They shine at night - in the air, on the ground, or in the sea. These little gleaming creatures in the natural world captivate people in the dark. But they do not shine to enchant you, but so that they can survive.
Animals' glows are used for communication, mating, feeding and fending off enemies. There are a variety of ways to glow. Some contain in their bodies glowing materials such as luciferin and luciferase; when the former is catalysed by the latter, it is turned into an unstable oxide which then releases light. This is the way fireflies and Cypridina glow.
Jellyfish, on the other hand, contain other special materials - aequorin and green fluorescent protein (GFP). Aequorin emits blue light, which is then absorbed by GFP to produce the green glowing light of jellyfish.
Some animals do not manufacture their own glowing materials but rely on others that glow. Angler Fish, for example, has a light organ on its head which contains light-producing bacteria. These bacteria make luciferin and undergo photosynthesis, while Angler Fish makes use of the light to attract prey.
Blue Rays: The Ocean's Tears
To date, people have discovered numerous animals that can glow, including: insects (e.g. fireflies), fish, molluscs (e.g. jellyfish, octopus), algae, fungi and bacteria. Several of these creatures can be found in Hong Kong. The most familiar are the fireflies, of which there are 27 species locally. On hot summer nights, they emit light from their “light organ”, which is filled with luciferin and luciferase. Fireflies can regulate the lighting frequency through the nerve signal, to generate special “love messages” for mating. The light is also used to locate members of the opposite sex. Apart from mating, the glowing light is used as an alert against their natural enemies.
Sea Sparkle (Noctiluca scintillans) is another common glowing creature in Hong Kong. When disturbed, these algae floating on the sea emit bright blue light. The magnificent scene of a blue sea at night is nicknamed "Blue Tears". The glowing light attracts stronger predators that can chase away invaders. As beautiful as Sea Sparkle (Noctiluca scintillans) is, its appearance in large scale is worrisome, as it is an indication of water pollution, and red tides are created that can affect other marine life. There is another glowing fungi in Hong Kong - luminous mushroom, which resembles elegant green umbrellas, glowing amidst the darkened forest floor.