LUMINESCENCE CONTROL IN PORICHTHYS (TELEOSTEI): EXCITATION OF ISOLATED PHOTOPHORES

¹ Université de Louvain, Louvain, Belgium
² Université of California, Santa Barbara, California; and the Marine Biological Laboratory, Woods Hole, Massachusetts

Luminescene of isolated photophores of midshipman fish, Porichthys myriaster and P. notatus, was studied as a function of electrical stimulus characteristics, temperature, oxygen concentration and pH. Single stimuli delivered into the photophore via microelectrode induced luminescence with a minimum latency of 100 msec. Externally applied stimuli were ineffective at rates of less than 2/sec and at 5/sec latency was between 5 and 19 seconds. These values suggest the possibility of both direct and indirect photophore excitability. Oxygen is essential for luminescence, but spontaneous occurrence of luminescence after electrical stimulation under nitrogen suggests that certain elements of the excitation-luminescence sequence are relatively insensitive to anaerobiosis. The temperature optimum is at about 20° C and the Q₁₀ is 4.5. Total light produced was greater at pH 7.4 than at 5.6. Maximal light production is estimated at 1.4 x 10^-3 microwatt per photophore.