Acta Zoologica. 2018;1–12. wileyonlinelibrary.com/journal/azo | 1 © 2018 The Royal Swedish Academy of Sciences Received: 5 June 2018 | Revised: 19 July 2018 | Accepted: 9 August 2018 DOI: 10.1111/azo.12273 ORIGINAL ARTICLE Ultrastructure of spermatozoa of members of Calappidae, Aethridae and Menippidae and discussion of their phylogenetic placement Tavani Rocha Camargo 1 | Milena Regina Wolf 2 | Fernando L. Mantelatto 3 | Christopher Tudge 4,5 | Fernando José Zara 1 1 Laboratório de Morfologia de Invertebrados (IML), Departamento de Biologia Aplicada, UNESP Aquaculture Center (CAUNESP) and IEAMar, FCAV, Universidade Estadual Paulista (UNESP), Jaboticabal, São Paulo, Brasil 2 Departamento de Zoologia, Núcleo de Estudos em Biologia, Ecologia e Cultivo de Crustáceos (NEBECC), Instituto de Biociências, Universidade Estadual Paulista (UNESP), Botucatu, São Paulo, Brasil 3 Laboratório de Bioecologia e Sistemática de Crustáceos (LBSC), Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP), Universidade de São Paulo (USP), Ribeirão Preto, São Paulo, Brazil 4 Biology Department, American University, Washington, District of Columbia 5 Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia Correspondence Tavani Rocha Camargo, Aquaculture Center (CAUNESP), Universidade Estadual Paulista (UNESP), FCAV, Jaboticabal, São Paulo, Brasil. Email: rochatavani@gmail.com Funding information Conselho Nacional de Desenvolvimento Científico e Tecnológico, Grant/Award Number: FJZ PQ#303314/2017-7, FLM PQ#304968/2014-5 and PROTAX 440417/2015-5; Sao Paulo Research Foundation (FAPESP), Grant/Award Number: FJZ and FLM Biota#2010/50188-8, TRC#2012/14686-9 and TCR#2016/11182- 0; Coordenação de Aperfeiçoamento de Nível Superior—CAPES, Grant/Award Number: 1989/2014 - 23038.004309/2014- 51 and 2005/2014 - 23038.004308/2014-14 Abstract The families Aethridae and Calappidae were originally considered as part of the same family; however, their morphology and molecular biology separate them into two families. In this context, we describe the ultrastructure of spermatozoa of species of the Calappidae, Aethridae and Menippidae to elucidate the relationships among taxa. The vasa deferentia were submitted to routine protocols for transmission elec- tron microscopy. Our results indicate that the morphology of the spermatozoa of Hepatus pudibundus supports its exclusion from the Superfamily Calappoidea due to the presence of the apical striated layer. The spermatozoa of Menippe nodifrons is very similar to H. pudibundus and corroborates the recent phylogenetic analysis using sequence data of nuclear genes. Moreover, our results evidence two morpho- logical patterns of spermatozoa within Calappidae. Calappa ocellata and C. cinerea show spermatozoa with a wide acrosome vesicle, a thick operculum shaped as a shal- low “W” and a large thickened ring. Calappa gallus and C. hepatica show sperma- tozoa with a longer acrosome vesicle, a pointed operculum and a slender thickened ring. Our ultrastructure results conform with previous molecular proposal and show that spermatozoa ultrastructure can be an effective tool to adjust phylogenetic rela- tionship when used in association with molecular data. KEYWORDS Brachyura, crab, Decapoda, transmission electron microscopy