Please cite this article in press as: Vergilio, C.S., et al., Evolution of cadmium effects in the testis and sperm of the tropical fish Gymnotus carapo. Tissue Cell (2015), http://dx.doi.org/10.1016/j.tice.2015.02.001 ARTICLE IN PRESS G Model YTICE-927; No. of Pages 8 Tissue and Cell xxx (2015) xxx–xxx Contents lists available at ScienceDirect Tissue and Cell j o ur nal ho mepage: www.elsevier.com/locate/tice Evolution of cadmium effects in the testis and sperm of the tropical fish Gymnotus carapo C.S. Vergilio a , R.V. Moreira a , C.E.V. Carvalho b , E.J.T. Melo a,∗ a Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes 28013-602, RJ, Brazil b Laboratório de Ciências Ambientais, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes 28013-602, RJ, Brazil a r t i c l e i n f o Article history: Received 6 December 2014 Received in revised form 3 February 2015 Accepted 3 February 2015 Available online xxx Keywords: Cd effects Metal Morphology Spermatozoa Testis Tropical fish a b s t r a c t The present study investigated the testis and sperm morphology of the tropical fish Gymnotus carapo after exposure to increasing CdCl 2 concentrations (5–40 M) for 24 and 96 h. The treatments induced Cd accumulation in the testis and a decrease in the gonadosomatic index from a 10 M. Cd induced alterations in testis since 24 h; however the extension and severity of damages increased after 96 h in all tested concentrations. Marked variations in the cysts size, proliferation of the interstitial tissue, infiltration of inflammatory cells, necrosis, reduction of germ cells and sperm aggregation was observed in 96 h treated fishes. In this time, there was a complete absence of germ cells in the testis of fish treated with 40 M. The ultrastructural analysis allowed for the visualization of the initial damages over germ cells, such as the presence of vacuoles in the cytoplasm of spermatogonia, spermatocytes, and spermatids. Exposed fish (20 M for 24 and 96 h) had alterations in sperm number and morphology. These results are important for establishing a direct correlation between the Cd accumulation and incidence of damages and can help characterize the mechanism of Cd-induced pathogenesis in the male reproductive system. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The testis morphology consists of germ cells in different stages of differentiation that undergo several processes of division until there is release of mature spermatozoa. The integrity of such cells is essential for developing future generations, affecting the survival of offspring (Friedmann et al., 1996). This arrangement and the fre- quency of cell division makes this organ highly vulnerable to some pollutants (Bonde, 2010). Morphological investigation in the testis is a relevant aspect of toxicological evaluations because adverse effects in this organ can directly influence several reproductive processes, such as spermatogenesis which may directly affect the fertilization success (Crump and Trudeau, 2009) and the develop- ment of the embryonic and postembryonic stages (Sellin and Kolok, 2006). Cadmium (Cd) is a toxic metal that can induce adverse effects in the male reproductive system of several animal species, including ∗ Corresponding author at: Universidade Estadual do Norte Fluminense, Centro de Biociências e Biotecnologia, Laboratório de Biologia Celular e Tecidual, Av. Alberto Lamego, 2000, Parque Califórnia, CEP 28013-602 Campos dos Goytacazes, RJ, Brazil. Tel.: +55 22 2739 7175. E-mail addresses: ejtm1202@gmail.com, ejtm@uenf.br (E.J.T. Melo). humans (Thompson and Bannigan, 2008). Fish are good models for evaluating the toxic effects of Cd because the aquatic systems are the final receptacle of chemical substances. Further, the consump- tion of contaminated fish and seafood is one of the main sources of Cd exposure in human populations. Therefore, the study of Cd accumulation and effects in fish can express both the human and ecological health (Ju et al., 2012). Recent studies have shown the effects of dietary Cd exposure in the testis of red tilapia with degeneration of spermatogenic elements, fibrosis of lobule walls and blood infiltration (El-Refaiy and Eissa, 2013). Disorganization of testicular lobules was also observed in Puntius sarana (Kumari and Dutt, 1991) and Salveli- nus fontinalis (Sangalang and O’Halloran, 1972) after Cd exposure through injection or waterborne administration, respectively. Cd waterborne exposure also induced testicular apoptosis in Labeo bata (Das, 1988) and Gobius niger (Migliarini et al., 2005). Despite these known effects, the steps involved in the development of Cd- induced pathogenesis in the male reproductive system of fish is not fully described, and the evaluation of the progression of Cd effects in the testis remains unclear. Further, the cellular processes involved in the death of germ cells after Cd exposure has not been fully investigated. A decrease in the sperm motility, speed and trajectory have also been demonstrated following Cd exposure in different fish http://dx.doi.org/10.1016/j.tice.2015.02.001 0040-8166/© 2015 Elsevier Ltd. All rights reserved.