Along the Pacific coast of North America, the marine fish, Porichthys notatus, is distributed as a northern nonluminescent population and a southern luminescent one. Bioluminescence capability is inducible in nonluminescent P. notatus by a single oral or intraperitoneal administration of a small amount of luciferin, a compound used by the marine ostracod crustacean, Vargula, as substrate for light emission. Once induced, the fish is capable of luminescing for more than 2 years. The results of the present study show that: (1) P. notatus photophores incorporate 14C-labelled Vargula luciferin: (2) the specific activity of the incorporated label is undiluted when recovered from the photophores 7 weeks later; (3) two chemical analogues of Vargula luciferin do not induce bioluminescence capability in the fish; (4) luciferinol, another close analogue of Vargula luciferin, induces a very weak bioluminescent capability in the fish; and (5) two key intermediates in the degradation of Vargula luciferin, oxyluciferin and etioluciferin, are ineffective in inducing bioluminescence capability. The conclusions to be drawn from this study are that P. notatus recycles luciferin and that, in the uninduced fish, the recycling does not involve the resynthesis of luciferin from oxyluciferin or etioluciferin.

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