Study was conducted to assess the histopathological damage of Gill, Liver and Brain in common carp, Cyprinus carpio after sublethal exposure to Quinalphos. Exposed to sublethal concentration (One tenth (1/10th, 0.75 µl/L) of commercial grade quinalphos (25% Emulsified Concentration) for 1, 7, 14, 21 and 30 days and a parallel control was run simultaneously. Gill, Liver and Brain of exposed individuals exhibited some remarkable changes in their histology in comparison to control. Prominent changes include shrinkage of the glomerulus, and dilation of tubular lumen. Vacuolization, desquamation, hydropic swelling and hyaline degeneration of tubular epithelium is also observed. Cyst formation and hemorrhage also appear in certain specimens. Duration of exposure appears to have a profound effect on Gill, Liver and Brain as with increasing duration of exposure histopathological damages become more severe.

ABSTRACT. Circulating levels of estradiol, vitellogenin and prostaglandins could be references of oocytes quality in the aquaculture industry. This study evaluated the performance of 17β-estradiol (E2) and vitellogenin (Vtg) levels in plasma and prostaglandins in oocytes (PGE 2) during the reproductive period of Oreochromis niloticus in a commercial farm in Ecuador. Adults fish females were treated with estradiol-synthetic (ES) and tilapia pituitary extracts (TP) during 25 days. For quantification of E2 and PGE 2, an enzyme-linked immunosorbent assay (ELISA) was used, while for Vtg relative quantification a Western blot analysis was performed. Circulating E2 concentrations were different during the first week of follow-up (P < 0.05) resulting in different levels of Vtg per treatment (P < 0.05) affecting on gonadal growth. The ovaries had an asynchronous development, where the mature oocytes proportions were higher with ES and TP than control. Relative fecundity was different between treatments (P < 0.05), where TP generated 15.7 ± 5.8 oocytes per g of spawning female. Furthermore, concentrations of PGE 2 were different between treatments (P < 0.05). The information reported in this study will be useful to improve the reproduction methods and have some biological signals before ovulation in tilapia commercial culture.

The ability of microalgae to remove nitrogen and phosphorus from wastewater has been used in recent years as an alternative treatment for discharges from livestock slurry, which generate a negative environmental impact on vulnerable ecosystems. With this background and the feasibility of using microalgae, we have evaluated the effect of Chlorella sp. and Synechocystis sp., in removing contaminants from the pig manure collected from El Prado ESPE. Slurry samples were collected, filtered and autoclaved, and the supernatant was further diluted to three different concentrations of 40%, 60% and 80%. The microalgal growth and pollutants removal property was evaluated up to 15 days in batch culture. The cell density was determined by counting in a Neubauer hemocytometer, and the pollutants removal was analyzed by standard colorimetric methods. The microalgae Chlorella sp. showed a maximum cell growth of 1.70 ± 0.09 x10 7 cells/mL at 60% effluent concentration on day 6. While Synechocystis sp. showed a maximum growth of 1.04 ± 0.05 x10 7 cells/mL, at 60% concentration on day 9. On the other hand, there exists a competition when microalgae used as a consortium. The cell growth of Chlorella sp. was higher at all concentrations compared to Synechocystis sp.. Overall, efficiency of pollutant removal were between 40% and 90%, which demonstrate the feasibility of using microalgae in tertiary swine wastewater treatment.

Aquaculture is a productive activity in economic growth due to market productivity which supports many Ecuadorian communities. However, exotic species has been the basis of this activity without considering the endemic and mega-diverse component of Ecuador. On the other hand, current aquaculture systems use a lot of water, generating discharge of nitrogen and phosphorus, causing a negative impact on natural watersheds. The present investigation focused on the diversification of aquaculture production and environmental care, through the polyculture of tilapia and river prawn, in a Biofloc system, which allows reducing the use of water, space, and food, taking advantage of all the nutrients of the aquatic environment without generating pollutant residues, from a carbon-nitrogen ratio of 20:1. The research project was developed under laboratory conditions at 2.728 amsl, for 8 weeks in pre-breading stages. Two factors were established in the study: type of culture (monoculture and polyculture) and production systems (traditional and biofloc), with three replicates. In the Biofloc system, the environmental variables such as temperature, pH, and oxygen did not show any significant differences between treatments (p≤0.05), while conductivity and total suspended solids increased during the test, and the nitrification processes stabilized at day 28 with values of 0.06±0.01 and 0.35±0.09 ppm in ammonium and nitrite respectively. The bacterial load was higher in the Biofloc system (113.66x103 CFU/ml) with predominance of Bacillus sp. and Pseudomonas sp. The bioflocs showed greater volume in polyculture (17.62 ml/L) and 26% of protein. Under these considerations, the best productive performance was detected in the Biofloc polyculture with a total productivity of 142.86g/m2 (p≤0.05). Therefore, diversification of species, types and culture systems are viable for aquaculture in Ecuador, generating an interaction between the chemical and biological components, allowing productive processes to be sustainable.

The release of heavy metals in to the aquatic environment causes water pollution problems because of their toxicity, persistence and bioaccumulation. Lead has no known role to play in the human body that is physiologically relevant, and its harmful effects are myriad. Lead from the atmosphere and soil ends up in water bodies thus affecting the aquatic organisms. This situation has thus prompted numerous investigators to study on the effects of this heavy metal on the biological functions of aquatic organisms, particularly on the antioxidant enzyme activity in fish. In the present investigation the effect of lead acetate (heavy metal) on antioxidant enzyme activity was evaluated in the fresh water fish Labeo rohita. The experimental fish were treated with sub lethal concentration of lead acetate (0.015 mg/ L) for 120 hrs. Spirulina was used as supplementary feed during the experimental period. We observed various lead induced lipid peroxidation (LPO), antioxidant enzyme (SOD and CAT) changes and Spirulina supplementary feed therapeutic efficiency was observed in the gill and liver tissues of the fish. All the experimental data are statistically significant at p<0.05% level. The present study was under taken the toxic effect of lead acetate on Labeo rohita fish and chelating property of Spirulina.