Abstract
The selective serotonin reuptake inhibitors (SSRIs) fluoxetine (Nodep) and fluvoxamine (Dumyrox) are drugs commonly prescribed for the treatment of depression in humans. They act to increase serotonin (5-hydroxytryptamine) neurotransmission by inhibiting reuptake transport proteins at synapses. A similar effect of SSRIs seems to occur naturally in one group of invertebrates, the molluscs. In this study the action of these drugs at different concentrations and under different conditions was tested in the freshwater mussel Anodonta cygnea. Fluoxetine was more potent than fluvoxamine, inducing an intense release of larvae (parturition) at a concentration of 1 × 10–6 M in the presence of light. The non-SSRI antidepressants trazodone (Triticum), mianserine (Tolvon), and L-5-hydroxytryptophan (Cincofarm), which are known to have different serotoninergic mechanisms, had a strong, no, and a weak effect, respectively, on larval parturiton in A. cygnea. These effects suggest that serotonin could be a normal and relevant mediator of larval parturition in A. cygnea. Other parallel visible signs due to incubation with SSRIs were an increase in the volume of the foot and gills through water uptake and stimulation of valve movements. These results indicate that incubation with SSRIs is potentially important in culturing the larvae of freshwater bivalves, since it facilitates control of the intensity and timing of larval parturition.