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Why can a weever fish sting be especially painful?

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Bluefin tuna swimming underwater in a group, with silvery bodies and streamlined shapes, near Japan. — perciform Bluefin tuna (*Thunnus thynnus orientalis*) in the waters near Japan.

A weever fish sting is exceptionally painful because the fish possesses a specialized venom apparatus designed to inject toxins into a victim. These venomous structures include sharp spines located on the first dorsal fin and on the opercular (gill cover) area.123

The dorsal spines feature a grooved structure that houses a venom gland, allowing for the direct delivery of toxins when the spines penetrate the skin. When a person steps on or handles a weever fish, these spines can inflict an immediate, intense sensation described as burning, stabbing, or crushing. This pain often spreads and intensifies rapidly, sometimes leading to severe systemic reactions such as swelling, numbness, nausea, delirium, and, in extreme cases, convulsions or loss of consciousness. Because there is no known antidote for weever fish venom, the injury is considered a significant danger to humans in shallow waters.31