Jellyfish captivate observers with their shifting hues and radiant glows. While these creatures do not change their inherent body color through pigment dispersal, they exhibit remarkable visual phenomena. These displays create the appearance of color changes, hinting at complex biological processes within their translucent bodies.
How Jellyfish Display Color and Light
Jellyfish display light and color through several distinct mechanisms. One prominent method is bioluminescence, the production of light through a chemical reaction within a living organism. In many jellyfish, this involves a light-emitting molecule, luciferin, reacting with oxygen in the presence of an enzyme called luciferase, or a photoprotein. For instance, the crystal jelly, Aequorea victoria, uses a photoprotein called aequorin which, upon binding with calcium ions, produces blue light. This blue light is then often absorbed by Green Fluorescent Protein (GFP), which re-emits the energy as green light.
Another mechanism is fluorescence, where jellyfish absorb light at one wavelength and then re-emit it at a different, longer wavelength. This means the jellyfish transforms ambient light, often appearing to glow under certain conditions like ultraviolet light. This phenomenon creates vibrant colors when external light sources interact with their tissues.
Jellyfish can also exhibit iridescence, a structural color that results from the scattering and interference of light off microscopic structures on their bodies. This effect causes colors to appear to shift and shimmer with changes in the viewing angle. While some jellyfish do possess fixed pigments that give them a consistent color, this is a static coloration and not a dynamic change. Their diet, age, and even symbiotic relationships with algae can influence these fixed colors over time.
The Purpose Behind Their Dazzling Displays
The diverse light and color displays in jellyfish serve various biological purposes, often linked to their survival and interaction within marine ecosystems. A primary function of bioluminescence is predator avoidance. Flashes of light can startle potential threats, giving the jellyfish a chance to escape. Some species employ a “burglar alarm” strategy, emitting light when attacked to attract larger predators, which may then target the initial attacker. Light can also serve as a form of camouflage in the deep ocean, where creatures use counter-illumination to match the faint light from above, making their silhouettes less visible to predators below.
Beyond defense, light displays can also aid in attracting prey. Some deep-sea jellyfish utilize glowing lures to draw in smaller organisms. For example, certain siphonophores, related to jellyfish, use glowing red tentilla to mimic shrimp and attract fish. This deceptive strategy allows them to capture food in environments where prey might be scarce.
While less common than in some other marine animals, light and color may play a role in communication or mating for certain jellyfish species. The ability to produce specific light patterns could potentially signal presence or readiness to other individuals. Additionally, these visual traits can be tied to environmental adaptation, with light production or reflection being advantageous in specific habitats, such as the perpetually dark deep sea where light is otherwise absent.