Bioluminescence of Ctenophore Pleurobrachia pileus (O. F. Müller, 1776) in the Summer Period

The ability to bioluminescence has been found in many marine hydrobionts, including almost all representatives of the Ctenophora phylum which have the ability to emit light. The luminescence of species and bioluminescent substrates isolated from them are actively used in biology, ecology and medicine to study the physiological state of the organism or to identify unfavorable environmental parameters. Parameters of luminescence of representatives of Black Sea ctenophores Mnemiopsis leidyi A. Agassiz, 1865 (Lobata) and Beroe ovata Bruguière, 1789 (Beroida) are used in the study of the effects of toxicants, such as liquid hydrocarbons, polychlorinated biphenyls, and heavy metals. The ability to bioluminescence of an autochthonous inhabitant of the Black Sea, the ctenophore Pleurobrachia pileus (O.F. Müller, 1776), was doubted by some researchers. The aim of this study was to confirm the ability of this species to glow and to choose the optimal time for conducting experiments with it. It was found that all size groups of this species exhibited a bioluminescent reaction to mechanical and chemical stimulation at any time of the day. With chemical stimulation, the bioluminescent signal energy values were several times higher than with mechanical stimulation. It was found that the optimal time for conducting biophysical studies is the period from 20:00 to 6:00, since the energy indicators of the bioluminescent signal at this time are maximum within a day.