatic index (GSI) of the goldfish (Carassius auratus). For this experiment, six diets containing concentrations of 50, 100, and 150 mg carotenoid kg-1 of synthetic astaxanthin and β-carotene were added to a basic carp diet, while one group of fish was fed a control diet (no added carotenoids). Fiberglass tanks were used for the study, which was performed from January to April of 2013. During the breeding period, the hepatosomatic (HSI) and gonadosomatic (GSI) indices were examined monthly, along with the total carotenoid levels in the ovaries and livers of female goldfish broodstock. A significant positive correlation was observed between total carotenoids in both the liver and ovary tissues and GSI after 90 and 120 days of the experiment. The HSI was not affected by the carotenoid-enriched diets. However, the carotenoid-enriched diets resulted in greater accumulation of carotenoids in the gonads. β-carotene-enriched diets (B150) led to greater accumulation of carotenoids in the liver after 90 days. Lastly, we found that diets containing higher levels of astaxanthin and β-carotene improve the GSI in goldfish broodstock. Efecto de la astaxantina y β-caroteno en la dieta, sobre los índices gonadosomático y hepatosomático, composición de la gónada e hígado en reproductores de carpa dorada Carassius auratus (Linnaeus, 1758) RESUMEN. Este estudio investiga el efecto de dos fuentes de carotenoides sobre el índice hepatosomático (HSI) y el índice gonadosomático (GSI) de la carpa dorada (Carassius auratus). En este experimento, se adicionaron seis dietas conteniendo concentraciones de 50, 100 y 150 mg carotenoide kg-1 de astaxantina sintética y β-caroteno a una dieta de carpa, mientras a otro grupo de peces se le suministró una dieta control (sin carotenoides). Se utilizaron estanques de fibra de vidrio de enero a abril 2013. Durante el periodo experimental, el HSI y el GSI se examinaron mensualmente junto con la concentración de carotenoides totales en ovario e hígado de hembras. Una correlación positiva significativa se encontró entre el total de carotenoides aportados en la dieta y el hígado, ovario y el GSI después de 90 y 120 días de experimento. El HSI no fue afectado por las dietas enriquecidas con carotenoides. Sin embargo, las dietas con carotenoides mostraron un mayor acumulación de carotenoides en las gónadas. La dieta con β-carotenos (B150) presentó una mayor acumulación de carotenoides ____________________ Corresponding editor: Enrique Dupré 364 Latin American Journal of Aquatic Research en el hígado después de 90 días. Finalmente, se encontró que las dietas que contenían el nivel más alto de astaxantina y β-caroteno mejoraron el GSI en los reproductores de carpa dorada.