gills
C'était des branchies.
They were gills.
— Men in Black (1997)
Les dauphins n'ont pas de branchies.
Dolphins don't have gills.
Les poissons sont pourvus de branchies et de nageoires.
Fish have gills and fins.
Ni les baleines, ni les dauphins n'ont de branchies.
Neither whales nor dolphins have gills.