Glyphosate is globally a widely used herbicide, yet there is little information on their toxicity to marine fishes. Java medaka, a small tropical fish native to coastal areas in several Southeast Asian countries, is viewed as a suitable candidate for toxicity test and thus was used for this study. Java medaka adults were cultured in the laboratory and the fertilized eggs of the F2 generation were exposed to different concentrations of glyphosate-based herbicide (100, 200, 300, 400 and 500 ppm) until they hatched. The survival and hatching rates of the embryos, changes in the heart rate and morphological impairments were recorded. Generally, survival and hatching percentage decreased as glyphosate concentration increased. Absence of pectoral fin(s) and cornea, permanently bent tail, irregular shaped abdomen, and cell disruption in the fin, head and abdomen are among the common teratogenic effects observed. Furthermore, risk factor also increased with the increased in glyphosate concentrations.
17beta-estradiol (E2) is a female hormone which is known to be one of the strongest estrogenic chemicals in the environment. The present study investigated the effects of E2 on the reproduction of the estuarine fish, Java-medaka (Oryzias javanicus). Starting from the embryonic stages, Java-medaka was exposed for 6 months to 9.5, 16, 68, 159 and 243 ng/l of E2. The fecundity of Java-medaka exposed to E2 levels >16 ng/l was significantly lower than that of the control. The appearance of secondary sexual characteristics seemed to be inhibited by exposure to 159 and 243 ng/l E2. Vitellogenin concentrations in the liver of male fish exposed to 68, 159 and 243 ng/l were significantly higher than that of the control. Thirty-three and sixty percent of male fishes exposed to 159 and 243 ng/l, respectively, had testis-ova. These results suggest that reproduction in the Java-medaka, especially the male fish, could be affected by exposure to E2 concentrations greater than 16 ng/l.
This study was conducted to investigate the median lethal concentration (LC50) of copper pyrithione (CuPT) at 96-hr exposure on adult Javanese medaka (Oryzias javanicus) in revealing toxicological effects of CuPT contamination in the tropical area. Wild stock fishes were acclimatized for 14-days prior analysis. Triplicate of test tanks for seven test concentrations were placed with ten fishes each, this includes two control tanks. The behaviour of the tested fishes was manually observed through a camera. The LC50 of CuPT at 96-h was found to be 16.58mg/L. Tested fishes swam slowly in vertical movement and swam fast towards food during feeding time as the sign of stress behaviour. Meanwhile, fishes in the two control groups swam actively in a horizontal manner and no excitement during feeding time. No mortality in control groups. Results indicate CuPT to be toxic to Javanese medaka at low concentration and caused behavioural stress.