Carbamazepine increases marbled crayfish movement in laboratory exposure study

Marbled crayfish exposed to an environmentally relevant concentration of the anticonvulsant carbamazepine became more active in a laboratory study, nearly doubling the distance moved and increasing walking speed compared with a solvent control. The 96-hour experiment found no detectable behavioural changes in crayfish exposed to either diclofenac or diphenhydramine at the tested concentrations. The study examined whether pharmaceutical residues can alter behaviour in aquatic crustaceans.

Researchers exposed marbled crayfish, Procambarus virginalis , to one of three drugs at either an environmentally relevant concentration or a lowest observed effect concentration. Carbamazepine, a neutral compound, was tested at 11.6 and 116 micrograms per litre. Diclofenac, an ionisable weak acid, was tested at 31 and 310 micrograms per litre, while diphenhydramine, an ionisable weak base, was tested at 1.4 and 95 micrograms per litre.

The exposures took place under laboratory conditions in water with a pH of 7.6 and a temperature of 22 °C. The researchers assessed several movement-related behaviours, including the percentage of movement activity, distance travelled and walking speed, and compared each exposure group with a solvent control. Carbamazepine produced the clearest response. At 11.6 micrograms per litre, the concentration classified by the researchers as environmentally relevant, exposed crayfish showed a higher percentage of movement activity, nearly twice the distance moved and a higher walking speed than the solvent-control animals.

At the drug’s lowest observed effect concentration of 116 micrograms per litre, the only reported change was increased relative movement activity. The results therefore did not amount to an increase in every measured movement variable at both exposure levels. Neither diclofenac nor diphenhydramine was associated with detected behavioural changes under the tested conditions.

This null finding is limited to the concentrations, species and laboratory protocol used in the experiment; it does not demonstrate that the two drugs are incapable of affecting marbled crayfish behaviour. The study was also conducted in a controlled setting and therefore did not directly establish whether the observed responses occur in natural waterways. Nevertheless, its results show that pharmaceutical exposure can produce measurable changes in a movement-related trait at a concentration described as environmentally relevant, while also illustrating that the response depends on the specific compound and exposure level tested.

Subject of Research: Laboratory assessment of pharmaceutical-induced behavioural changes in marbled crayfish

Article Title: Behavioural impacts of ionisable and neutral pharmaceuticals on marbled crayfish (Procambarus virginalis)

Article References: Koubová, A., Thammatorn, W., Kubec, J., Nováková, P., Fedorova, G., Kouba, A., & Žlábek, V. (2026). Behavioural impacts of ionisable and neutral pharmaceuticals on marbled crayfish (Procambarus virginalis). Ecotoxicology, 35(9), 185. https://doi.org/10.1007/s10646-026-03166-w

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03166-w

Keywords: marbled crayfish, carbamazepine, diclofenac, diphenhydramine, behavioural toxicology, pharmaceutical residues, aquatic pollution, ecotoxicology, laboratory exposure, crustaceans, Behavioural, impacts