|PD/A CRSP Twentieth Annual Administrative Report
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Subcontract No. RD010E-A
The Ohio State University, Columbus, Ohio
|Konrad Dabrowski||US Principal Investigator|
|Mary Ann Abiado||US Principal Investigator|
|Kyeong-Jun Lee||Postdoctoral Researcher|
|Gustavo R. Montes de Oca||Ph.D. Student (Mexico; CRSP funded from January 2002)|
|Kyle Ware||Undergraduate Student (from January 2002)|
|Wilfrido Contreras-Sánchez||Host Principal Investigator|
|Gabriel Márquez Courturier||Host Country Principal Investigator|
|Maria de Jesus Contreras Garcia||Host Country Undergraduate Student Researcher|
|Guadalupe Morales Lara||Host Country Undergraduate Student Researcher|
|Ronald P. Phelps||US Principal Investigator (Collaborator)|
|Fernando Alcántara Bocanegra||Host Country Principal Investigator|
|Salvador Tello||Host Country Principal Investigator|
|Rebaza A. Mariano||Host Country Study Leader|
|Sonia D. Taboada||Host Country Study Research Associate|
|Maria Esther Palacios||Graduate Student (Peru; CRSP funded from June 2002)|
This subcontract was awarded funding to conduct the following Tenth Work Plan investigations:
Note: OhSU collaborates with Universidad Juárez Autónoma de Tabasco and Auburn University on 10RCR1. In addition, OhSU is a collaborator with Southern Illinois University, Carbondale (SIUC), and University of Arkansas at Pine Bluff on the Peru Project, Sustainable Aquaculture in the Peruvian Amazon. SIUC is the lead institution for the Peru Project. The methods for 10RCR1 were modified.
Dabrowski, K., J. Rinchard, J.S. Ottobre, F. Alcántara, P. Padilla, A. Ciereszko, M.J. de Jesus, and C. Kohler. Effect of oxygen saturation in water provided to broodstock and embryos of Piaractus brachypomus on viability of larvae. Aquaculture. (in press)
PD/A CRSP Annual Meeting at San Diego, California, 31 January 2002. (Dabrowski)
All-male populations are desirable in tilapia (Oreochromis niloticus) aquaculture because males demonstrate superior growth compared to females. The increasing use of 17a-methyltestosterone (MT) for sex reversal in tilapia, especially in developing countries, necessitates comprehensive studies on the fate of MT and its metabolites in order to address human and environmental safety issues. Alternative methods of sex reversal, such as the use of phytochemicals from locally available plants, need to be explored to minimize the cost of producing monosex populations and to prevent the occurrence of intersex fish and paradoxical feminization associated with high dosages and prolonged use of MT.
Quercetin is a flavonoid commonly present in plants. It has been considered an aromatase inhibitor in fish and has been shown to manifest mutagenic and enzyme-inhibitory properties. In order to evaluate the possibility of the use of quercetin as an alternative to MT for sex reversal in tilapia, four semi-purified, casein/gelatin-based diets were used. The diets [1) control, 2) quercetin 1%, 3) vitamin C (1,000 ppm), and 4) quercetin 1% plus vitamin C (1,000 ppm)] were formulated and fed to tilapia (genetically all-male XY) larvae, average weight 9.6 ± 1 mg. Fish were distributed (150 fish per aquarium) and held in a water recirculation system consisting of 12 glass aquariums maintained at 27 ± 2°C, with three replicates per diet. Ten fish per replicate (Bouin's fixative) were sampled after three to five weeks to evaluate histological appearance of gonads (presence of cellular apoptosis) or any changes in the sex ratio within treatments. On week 20, sex determination by squash aceto-carmine method was performed. Histological observations of gonads will be presented in the final report. Preliminary results show that quercetin inclusion in the diet did not have any effect on sex determination in the fish studied. A toxic consequence, manifested by promoting apoptosis of gonad cells, as described in other fish species, was not observed.
The possible positive effects of the interaction of quercetin and ascorbic acid (vitamin C) were examined on the growth performance of all-male tilapia. Individual final weight, hepatosomatic index (HSI), and condition factor (CF) were evaluated for each dietary treatment. After 19 weeks no significant differences (P > 0.05) were observed in these parameters. The average values were mean weight 7.7 ± 2.3 g, CF 0.98 ± 0.21, and HSI 1.18 ± 0.48%. Preliminary determinations of the level of total ascorbic acid in whole body in fish fed for 15 weeks showed 15.8 ± 2.8, 10.6 ± 2.2, 28.3 ± 7.0, and 31.4 ± 2.7 µg g-1 wet weight for diets 1 through 4, respectively. Parallel studies with the same diets using mixed-sex populations of tilapia were performed at the Universidad Juárez Autónoma de Tabasco (UJAT), Tabasco, Mexico. After eight weeks similar growth was observed in all treatments (final fish weight 0.73 ± 0.15 g). Data on quercetin and ascorbic acid levels in several tissues (whole body, liver, and intestine) and possible interactions among dietary components will be presented in the final report.
Quercetin and ascorbic acid exhibit a potent antioxidant activity, characteristics that make them excellent dietary additives for ultraviolet (UV) damage prevention. One of the many consequences of UV exposure is skin damage due to the formation of free radicals; therefore, administration of antioxidants that scavenge these molecules might be a promising strategy to minimize such impairment. Results from this study will be presented in the final report.
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