Alteration of predatory behaviour and growth in juvenile cuttlefish by fluoxetine and venlafaxine

Abstract

Antidepressants in coastal waters may affect ontogeny of predatory behaviour in cuttlefish, which may, as a result, affect growth of newly-hatched cuttlefish. We investigated the effects of two of the most prescribed antidepressants, fluoxetine (FLX) and venlafaxine (VEN) in environmentally realistic concentrations on the predatory behaviour of hatchlings of Sepia officinalis. Newly-hatched cuttlefish were exposed from 1 h (i.e., day 1) to 5 days after hatching to either FLX alone (5 ng·L−1) or combined with VEN (2.5 ng·L−1 or 5 ng·L−1 each) to simulate an environmentally realistic exposure scenario. Their predatory behaviour was analysed through several parameters: prey detection, feeding motivation and success in catching the prey. All parameters improved in control animals over the first five days. The combination of FLX and VEN at 5 ng·L−1 each altered the predatory behaviour of the hatchlings by increasing the latency before attacking the prey, i.e., reducing feeding motivation, as well as by reducing the number of successful attacks. The changes in predatory behaviour tended to reduce food intake and affected growth significantly at 28 days post-hatching. Exposures to either FLX at 5 ng·L−1 or FLX and VEN in mixture at 2.5 ng·L−1 each tended to produce similar effects, even though they were not statistically significant. It is likely that the antidepressants affect maturation of the predatory behaviour and/or learning processes associated with the development of this behaviour. The slightest delay in maturation processes may have detrimental consequences for growth and population fitness.