How do photophores produce light in squids and cuttlefishes?

In squids and cuttlefishes, photophores produce light through two primary methods:

• Internal Biochemical Reaction: Many squids generate light internally through an enzymatic reaction. In this process, the substrate luciferin is oxidized in the presence of the enzyme luciferase, converting chemical energy directly into light. These complex organs often include additional structures such as lenses, reflectors, diaphragms, and color filters to direct and modify the light.1234
• Symbiotic Bacteria: Some species, such as bottle-tailed squids, produce light indirectly by harboring cultures of luminescent bacteria within their light organs. These organs are typically supplied with blood to nourish the bacteria, and the host can control the light output using mechanisms like pigment-filled cells or shutters.23

These light-producing capabilities serve various essential functions, including defense, camouflage, attracting prey, and signaling for mating or species recognition.253