Using medaka embryos as a model system to study biological effects of the electromagnetic fields on development and behavior.

Abstract

The electromagnetic fields (EMFs) of anthropogenic origin are ubiquitous in our environments. The health hazard of extremely low frequency and radiofrequency EMFs has been investigated for decades, but evidence remains inconclusive, and animal studies are urgently needed to resolve the controversies regarding developmental toxicity of EMFs. Furthermore, as undersea cables and technological devices are increasingly used, the lack of information regarding the health risk of EMFs to aquatic organisms needs to be addressed. Medaka embryos (Oryzias latipes) have been a useful tool to study developmental toxicity in vivo due to their optical transparency. Here we explored the feasibility of using medaka embryos as a model system to study biological effects of EMFs on development. We also used a white preference test to investigate behavioral consequences of the EMF developmental toxicity. Newly fertilized embryos were randomly assigned to four groups that were exposed to an EMF with 3.2kHz at the intensity of 0.12, 15, 25, or 60µT. The group exposed to the background 0.12µT served as the control. The embryos were exposed continually until hatch. They were observed daily, and the images were recorded for analysis of several developmental endpoints. Four days after hatching, the hatchlings were tested with the white preference test for their anxiety-like behavior. The results showed that embryos exposed to all three levels of the EMF developed significantly faster. The endpoints affected included the number of somites, eye width and length, eye pigmentation density, midbrain width, head growth, and the day to hatch. In addition, the group exposed to the EMF at 60µT exhibited significantly higher levels of anxiety-like behavior than the other groups did. In conclusion, the EMF tested in this study accelerated embryonic development and heightened anxiety-like behavior. Our results also demonstrate that the medaka embryo is a sensitive and cost-efficient in vivo model system to study developmental toxicity of EMFs.

AI evidence extraction

Main findings

Newly fertilized medaka embryos exposed continuously to a 3.2 kHz EMF at 15, 25, or 60 µT (vs 0.12 µT background control) developed significantly faster, with multiple developmental endpoints affected (e.g., somites, eye measures, midbrain width, head growth, and day to hatch). Hatchlings from the 60 µT group showed significantly higher anxiety-like behavior in a white preference test than other groups.

Outcomes measured

• Embryonic development rate
• Number of somites
• Eye width
• Eye length
• Eye pigmentation density
• Midbrain width
• Head growth
• Day to hatch
• Anxiety-like behavior (white preference test)

Suggested hubs

• animal-studies (0.9)
  In vivo developmental and behavioral effects assessed in fish embryos/hatchlings under controlled EMF exposure.

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    "study_type": "animal",
    "exposure": {
        "band": "ELF",
        "source": "other",
        "frequency_mhz": 0.0032000000000000001533495552763497471460141241550445556640625,
        "sar_wkg": null,
        "duration": "continual exposure from newly fertilized embryo until hatch"
    },
    "population": "Medaka embryos (Oryzias latipes) and hatchlings (4 days post-hatch for behavior test)",
    "sample_size": null,
    "outcomes": [
        "Embryonic development rate",
        "Number of somites",
        "Eye width",
        "Eye length",
        "Eye pigmentation density",
        "Midbrain width",
        "Head growth",
        "Day to hatch",
        "Anxiety-like behavior (white preference test)"
    ],
    "main_findings": "Newly fertilized medaka embryos exposed continuously to a 3.2 kHz EMF at 15, 25, or 60 µT (vs 0.12 µT background control) developed significantly faster, with multiple developmental endpoints affected (e.g., somites, eye measures, midbrain width, head growth, and day to hatch). Hatchlings from the 60 µT group showed significantly higher anxiety-like behavior in a white preference test than other groups.",
    "effect_direction": "harm",
    "limitations": [],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "medaka",
        "Oryzias latipes",
        "embryo",
        "developmental toxicity",
        "electromagnetic fields",
        "ELF",
        "3.2 kHz",
        "microtesla",
        "behavior",
        "anxiety-like behavior",
        "white preference test"
    ],
    "suggested_hubs": [
        {
            "slug": "animal-studies",
            "weight": 0.90000000000000002220446049250313080847263336181640625,
            "reason": "In vivo developmental and behavioral effects assessed in fish embryos/hatchlings under controlled EMF exposure."
        }
    ]
}

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