The behavioural, physiological and biochemical responses of Lumbriculus variegatus exposed to cannabidiol (CBD) and its metabolites.

Abstract

Cannabidiol (CBD) is a major non-psychoactive cannabinoid that has been detected in environmental samples, but the ecotoxicological effects remain unknown. In this study, Lumbriculus variegatus are exposed to CBD, and its metabolites 7-hydroxy-cannabidiol (7-OH-CBD) and 7-carboxy-cannabidiol (7-COOH-CBD). In this study, toxicity, tactile stimulation to elicit stereotypical behaviours and locomotor activity are measured after 24-hour exposure of L. variegatus to CBD and its metabolites. We also describe the impacts on dorsal blood vessel pulsation and oxygen consumption after 24-hour exposure to CBD and 7-OH-CBD, and the effects on regenerative capacity and total energy reserves after 72 hours of exposure to CBD and 7-OH-CBD. We observe CBD, 7-OH-CBD and 7-COOH-CBD display toxicity in 50% of test populations at 14.12 µM, 11.29 µM and 15.36 µM, respectively. 24-hour exposure to CBD decreases tactile stimulation response to elicit body reversal at ≥ 2.5 µM and helical swimming at ≥ 0.5 µM and reduces locomotor activity. L. variegatus oxygen consumption was not affected by CBD but ≥2.5 µM significantly reduced dorsal blood vessel pulse rate. We observe that exposure to 7-OH-CBD does not affect the regenerative capacity of L. variegatus while CBD is shown to reduce regeneration. Exposure to CBD also results in a significant decrease in carbohydrates, increased lipid, and no effect on protein levels in L. variegatus. We determined that CBD can reduce L. variegatus behaviours, decrease pulse rates and regenerative capacity, and disrupt energy reserves. Our findings show that CBD is toxic to this common aquatic organism and the increased availability and use of CBD, and related substances, warrants further study of their environmental impact.