What sensory adaptation is nearly exclusive to South American knifefish (Gymnotiformes) for mapping their environment?

Answer

Self-generated, low-voltage electrical discharges for electro-navigation.

These species rely almost exclusively on self-generated, low-voltage electrical discharges, functioning similarly to echolocation, because they are often nearly blind.

What sensory adaptation is nearly exclusive to South American knifefish (Gymnotiformes) for mapping their environment?
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