RESEARCH ARTICLE New insights into the spermatogenesis of the black tiger prawn, Penaeus monodon Tianyi Feng 1 | Brian Paterson 2 | Stephen Johnston 1 1 School of Agriculture and Food Science, University of Queensland, Gatton, Queensland 4343, Australia 2 Queensland Department of Agriculture and Fisheries, Bribie Island Research Centre, Woorim, Queensland 4507, Australia Correspondence Tianyi Feng, School of Agriculture and Food Science, University of Queensland, Gatton, Queensland 4343, Australia. Email: t.feng@uq.edu.au Abstract This study reports a comprehensive description of penaeid spermatogenesis (Penaeus monodon) by light and transmission electron microscopy. A conspicuous characteristic of spermatocytogenesis was a ring-like structure with high electron-density adjacent to the nucleus of a primary spermato- cyte. During the spermiogenesis from stage I (StI) to stage VI spermatid (StVI), the formation of the acrosome and decondensation of the nucleus were the most notable morphological transfor- mations. StIs were small and compact and they were contained in the syncytia. In the cytoplasm of StII, mitochondrion-like bodies (MLB) participated the extension of perinuclear multi-layered lamellae. The association of MLBs and endoplasmic reticula appeared to contribute to the forma- tion of small cytoplasmic pre-acrosomal vesicles (PV) which coalesced into an acrosomal chamber (AC) at the periphery of StIII. A dense anterior acrosomal body (AB) was formed in the enlarged AC in StIV. The nuclear envelope became disintegrated in StV. At last, an AB-derived spiky acro- some was emerged from AC in StVI. Sperm nuclei became increasingly decondensed during the entire process of spermiogenesis and the nuclear components in the testicular spermatozoa appeared to only contain chains of DNA and nucleosome-contained chromatin. KEYWORDS decapod crustacean, penaeid, shrimp, sperm production, transmission electron microscopy 1 | INTRODUCTION Male reproductive performance of captive penaeid prawns is consid- ered one of the major obstacles for the development of the prawn aquaculture industry and should therefore be given greater attention (Alfaro-Montoya, 2010). However, the current knowledge on male reproductive biology of penaeid species was either insufficient or out of date. Bell (1988) previously described the gross histology of sperma- togenesis for penaeid prawn Litopenaeus stylirostris, and other studies of spermatogenesis have only been conducted in a few penaeid prawns such as Litopenaeus schmitti (Fransozo, Fernandes, Lopez-Greco, Zara, & Santos, 2016), Fenneropenaeus chinensis (Kang, Ge, Guo, Liu, & Mu 2008), and Parapenaeus longirostris (Medina, 1994). Although Hong, Li, Guo, Ni, Huang, and Zhou (1998) and Chong et al. (2015) observed spermatogenesis of Penaeus monodon, the results of those studies were too brief and vague. A thorough understanding of sperm and spermatophore production is fundamental for the assessments and improvements in the reproductive performance of the male black tiger prawn, P. monodon and other penaeid prawns. This study describes the spermatogenesis of P. monodon in a more comprehensive way. 2 | MATERIALS AND METHODS 2.1 | Sample preparation Ten sexually mature male Penaeus monodon Fabricius, 1798 showing no melanization in the gonopores were euthanized in an ice water slurry for 10 min (Thompson, Gregory, Plummer, Shields, & Rowley, 2010) and their reproductive organs were dissected out. The left side of the reproductive organ was fixed in Davidson’s solution (1 L con- tains 220 ml 37–40% formaldehyde, 330 ml 95–100% ethanol, 115 ml glacial acetic acid, 335 ml distilled water, pH 3.5–4.0) for 24 hr at room temperature and then transferred to a 70% ethanol solution (Chong et al., 2015) for histological study, whereas the right side was preserved in the crustacean reproductive fixative (2% paraformaldehyde, 2.5% glutaraldehyde in 0.1 mol l 21 sodium cacodylate with 5% sucrose, pH Journal of Morphology. 2017;00–00 wileyonlinelibrary.com/journal/jmor V C 2017 Wiley Periodicals, Inc. | 1 Received: 1 November 2016 | Revised: 5 January 2017 | Accepted: 15 January 2017 DOI 10.1002/jmor.20664