Metabolism of the aquatic pollutant diclofenac in the Lymnaea stagnalis freshwater gastropod

The metabolism of organic contaminants in Lymnaea stagnalis freshwater gastropod remains unknown. Yet, pharmaceuticals-like the NSAID diclofenac-are continuously released in the aquatic environment, thereby representing a risk to aquatic organisms. In addition, lower invertebrates may be affected by this pollution since they are likely to bioaccumulate contaminants. The metabolism of pharmaceuticals in L. stagnalis requires further investigation to understand their detoxification mechanisms and characterized the risk posed by contaminant exposure in this species. In this study, a non-targeted strategy using liquid chromatography combined with high-resolution mass spectrometry was applied to highlight metabolites formed in L. stagnalis freshwater snails exposed to 300 µg/L diclofenac for 3 and 7 days. Nineteen metabolites were revealed by this approach, 12 of which were observed for the first time in an aquatic organism exposed to diclofenac. Phase I metabolism involved hydroxylation, with detection of 3'-, 4'-, and 5-hydroxydiclofenac and three dihydroxylated metabolites, as well as cyclization, oxidative decarboxylation, and dehydrogenation, while phase II metabolism consisted of glucose and sulfate conjugation. Among these reactions, the two main DCF detoxification pathways detected in L. stagnalis were hydroxylation (phase I) and glucosidation (phase II).

Multigenerational responses in the Lymnaea stagnalis freshwater gastropod exposed to diclofenac at environmental concentrations

Over the last decade, there has been increased concern about the occurrence of diclofenac (DCF) in aquatic ecosystems. Living organisms could be exposed to this "pseudo-persistent" pharmaceutical for more than one generation. In this multigenerational study, we assessed the DCF impact at environmentally relevant concentrations on the life history and behavioral parameters of two offspring generations (F1 and F2) of the Lymnaea stagnalis freshwater gastropod. Snail growth was affected by DCF in the F1 generation, with increased shell sizes of juveniles exposed to 0.1 µg L ^- 1 concentration and a decreased shell size at 2 and 10 µg L ^- 1. DCF also lowered food intake, enhanced locomotion activity and reduced the number of eggs/egg mass in the F1 generation. For the F2 generation, shorter time to hatch, faster growth, increased food intake and production of more egg masses/snail were induced by DCF exposure at 10 µg L ^- 1. Over time, DCF exposure led to maximization of L. stagnalis reproductive function. These results show that multigenerational studies are crucial to reveal adaptive responses to chronic contaminant exposure, which are not observable after short-term exposure.

Long-term exposure to environmental diclofenac concentrations impairs growth and induces molecular changes in Lymnaea stagnalis freshwater snails

As pharmaceutical substances are highly used in human and veterinary medicine and subsequently released in the environment, they represent emerging contaminants in the aquatic compartment. Diclofenac (DCF) is one of the most commonly detected pharmaceuticals in water and little research has been focused on its long-term effects on freshwater invertebrates. In this study, we assessed the chronic impacts of DCF on the freshwater gastropod Lymnaea stagnalis using life history, behavioral and molecular approaches. These organisms were exposed from the embryo to the adult stage to three environmentally relevant DCF concentrations (0.1, 2 and 10 μg/L). The results indicated that DCF impaired shell growth and feeding behavior at the juvenile stage, yet no impacts on hatching, locomotion and response to light stress were noted. The molecular findings (metabolomics and transcriptomic) suggested that DCF may disturb the immune system, energy metabolism, osmoregulation and redox balance. In addition, prostaglandin synthesis could potentially be inhibited by DCF exposure. The molecular findings revealed signs of reproduction impairment but this trend was not confirmed by the physiological tests. Combined omics tools provided complementary information and enabled us to gain further insight into DCF effects in freshwater organisms.