Effects of serotonin (5‐HT) on juvenile culture of narrow‐clawed crayfish Pontastacus leptodactylus (Eschscholtz, 1823)

Serotonin was used for the first time in this study as a feed additive in juvenile freshwater crayfish Pontastacus leptodactylus, (stage II-V) to investigate its effects on growth performance, survival and immune response based on total haemocyte count (THC). Serotonin was included in diets at levels of 0 (control), 5, 10, 20 and 40 mg kg−1. When the results were examined, a significant quadratic increase was observed in the values of final total length: FTL and final body weight: FBW, weight gain (WG), length gain (LG) and specific growth rate (SGR) with dietary serotonin amounts (Plinear and Pquadratic <0.05). The survival rates of crayfish showed a significant linear increase with doses of serotonin (Plinear = 0.001). THC values, on the other hand, were not affected by serotonin amounts in experimental diets. The broken line models estimated optimum dietary serotonin inclusions based on FBW and FTL as 20.03 and 20.44 mg kg−1, respectively. In conclusion, dietary serotonin can be used in growing juvenile P. leptodactylus during the developmental stages of II-V.