The effects of serotonin and spiperone on sperm count during successive spermatophore extrusions in the whiteleg shrimp, Litopenaeus vannamei

This work aimed to evaluate the effects of serotonin and spiperone application on spermatophore and sperm quality and the relative expression of genes related to oxidative stress in Litopenaeus vannamei subjected to successive spermatophore extrusions. Sixty males were randomly divided into three experimental groups: a control that received no injections; a vehicle control (VHC), injected with a saline solution and ethanol mixture (as a vehicle for serotonin and spiperone) to account for the effects of handling and injections; and the combined serotonin and spiperone treatment (5-HT-SPY), injected with 25 μg/g body weight (b.w.) of 5-HT and 5 μg/g b.w. of SPY every two weeks. The shrimp were maintained under controlled conditions, including regulated temperature, photoperiod, and ad libitum feeding. Spermatophore and sperm quality parameters, including sperm count, spermatophore weight, spermatosomatic index, melanization, and sperm mortality, were measured across five spermatophore extrusions. Oxidative stress was assessed through the relative expression of antioxidant genes in the hepatopancreas. The results revealed a significant increase in sperm count in the 5-HT-SPY by the fourth spermatophore regeneration, while spermatophore weight, sperm mortality, and melanization showed no statistical differences among treatments. Additionally, no significant differences in oxidative stress markers were observed among the groups, suggesting that neither the serotonin and spiperone injections nor the control conditions disrupted the shrimp's ability to maintain physiological homeostasis. These findings suggest that 5-HT-SPY may enhance spermatozoa production in L. vannamei without disrupting physiological homeostasis. • Serotonin and spiperone increased sperm count in Penaeus vannamei . • There was no effect on spermatophore weight, sperm mortality, or melanization. • Antioxidant gene expression showed no disruption of oxidative stress balance. • Sperm production was enhanced without impairing physiological homeostasis. • Neurotransmitter modulation may improve shrimp reproductive performance.