Bioluminescence of ctenophore Pleurobrachia pileus (O.F. Muller, 1776) in the summer period

The capability of bioluminescence has been found in many marine hydrobionts, including almost all representatives of the phylum Ctenophora. The glow of species and bioluminescent substrates isolated from them is actively used in biology, ecology, and medicine to study the physiological state of an organism or to identify unfavorable environmental parameters. The parameters of luminescence of the Black Sea ctenophores Mne-miopsis leidyi A. Agassiz, 1865 (Lobata) and Berce ovata Bruguicre, 1789 (Beroida) are used to study the effects of toxicants, such as liquid hydrocarbons, PCBs, and heavy metals. Some researchers casted doubt on the capability of the Black Sea autochthonous inhabitant, ctenophore Pleurobrachia pileus (O. F Muller, 1776) to produce bioluminescent light. The objective of this work was to ensure scientific support for the light-producing ability of species under study and to choose the optimal time for conducting experiments on the factors that affect bioluminescence. It was found that mechanical and chemical stimulation triggered a bioluminescent response in all size groups of species under study at any time of day. Upon chemical stimulation of the studied species, the signal energy value was several times greater than that observed after mechanical stimulation. It was revealed that the optimal time interval for conducting biophysical research is the time from 8 pm to 6 am, because the values of luminescence activity are the greatest in this time interval within a day.