Screening of second messengers involved in photocyte bioluminescence control of three ophiuroid species (Ophiuroidea: Echinodermata).

We investigated the effects of cyclic nucleotides (cGMP and cAMP) and inositol triphosphate/diacylglycerol pathways on the KCl-induced luminescence control of the ophiuroid species Amphiura filiformis, Ophiopsila aranea and Ophiopsila californica. Results show that dibutyrylcGMP, the cGMP analogue, and sodium nitroprusside, the guanylyl cyclase activator, had no effect on the luminescence of O. aranea and O. californica. On the other hand, cGMP could be involved in an inhibitory control in A. filiformis. Dibutyryl-cAMP, the cAMP analogue, and forskolin, the adenylyl cyclase activator, had no effect on maximal light emission, but the adenylyl cyclase inhibitors MDL-12,330A and SQ22,536 affected the kinetics of light production in both Ophiopsila species and strongly reduced KCl-induced luminescence in A. filiformis and O. aranea, suggesting cAMP pathway involvement in photogenesis. The phospholipase C inhibitor U-73122 also strongly reduced KCl-induced luminescence in all three species but this effect seems to be unspecific since U-73343, the inactive analogue of U-73122, equally inhibited photogenesis. Therefore, the results suggest that luminescence control of A. filiformis, O. aranea and O. californica is mediated by cAMP in synergy with calcium.