Luminescent activity and ultrastructural characterization of photocytes dissociated from the coelenterate Renilla köllikeri.

Dissociation and Percoll sedimentation techniques were used to separate and pool the autofluorescent luminescent cells (photocytes) of the pennatulid anthozoan Renilla köllikeri. Photometric recordings of luminescent activity of photocyte suspensions show that activation of flashing and glowing by KCl depolarization is suppressed in calcium-free sea water and by cobalt but enhanced by trifluoperazine, thus suggesting that luminescence excitation is dependent on extracellular calcium and calmodulin-mediated mechanisms. Of several neuroactive substances tested, adrenaline, dopamine, N-methyl-N-phenylethanolamine, serotonin and the native neuropeptide Antho-RFamide all induced photocyte responses at high concentrations (0.1-1 mM) only, whereas lower concentrations of adrenaline and Antho-RFamide are known to activate or enhance luminescence or muscular contractions in intact Renilla tissues (Anctil et al., 1982; Anctil, 1987). Hence, none of these substances is a likely neurotransmitter candidate for direct photocyte activation. Ultrastructural observations of dissociated photocytes reveal that they are musculo-epithelial cells containing numerous 0.2-mum vesicles resembling previously extracted and light-emitting lumisomes (Anderson and Cormier, 1973). Similar cells were traced ultrastructurally in situ in the endodermal luminescent zones, but not in non-luminescent endoderm.