Many (but not all) of the bioluminescent systems in coelenterates involve energy transfer from an excited product molecule of the calcium activated photoprotein to a second species, the green fluorescent protein, with emission at 508 nm from its excited state. Although all the luminescent coelenterates studied possess photoproteins, not all of them have the green fluorescent protein. This green fluorescent molecule is localized in the luminescent cells; they can thus be easily distinguished by fluorescence microscopy. The active components occur in subcellular particles; these have been isolated in an active form by homogenization in isotonic (to sea water) salt solutions.

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SUMMARYIn the western Caribbean Sea, about an hour after the sun sets, a complex and ritualized light show of precise, vertically placed luminescent pulses erupts over shallow grassbeds. These are among the most complex displays known in marine systems. Displays consist of repeated trains of secreted bioluminescent pulses in a specific pattern ejected into the water column as courtship signals by male Vargula annecohenae, which are small (<2 mm) myodocopid ostracod crustaceans. Although these animals display in near darkness, we have used image intensification and infrared videography and three-dimensional analysis in the lab to demonstrate that each luminescent display train, which can be up to 60 cm long, consists of two distinct luminescent and swimming phases. The first, or 'stationary,' phase consists of three (usually) bright, longer pulses placed close together, with the male swimming in a looping pattern. We hypothesize that this pattern acts as an attention-grabbing signal for receptive females. The stationary phase is followed by the 'helical phase,' which consists of about a dozen evenly placed dimmer, shorter pulses secreted by an individual male rapidly spiraling upward in a helical pattern. We hypothesize that this phase, which has very uniform interpulse intervals and distances, helps an approaching female target and intercept the rapidly moving male. Here we provide details of these two phases, and produce a three-dimensional model of a multiply-displaying male.

The flashlight fish, Photoblepharon , possesses headlight-like luminous organs situated in the orbit just below the eyes. On the basis of direct field and laboratory studies, it is postulated that the bioluminescence is used by the fish for many different functions: to assist in obtaining prey, to deter or escape predators, and for intraspecific communication. The fish also uses its light to see by.