lanternfish

Lanternfish are small, bioluminescent fish of the family Myctophidae. Found throughout the world's oceans, they are especially common in the mesopelagic zone between about 200 and 1000 meters. Lanternfish are among the most abundant vertebrates on the planet, and together comprise a substantial portion of the deep-sea fish biomass. They are characterized by numerous photophores—light-emitting organs—arranged in species-specific patterns along the head, trunk, and fins, used for camouflage, species recognition, and signaling.

Most lanternfish are small, typically 2 to 15 cm long. They inhabit open water rather than reefs and form large schools. They undertake daily vertical migrations: by day they dwell in deeper, darker waters; at dusk they move upward to shallower depths to feed on zooplankton such as copepods and krill, then return to depth before dawn.

Reproduction is generally pelagic. Lanternfish reproduce through external fertilization, and eggs and larvae are planktonic. Individuals may exhibit species-specific photophore patterns that assist in mate recognition. The bioluminescence not only aids camouflage via counterillumination but also enables communication in the dimly lit deep sea.

Ecologically, lanternfish are a critical trophic link between the mesopelagic and epipelagic zones, serving as prey for larger fish, seals, penguins, and whales. Their migrations contribute to the ocean's carbon cycle by transporting surface-produced carbon to deeper waters and through fecal pellet production, a component of the biological carbon pump.