BIOLUMINESCENCE OF MYCTOPHID AND STOMIIFORM FISHES IS NOT DUE TO BACTERIAL LUCIFERASE

A recent report by D. Foran proposes that bioluminescence of myctophid s and some stomiiform fishes is due to bacterial symbionts in their ph otophores, based on positive hybridization of bacterial luminescence ( lux) gene probes to DNA from muscle and skin of myctophids and stomiif orms and in situ hybridization. Previous microscopic studies have not revealed the presence of bacteria in these fishes, and bioluminescence of myctophids has been attributed to a coelenterazine-based system. W e have investigated this finding by assay of bacterial luciferase and by lux hybridization to DNA from photophores and control samples in or der to determine whether bacterial symbionts or bacterial lux genes ar e present in these fishes. Results of enzyme assays of photophores fro m six species of myctophids and two species of stomiiforms show bacter ial luciferase activity ranging from 0 to 7 x 10(5) quanta sec(-1) mg wet weight(-1). The highest levels detected were 3-4 orders of magnitu de less than the activity of luminous bacteria and symbiotic light org an extracts, and were less than or equal to the activity of gut homoge nates, which were up to tenfold higher than the highest photophore act ivities. Hybridization with lux probes did not detect lux sequences in photophore DNA from three species of myctophids and three species of stomiiforms. We find no evidence that bacterial luciferase is the sour ce of luminescence in myctophid and stomiiform light organs. (C) 1994 Wiley-Liss, Inc.