Recent research by a Swedish scientist has shed more light on the way bioluminescence in marine organisms work (pun intended).
Jenny Krnstrm was recently awarded a PhD from the University of Gothenburg for her study of the light organs of marine jellyfish, crustaceans and fish (thesis title: Control of bioluminescence: Operating the light switch in photophores from marine animals). She found that luminescent krill possess special muscles that regulate light intensity through contraction and relaxation.
An important substance thought to play a role in luminescence in krill is nitric oxide.
This is produced in both the small capillary vessels that supply the krill's photocytes with oxygen, and in sphincters (closure muscles) where these capillaries distribute blood to the photocytes.
By manipulating the contraction and relaxation of these sphincters with chemical agents, Krnstrm showed that krill luminesce when the sphincters relax, presumably because of the increased flow of oxygenated blood to the photocytes.
Because bioluminescence has been independently evolved several times, different mechanisms of emitting and regulating light have developed in different species.
Krnstrm s research also demonstrated the differing effects of nitric oxide in different species, with nitric oxide inhibiting the light reaction in the Silver Hatchetfish (Argyropelecus olfersii), while stimulating it in the Plain Midshipman (Porichthys notatus).