A taxonomic family name for hagfishes, jawless aquatic animals with seven gill openings.
From Greek 'hepta' meaning 'seven', 'trema' meaning 'opening', and '-idae' the standard suffix for animal families in taxonomy.
Hagfishes are absolutely bizarre—they secrete slime so thick and strong they can tie themselves in knots to escape predators. And scientists named their family after their seven gill holes because that was the weirdest thing about them.
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