Effects of different visible light spectrums on phototaxis and bottom preference behavior of sea cucumber

Abstract

In recent years, studies have shown that different light wavelengths have varying effects on aquaculture species. This indicates that exposure to light can significantly influence the health and development of aquatic organisms. This study investigated the effects of different visible light spectra on the behavior and physiological responses of sea cucumbers. Under blue LED and white LED illumination, the sea cucumbers exhibited shelter-seeking behavior. A phototaxis experiment found that the blue LED light elicited the strongest negative phototaxis, followed by the white LED. However, the red LED light elicited no obvious response. In the bottom zone preference experiment, blue LED and white LED illumination affected the bottom preference behaviors of some individuals compared to the control group. By measuring the mean photon flux density (MPFD) values at different illumination distances, the individuals in each group tended to stop moving when they were close to a similar MPFD value. Next, this study examined the physiological effects of red LED and blue LED illumination on sea cucumbers. Interestingly, the blue LED group exhibited higher oxygen consumption rates and thinner connective tissue in the respiratory tree during the early stage of the experiment. In contrast, no significant differences in coelomocyte phagocytosis were observed between the blue LED and red LED groups. Our findings suggested that the behaviors and physiological responses elicited by the blue or white LED light are likely caused by the number of photons in a specific time and area received by photoreceptors on the integument of sea cucumbers. Furthermore, neither long- nor short-wavelength spectra caused significant stress or damage to sea cucumbers in this study. The results obtained from this data will be beneficial for lighting usage in aquaculture environments in the future.