In a number of marine organisms, for example fishes and squids, luminous bacteria produce bioluminescence. This process however does not occur within crustaceans, unless temporarily infected by the bacteria (Giard, 1889). Instead, members of Euphausiidae have complex photophores (light emitting organs) (Figure 3). These do not produce a secretory luminescence. The photophores are located on each eyestalk, anterior and posterior thorax, and on the first four abdominal segments (Herring, 1985). The bioluminescence used by the krill is a vivid blue-green colour and is thought to be used in communication to help with congregation and spawning (Marinebio, 2013).

Figure 1: Antarctic krill displaying luminescent properties
Figure 3: Antarctic krill displaying luminescent properties