Aquaculture Research. 2020;00:1–12. wileyonlinelibrary.com/journal/are | 1 © 2020 John Wiley & Sons Ltd 1 | INTRODUCTION Pacu (Piaractus mesopotamicus) is a highly prized neotropical characid (for meat and sport fishing) that has favourable zootech- nical characteristics such as resistance to diseases, good consumer acceptance and rapid growth in various growing conditions (Gelman et al., 2004; Jomori et al., 2003; Kuradomi et al., 2017; Mourad et al., 2018; Souza et al., 2003) and for these reasons it has out- standing commercial importance in the American continent and more recently across the world (Valladão et al., 2018). Pacu belongs Received: 13 August 2020 | Accepted: 9 October 2020 DOI: 10.1111/are.14957 ORIGINAL ARTICLE Resumption and progression of meiosis and circulating levels of steroids and prostaglandin F 2α of Piaractus mesopotamicus induced by hypophysation with prostaglandin F 2α Rafael Tomoda Sato 1 | Rafael Yutaka Kuradomi 2 | Marina Cabral Calil 1 | Laiza Maria de Jesus Silva 1 | Mariana Roza de Abreu 1 | Daniel Guimarães Figueiredo-Ariki 1 | Guilherme Antônio de Freitas 1 | Sergio Ricardo Batlouni 1 1 Aquaculture Center of São Paulo State University, CAUNESP, São Paulo State University–UNESP, Sao Paulo, Brazil 2 Institute of Exact Sciences and Technology- ICET, Federal University of Amazonas- UFAM, Itacoatiara, Brazil Correspondence Sergio Ricardo Batlouni, Aquaculture Center of São Paulo State University–CAUNESP, São Paulo State University–UNESP, Via de Acesso Prof. Paulo Donato Castellane, S/N, Jaboticabal, SP 14884-900, Brazil. Email: sergio.ricardo@unesp.br Funding information Fundação de Amparo à Pesquisa do Estado de São Paulo, Grant/Award Number: 2016/20741-3; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Grant/Award Number: master's scholarship Abstract We have previously shown an increase on the ovulation rate of pacu, Piaractus meso- potamicus, using hypophysation with prostaglandin F 2α (PGF 2α ) (HPG protocol) rather than hypophysation (H); only, however, a persistent lack of ovulation in some fe- males could not be further explained by PGF 2α and steroid plasma levels at time of ovulation. Considering this, here we compared the meiotic process and steroids and PGF 2α levels during spawning induction using both protocols. To that, H and HPG were treated with conventional hypophysation (0.6 mg/kg priming and 5.4 mg/kg re- solving dose), and the latter received synthetic PGF 2α (2 mL/fish) at resolving dose. A negative control (saline solution), a SPG group (receiving only PGF 2α ) and a PPG group (receiving priming and PGF 2α ) were included. An initial PGF 2α peak between one to four hours post-resolving dose (1-4 hr) occurred in groups receiving PGF 2α (HPG, SPG and PPG). Only H and HPG showed a 17α-20β-dihydroxy-4-pregnen-3-one (DHP) peak 4 hr, concomitant with meiosis resumption, and a final PGF 2α peak 12 hours. The HPG protocol resulted in higher PGF 2α plasma levels for longer periods (1-4 and 12 hr) than H (single peak 12 hr), occasioning in the former higher and concomitant levels of both PGF 2α and DHP at 4 h. Considering that DHP is known to induce ex- pression of prostaglandin receptors in fish, the concomitant plasma peaks of DHP and PGF 2α may also explain the ovulation rate gain previously published, using HPG protocol, which can be further improved adjusting the priming dose and defining the exact interval of PGF 2α ovulatory action in this species. KEYWORDS DHP, hormonal induction, plasma profile, priming dose, prostaglandin