Zooxanthellin

Zooxanthellin is a class of carotenoid pigments found in symbiotic dinoflagellates, commonly known as zooxanthellae. These dinoflagellates live within the tissues of various marine invertebrates, most notably corals, but also in some anemones, jellyfish, and giant clams. Zooxanthellin, along with other pigments like chlorophylls, plays a crucial role in the symbiotic relationship.

The primary function of zooxanthellin is to absorb light energy. While chlorophylls are the main photosynthetic pigments, zooxanthellin acts as an accessory pigment, broadening the range of light wavelengths that can be captured for photosynthesis. This is particularly important in shallow, sunlit waters where corals live. The absorbed light energy is then transferred to chlorophylls, where it is used to drive the photosynthetic process.

Through photosynthesis, the zooxanthellae produce organic compounds such as glucose and amino acids. These compounds are then transferred to their host invertebrate, providing a significant source of nutrition. In return, the host provides the zooxanthellae with a protected environment and the inorganic nutrients they need for growth and photosynthesis, such as carbon dioxide and nitrogenous waste. The vibrant colors of many corals are also attributed to the pigments within their zooxanthellae, including zooxanthellin. When corals are stressed, such as by rising ocean temperatures, they can expel their zooxanthellae, leading to coral bleaching and a loss of color.