Development of a Promising Fish Model (Oryzias melastigma) for Assessing Multiple Responses to Stresses in the Marine Environment

Table 3

Utilization of O.  melastigma as a research model for toxicological studies.

Responsive to	Toxicological research about	Age of fish	Exposure concentration and time	Main works	Main conclusions	References
Organic chemicals
WAFs	CYP1A-involved detoxification mechanism	3-week-old fish and adults	2.5, 5, 10, 20, 40, 60, 80, and 100% WAF for 24 h; 5% for 6, 12, 24, 48, 72, and 96 h	Transcript profiling of whole omCyp genes, enzyme activity and steroid hormones assay, omCyp1a mRNA expression in different tissues during different developmental stages, and effects of β-NF, BaP, and WAF on expression of omCyp1a	WAF induced CYP-involved detoxification mechanism but reduced steroidogenic metabolism; omCyp1a would be associated with the initiation of the cellular defense systems.	[25, 33]
PBDE-47	Immune-modulatory effects	Three-month-old	290 and 580 ng/day from 2 dpf to hatching	Correlation between BDE-47 body burden and complement gene expression (RT-PCR) in different genders	Genes studied were gender dependent (males > females); BDE-47 is not biotransformed in marine medaka.	[29]
	Maternal transfer	2- and 3-month-old	1.3±0.2 μg/day for 21 days	Accumulation of PBDE 47 in 2-month-old fish and maternal transfer of PBDE 47 from adult female medaka to eggs	PBDE 47 transfer is associated with lipid mobilization during egg production.	[42]
PFOS	Mitochondrial dysfunction	Embryos	0.25 and 1 mg/L from 2 dpf to 6 dpf	Sequence the RNA mixtures using Solexa/Illumina RNA-Seq at various developmental stages and after various types of exposure, and DGE and qRT-PCR analysis for relative gene expression	The mitochondrial dysfunction appears to be involved in multiple toxicological effects of PFOS on O.  melastigma embryos.	[27]
	Precocious hatching	Embryos	1, 4, and 16 mg/L from 2 dpf to hatching	Record the time for hatching, hatching rate and mortality of fry hatched within a week, and hatching enzymatic activity and RT-PCR analysis for gene expression	PFOS induced the hatching enzyme, leading to the precocious hatching of embryos and the decrease of larvae survival.	[10]
	Endocrine-disruptive effect	Embryos	1, 4, and 16 mg/L for 2 dpf, 4 dpf, and 10 dpf, respectively	The mortality and malformation rates, the transcriptional responses of the ER, AHR, and PPAR pathways to PFOS by RT-PCR, and quantification of PFOS in exposure solutions and medaka embryos	PFOS has estrogenic activity and endocrine-disruptive properties and could elicit gene responses in a stage-specific manner.	[28]
	Cardiac toxicity	Embryos	1, 4, and 16 mg/L for from 2 dpf to hatching	Cardiac morphology, heart rates and the SV-BA distance of the heart was measured; RT-PCR analysis of gene expression profiles was conducted.	PFOS affected the development and function of the heart in the marine medaka embryos.	[23]
	Immunotoxicity	Embryos	0, 1, 4, and 16 mg/L from 2 dpf to hatching	PFOS body burden, survival rates, and growth parameters of fish larvae during 17 dph, liver histological examination, and gene expression in fish larvae after LPS exposure for 12 h at 27 dph	The immunosuppression effects caused by PFOS could lead to functional dysfunction or weakness of the immune system in the fish larvae.	[26]
BPA	Cardiac toxicity	Embryos	200 μg/L for 2 dpf-incubation	Heart beat rate, SV-BA distance of embryos, body length and width, histology, and BPA-induced inflammation-related genes and heart-related genes	BPA induced cardiac toxicity of the O.  melastigma embryos.	[31]
PAHs (ANF, Pyr, Phe, and BaP)	Developmental malformations	Embryos	Different PAHs for 18 days	Deformity assessment, heart rate, heart elongation, hatch rate, and EROD and Caspase-3/7 activity assays of embryos exposed to PAHs with or without 100 μg/L ANF	Inhibition of CYP1A, EROD, and Caspase-3/7 activities can be used as indicator in the ecological early warning and PAHs detection.	[43, 44]
Estrogen (E2, EE2, NP, and BPA)	Estrogenic pollutants	Sexually mature	E2, EE2 (1, 10, 100, and 500 ng/L); NP, BPA (1, 10, 100, and 200 μg/L) for 7 days	E2-inducible choriogenins expression in embryos and yolk-sac larvae by end-point PCR; effects of EE2, BPA, and NP, respectively, on omChgh and omChgl expression by RT-PCR	The rapid inducibility (within 24 h) of omChgh by E2 during early developmental stages was found to be more estrogen sensitive than omChgl.	[34]
Benzotriazole	Reproductive effect	3-month-old	0.01, 0.1, and 1 mg/L for 4 and 35 days	Benzotriazole can induce Vtg and Cyp19a gene expression but inhibits the Cy1a1 gene expression (qPCR analysis).	Benzotriazole had adverse potential on the endocrine system.	[45]
Inorganic chemicals
DWNTs	Ecotoxicity data of DWNTs	48 h posthatching	10, 50, and 100 mg/L for 14 days	Mortality and total length of medaka fish larvae over 14 days exposed to different concentrations of stirred and sonicated double-walled carbon nanotubes.	So-DWNTs are more toxic than st-DWNTs; the dispersion method and size of aggregations should be considered in DWNT toxicity testing.	[46]
nZnO	Sublethal toxicities	<24 h	4 and 40 mg/L ZnO for 96 h	Stress responses in fish after acute exposure (SDS-PAGE)	nZnO did not display the same toxicity as ZnO towards the fish.	[40]
HgCl2	Hepatotoxicity and neurotoxicity	Weighing 0.5 ± 0.05 g	1000 μg/L for 8 h; 1 or 10 μg/L for 60 d	Protein expression profile in liver and brain exposed to HgCl2 (MALDI-TOF/TOF MS) and mercury accumulation and damaged liver ultrastructure in medaka	Hg hepatotoxicity might involve oxidative stress, cytoskeleton impairment, and a dysfunction in metabolism.	[37, 38]
Cd^2+, Hg^2+, Cr^6+, and Pb^2+	Toxic effects of heavy metals	Embryos and larvae	96 h and 14 d	The mortality, heart beat rate, and malformation rates	The fish species has relatively high sensitivity to heavy metal stress.	[47]
Detrimental organisms
Vibrio parahaemolyticus	Immunotoxicity	5-month old	6 × 105 cfu/fish for 6 h, 24 h and 48 h	qPCR analysis of the complement genes in liver; age-, tissue-, and gender-differences in the expression of hepcidin; hepcidin expression in hepatocyte by ISH	O.  melastigma can serve as a model to understand the basic biological processes related to immune function.	[30, 48]
K. brevis: PbTx-1	Neurotoxicity	Adult	0, 6, 8, 10, 12, 16 and 18 μg/L for 24 h; 6 μg/L for 2 days	Algal toxicity (toxic symptoms, 24 hour mortality, 1/LT50) and its supernatant, MeOH and TCM extracts of O.  melastigma; changes in protein profiles in medaka gill and brain exposed to PbTx-1	K. brevis-induced hypoventilation response in medaka; the down-regulation of several proteins involved in cell protection.	[36, 49]
C. marina	Ichthyotoxins of C.  marina	4–8 months-old	10,000 cells/mL for 0, 24, 48 and 60 h	Algal cell density, growth rate, their toxicity (toxic symptoms, 24-hour mortality, 1/LT50) and its supernatant, MeOH and TCM extracts to O.  melastigma	Fish susceptibility to C.  marina is related to its growth rate, but not to cell density; C. marina developed the hyperventilation response of the fish.	[49, 50]
Environmental stress
Hypoxia	Hypoxia-responsive	4-week old adult	1.8 ± 0.2 mg O2/L for 3 months; 12 weeks 1.8 mg O2/L for 24, 48 and 96 h	Adult male fish were processed for ISH and IHC; volume density indices of omTERT mRNA and protein, PCNA and TUNEL signals in liver hepatocytes after chronic exposure to hypoxia; expression of Tert, Hif  1α, Epo, Lepr, and Ho in tissues by RT-PCR	Hypoxia upregulates omTERT expression via omHIFhif-1 in liver and testis and the omLepR omLEPR expression demonstrated its independent control in endocrine and peripheral tissues.	[16, 22, 24]
	Ichthyotoxins of C.  marina	4–8 months old	7 mg/L, 6.0  mg/L and 1  mg/L DO for 60 h	Oxygen consumption rate, threshold lethal DO and correlation between body weight and survival time of marine medaka inside the sealed syringe	Fish susceptibility to C. marina is related to the susceptibility of the fish to hypoxia.	[50]
Salinity	Osmoregulatory mechanism	2.50 ± 0.30 cm	SW (35‰), BW (15‰), FW (0) for Three weeks or 1 month	Plasma osmolality, MWC, Na^+/Cl^− concentration, time course, NKCC1a-like protein expression, NKA activity, NKA-IR cell activity, NKA α-subunit mRNA and protein expression in gills in response to hypoosmotic challenge; salinity effects on multiple Fxyd mRNA and FXYD11 protein abundance; co-immunoprecipitation of NKA with FXYD11 and the localization of Fxyd11 mRNA in gill sections in freshwater-acclimated marine medaka	The expression pattern of branchial Fxyd11 was similar to that of Nkaα in the O.  latipes, but non-correlated expression patterns were observed in the O.  melastigma at both the mRNA and protein levels; the lowest NKA activities were found in the environments with salinities similar to their natural habitats.	[5, 7, 32]
	Ichthyotoxins of C. marina	4–8 months old	70‰ seawater and natural seawater.	The LT50 of marine medaka at different ages (4–8 months-old) exposed to 70‰ hypersalinity (70‰-SW)	Fish susceptibility to C. marina is not related to its tolerance to hypersalinity stress.	[50]

Notes: days postfertilization (dpf); days posthatching (dph); sinus venosus-bulbus arteriosus (SV-BA); lipopolysaccharides (LPS); β-naphthoflavone (β-NF); benzo[a]pyrene (BaP); phenanthrene (Phe); pyrene (Pyr); methanol (MeOH); chloroform (TCM); quantitative polymerase chain reaction (qPCR).