Some color change may be rapid and temporary. Alarmed fish, for instance, often change color. Some bottom-dwelling fishes change color almost instantly to match the substrate. Some marine species of bony fishes produce light through a chemical reaction process called bioluminescence. Light production may occur through photophores, luminescent cells on the fish, or by light-producing bacteria that live in or on the fish in a symbiotic relationship.
All fishes have fins.
Various bony fish families show various degrees of fin fusion and reduction. Fins help stabilize or propel the fish in the water. Except in the lungfishes and the coelacanth, fins lack bones. In Actinopterygians, fins are supported by structures called rays. Some bony fishes have soft, flexible fin rays.