Cardinalfish

Photo: wingwatcher48 · CC BY-NC

The Mediterranean cardinalfish is a mouthbrooder: males carry fertilised eggs in the oral cavity for up to a month, fasting throughout. Schools of hundreds congregate in cave entrances and overhangs during the day, dispersing at night to feed on plankton. Their brilliant red colouration is thought to be camouflage in low-light cave environments where red wavelengths are absorbed first.