BIOLUMINESCENCE OF THE AUSTRALIAN GLOW‐WORM, ARACHNOCAMPA RICHARDSAE HARRISON

Abstract

Abstract— Stable dry powders of the light organ of the glow‐worm, Arachnocampa richardsae (Diptera) have been prepared and although the amounts of material are extremely limited, a semi‐quantitative description of the bioluminescence reaction can be given. The in vivo and in vitro bioluminescence spectra are the same, maximum 488 nm (corrected) and the shape of the in vitro emission spectrum is not influenced by pH (5.9–8.5). Light is produced by addition of buffer (optimum pH 7) to the powder, but is stimulated several fold if the buffer contains adenosine 5'‐triphosphate (ATP), about 0.3 mM being required for half maximum stimulation. A number of other high‐energy phosphates do not stimulate. Ethylenediaminetetraacetate quenches the ATP stimulation implicating a Mg2+ requirement, but not ethylene‐bis(oxyethylene‐nitrilo)‐tetraacetate which chelates Ca2+ but not Mg2+. Inorganic pyrophosphate (2 mM) also quenches if added with the ATP but in contrast to the firefly (Coleoptera) reaction, does not stimulate the light emission if added post‐ATP. The decay of the ATP‐stimulated glow‐worm bioluminescence is first‐order unlike the strongly product inhibited firefly kinetics. Oxygen is required for both in vivo and in vitro bioluminescence. A glow‐worm can emit more than 1015 photons in its lifetime but at any one time, appears to possess only about 10% of this total capacity.