A Lamella (plural: lamellae) is a soft, thin plate that is attached to the bony gill arches in a fish's gills.
Lamellae also appear in other animals, for example water birds and ducks, as a filter when feeding for organisms or plant matter.
Scanning electron microscopy image of the gill filament and lamellae from a 18-day-old larval Yellowfin Tuna (Thunnus albacores).