Neuropeptide F stimulates ovarian development and spawning in the female giant freshwater prawn, Macrobrachium rosenbergii, and its expression in the ovary during ovarian maturation cycle

Abstract

© 2016 Elsevier B.V. Neuropeptide F (NPF) plays important roles in the regulation of a variety of physiological processes, including stimulation of food intake. At present, there is a current lack of basic knowledge regarding the effect of NPF in the control of female crustacean reproduction. In this study, we investigated expression of NPF in ovaries of female Macrobrachium rosenbergii (Mr) during ovarian development cycle, and its effects on ovarian maturation and spawning. MrNPF-immunoreactivity (-ir) was detected in the ovaries and its levels fluctuated during the ovarian maturation cycle: MrNPF-ir was more intense in the early- and mid-stages of ovarian development, and suddenly decreased in the mature stages. By RT-PCR, MrNPF transcript levels also increased during the early- and middle stages of ovarian development, and suddenly fell at late stage. The prawns were treated with varied doses of MrNPF and the effects were investigated by assessing the ovarian maturation period, oocyte diameter (OD), gonado-somatic index (GSI), and hemolymph vitellogenin (Vg) concentration. MrNPF-treated prawns showed significantly decreased ovarian maturation periods, and increased GSI, OD, and Vg levels compared with those of control groups. MrNPF also caused significantly earlier spawning compared with the control groups, while the mean fecundity between MrNPF-treated prawns and controls did not differ significantly. However, the numbers of eggs per spawn among experimental groups were higher compared with those of the controls. This work provides a novel and useful basic knowledge of NPF on female reproduction in crustaceans, and its possible use in aquaculture for accelerating and enhancing reproduction of the female prawns. Statement of relevance Alternative techniques to eyestalk ablation to stimulate ovarian maturation in captive prawn broodstock are needed in order to avoid cruel practice on cultured prawns. Attempts have been made in using neurohormones, including neuropeptides to prime female broodstocks to stimulate growth and reproduction to replace the eyestalk ablation. NPF is a neuropeptide known for its control of feeding; however, there is currently no report on the role of NPF in female M. rosenbergii reproduction. We are the first to report the effects of NPF on ovarian maturation and spawning, and its expression and fluctuation in ovaries during the ovarian cycle in the female decapod crustacean. Our findings are novel and the data obtained could be useful for accelerating and enhancing reproduction of the female freshwater prawns.