10/14/2026
In several cardinalfish species, the male takes responsibility for protecting the eggs by carrying them inside his mouth. This unusual reproductive behavior is known as paternal mouthbrooding, and it turns the fish's buccal cavity into a temporary shelter for developing offspring.
After spawning, the male collects the fertilized egg mass and holds it inside his expanded mouth. The eggs remain there during incubation, protected from many of the dangers they would face if left exposed on the seafloor or attached to surrounding vegetation.
Mouthbrooding comes with an important trade-off. Because the mouth is occupied by the developing eggs, males often reduce feeding during the incubation period. The parent must balance its own energy needs against the protection of its offspring until development is complete.
When the eggs hatch, the young eventually leave the father's mouth and begin living independently. This strategy demonstrates a remarkable form of parental investment in fish, where the adult sacrifices feeding opportunities and uses part of its own body as a protective nursery.