REVIEW Spermiogenesis and spermatozoal ultrastructure in Trichomycteridae (Teleostei: Ostariophysi: Siluriformes) Maria Ange ´lica Spadella, 1 Claudio Oliveira 2 and Irani Quagio-Grassiotto 2 1 Faculdade de Medicina de Marı ´lia, CP 2003, CEP 17.519-030, Marı ´lia, Sao Paulo, Brazil; 2 Departamento de Morfologia, Insti- tuto de Biocie ˆncias, Universidade Estadual Paulista, Campus de Botucatu, Distrito de Rubia ˜o Jr, s ⁄ n, CP 510, CEP 18.618-000, Botucatu, Sao Paulo, Brazil Keywords: catfish, cysts of spermatids, spermatozoa, morphology, phylogeny Accepted for publication: 8 June 2009 Abstract Spadella, M.A., Oliveira, C. and Quagio-Grassiotto, I. 2010. Spermiogenesis and spermatozoal ultrastructure in Trichomycteridae (Teleostei: Ostariophysi: Siluriformes). — Acta Zoologica (Stockholm) 91: 373–389. Siluriformes comprises the most diverse and widely distributed ostariophysan group, a fish assemblage that includes about three quarters of the freshwater fish of the world. In this study, the ultrastructural characterization of spermiogenesis and spermatozoa in specimens of Copionodontinae (the sister group to all other trichomycterids), Trichomycterinae (a derived trichomycterid group), and Itugl- anis (a genus not assigned to any trichomycterid subfamily) is presented. The comparative analyses of the data show that trichomycterid species share six of seven analyzed spermiogenesis characters, reinforcing the monophyly of the group. Analyses of trichomycterid sperm ultrastructure showed that the species studied share the same character states for nine of seventeen characters analyzed. Copionodon orthiocarinatus and Ituglanis amazonicus each share more ultrastruc- tural characters with species of Trichomycterus than with one another. Regarding the families of Loricarioidea, the species of Trichomycteridae share more charac- ters of spermatogenesis, spermiogenesis, and sperm with representatives of the families Callichthyidae, Loricariidae, and Scoloplacidae than with Nematogenyi- dae, its hypothesized sister group. With the exception of the family Nematoge- nyidae, the character similarities observed reinforce the monophyly of the superfamily Loricarioidea. Dra. Irani Quagio-Grassiotto, Departamento de Morfologia, Instituto de Bio- cie ˆncias, Universidade Estadual Paulista, Campus de Botucatu, Distrito de Rubia ˜o Jr, s ⁄ n, CP 510, CEP 18.618-000, Botucatu, SP, Brazil. E-mail: iraniqg@ibb.unesp.br Introduction Siluriformes comprises the most diverse and widely distrib- uted ostariophysan group, a fish assemblage that includes about three quarters of the freshwater fish of the world (Bur- gess 1989; Teugels 1996; Ferraris 1998, 2007; Nelson 2006). Among Neotropical lineages of Siluriformes that are likely to be monophyletic is the superfamily Loricarioidea (de Pinna 1998; Britto 2003) that comprises six families: Nematogeny- idae, Trichomycteridae, Callichthyidae, Scoloplacidae, Astroblepidae, and Loricariidae. According to two phylo- genies of the superfamily Loricarioidea, the family Tricho- mycteridae is sister to the Nematogenyidae (de Pinna 1998; Britto 2003). Trichomycteridae, one of the most speciose families of Loricarioidea, is considered to form a well-corroborated monophyletic group. Trichomycterids are divided into eight subfamilies: Copionodontinae, Trichogeninae, Trichomycter- inae, Vandelliinae, Stegophilinae, Tridentinae, Glanapterygi- nae, and Sarcoglanidinae (de Pinna and Wosiacki 2003). All of these subfamilies have been shown to be monophyletic, with the exception of Trichomycterinae (de Pinna 1998; de Pinna and Wosiacki 2003). In this study, the ultrastructural characterization of sper- miogenesis and spermatozoa in specimens of Copionodonti- nae (the sister group to all other trichomycterids), Trichomycterinae (a derived trichomycterid group), and Itugl- anis (a genus not assigned to any trichomycterid subfamily) is Acta Zoologica (Stockholm) 91: 373–389 (October 2010) doi: 10.1111/j.1463-6395.2009.00412.x Ó 2009 The Authors Acta Zoologica Ó 2009 The Royal Swedish Academy of Sciences 373