Toxicity of Zinc Oxide Nanoparticles on the Embryo of Javanese Medaka (Oryzias javanicus Bleeker, 1854): A Comparative Study

(1) Background: Zinc oxide nanoparticles (ZnO NPs) are widely applied in various human products. However, they can be extremely toxic for aquatic organisms, particularly fish. This research was conducted to determine the LC50 of ZnO NPs on the embryos of Javanese medaka (Oryzias javanicus) in ultra-pure, deionized, and dechlorinated tap water; (2) Methods: The experiments were conducted in a completely randomized design (CRD) with three replicates for six treatments for acute (0.100, 0.250, 0.500, 1.00, 5.00, and 10.00 mg/L) exposures for each type of water; (3) Results: The LC50 of ZnO NPs at 96 h was determined as 0.643 mg/L in ultra-pure water, 1.333 mg/L in deionized water, and 2.370 in dechlorinated tap water. In addition to concentration-dependent toxicity, we also observed time-dependent toxicity for ZnO NPs. In addition, the sizes of ZnO NPs increased immediately after dispersion and were 1079 nm, 3209 nm, and 3652 nm in ultra-pure, deionized, and dechlorinated tap water. The highest concentration of measured Zn2+ in exposure concentrations was found in ultra-pure water, followed by deionized and dechlorinated tap water suspensions. Furthermore, Javanese medaka showed high sensitivity to acute exposure of ZnO NPs in all types of water.

Reproductive Toxicity of 3,4-dichloroaniline (3,4-DCA) on Javanese Medaka (Oryziasjavanicus, Bleeker 1854)

Compound 3,4-dichloroaniline (3,4-DCA) is a metabolite of several urea herbicides and intermediate chemical of several industrial products. Moreover, 3,4-DCA has been frequently detected in aquatic ecosystems around the world. This aniline is more toxic than the parent chemicals, and it affects non-target organisms. This study evaluated a 21-day reproductive response of an emerging aquatic vertebrate model, Javanese medaka (Oryzias javanicus), exposed to 3,4-DCA. Fecundity and gonads histopathology were observed. The spawning rate and fertilisation reduced significantly in the highest exposed-group (250 µg/L). Gonadosomatic index (GSI) was significantly low in females exposed to 250 µg/L. No substantial structural alteration of male gonads. However, oocyte development and ovarian cell structure were disrupted in 250 µg/L exposed females. The gonadal developmental was not affected in the males; however, a significant reduction in the developmental of female gonads was observed at 250 µg/L. These results show that 3,4-DCA interfere with the reproduction of Javanese medaka through fecundity and alteration of gonadal tissues.

Behavioral Responses of Javanese Medaka (Oryzias Javanicus) Versus Zebrafish (Danio Rerio) in Open Field Test.

Background: Locomotion is integral for animal survivability. However, the understandings of locomotor that lead to exhibition of multiple complex behaviors of fish models in response to an open field environment still remain unresolved. To determine whether two different fish models, Javanese medaka and zebrafish have similar baseline locomotor activity in open field paradigm, an open field test was used. Results: Results showed that Javanese medaka exhibit increased in exploratory activity with lower anxiety responses; exhibit a steady habituation response in OFT paradigm and vice versa in zebrafish. Medaka also took longer duration to establish home-base in comparison to the zebrafish. Although no other motor responses were observed, both fish species displayed strong preference of left eye used to assess the OFT tank. Conclusion: Medaka exhibits slower locomotors activity, lower anxiety responses and steadily maintains its locomotion once they reached habituation. In comparison, zebrafish demonstrated bolder behavioral phenotypes where they showed faster locomotors activity, higher anxiety responses with similar habituation response to the Javanese medaka. Thus, this present study revealed that two different teleost aquatic model organisms, Javanese medaka and zebrafish have different behavioral phenotypes in open field test.

Biochemical Constituent of Ginkgo biloba (Seed) 80% Methanol Extract Inhibits Cholinesterase Enzymes in Javanese Medaka (Oryzias javanicus) Model

Background. Pathophysiological changes leading to the death of nerve cells present in the brain and spinal cord are referred to as neurodegenerative diseases. Presently, treatment of these diseases is not effective and encounters many challenges due to the cost of drug and side effects. Thus, the search for the alternative agents to replace synthetic drugs is in high demand. Therefore, the aim of this study is to evaluate the anticholinesterase properties of Ginkgo biloba seed. Methods. The seed was extracted with 80% methanol. Toxicity studies and evaluation of anticholinesterase activities were carried out in adult Javanese medaka (Oryzias javanicus). Phytochemical study to identify the bioactive lead constituents of the crude extract was also carried out using high performance liquid chromatography (HPLC). Results. The result shows activities with high significant differences at P<0.001 between the treated and nontreated groups. A bioactive compound (vitaxin) was identified with the aid of HPLC method. Conclusion. The presence of bioactive compound vitaxin is among the major secondary metabolites that contribute to increasing activities of this plant extract. High anticholinesterase activities and low toxicity effect of this plant show its benefit to be used as natural medicine or supplements.

Effect of Diuron on Embryo-Larval Development of Javanese Medaka (Oryzias javanicus, Bleeker 1854)

Some herbicides exert hormetic or biphasic non-monotonic dose-response (NMDR), which is one of the major challenges for ecological risk assessment (ERA) of pesticides pollution. In this study, fish embryo toxicity test (FET) with Javanese medaka (Oryzias javanicus) to sublethal concentration of diuron was determined. Inverted U-shape heart rate was observed at 3 days post-exposure (dpe) and 7 dpe. However, at 13 dpe the heart rate (104 &plusmn; 2.90 heartbeat/min.) decreased in 10.00 mg.L-1 exposed-embryos. At 20 dpe, hatchability and survival rate were reduced in 5.00 mg.L-1 and 10.00 mg.L-1 exposed groups. Hormetic developmental deformities were observed in embryo-larvae of Javanese medaka. The results revealed a biphasic effect of low concentrations of diuron on some morphological and physiological features of Javanese medaka embryo-larvae, which might be attributed to endocrine disruption of this herbicide. Further studies to support these effects were recommended.

Preliminary study of closed system transportation, rearing and observation of the eggs Oryzias javanicus (Bleeker 1854) from Tunda Island

Wild Oryzias javanicus from Tunda Island has potential as a native Indonesian aquatic ornamental fish and a model for research in the laboratory. The preliminary stage for raising wild fish is transporting from nature to the aquacul-ture environment. Generally, to minimize fish stress during transport in a closed system, anesthetics are added to the transport media. Furthermore, good adaptation in the aquaculture environment will lead to the process of reproduction as the ultimate goal of domestication of wild fish. The research objective is to analyze the transportation of closed systems and the rearing of O. javanicus post-transportation from Tunda Island. Research observations were carried out on behavior, survival, the number of eggs, and male: female sex ratio. Transport using an additional anesthetic treatment of 0.4 mL L-1 and without anesthesia, with fish density of 16 L-1. Anesthesia used is the commercial product Ocean Free® Special Arowana Stabilizer. Transportation is carried out for 11 hours. After that, rearing post-transportation is carried out for 16 days. The results showed that the transportation of O. javanicus can use a closed system without the addition of anesthesia with a density of 16 L-1 for 11 hours. In post-transport maintenance, fish begin active swimming on day 5, swim in groups continuously on day 6, start responding to natural food on day 3 and artificial feed on day 7, and produce a final survival of 91.67%. During maintenance, O. javanicus produces 104 eggs, 0.94 ± 0.06 mm in diameter and has an attaching filaments and a non-attaching filaments in the chorion. Oryzias javanicus is an egg depositor that can spawn with a 1: 1 and 1: 2 sex ratio.