A photophore is a light-emitting organ which appears as luminous

Luminescence

Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...

 spots on various marine animals, including fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 and cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors http://tolweb.org/accessory/Cephalopod_Photophore_Terminology?acc_id=2015. The light

Light

Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

 can be produced from compounds during the digest

Digest

Digest can refer to any of the following:*A condensed collection or compendium of writings:**Pandects, or "The Digest", a digest of Roman law**A tax digest...

ion of prey, from specialized mitochondrial cells in the organism, called photocytes

Photocytes

A Photocyte is a cell that specializes in catalyzing enzymes to produce light . Photocytes typically occur in select layers of epithelial tissue, functioning singly or in a group, or as part of a larger apparatus ....

 ("light producing" cells) , or, similarly, associated with symbiotic

Symbiosis

Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 bacteria in the organism that is cultured

Microbiological culture

A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...

.

The character of photophores is important in the identification of benthic

Benthos

Benthos is the community of organisms which live on, in, or near the seabed, also known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.Many organisms...

 fishes.

Photophores on fish are used mainly for attracting food or confusing predators.

Photophores are also on some cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s, most notably the Firefly Squid (also known as the Sparkling Enope Squid) which can create large light displays.