Extension of sperm motility leads to increased rates of fertilization and hatching in curimba, Prochilodus lineatus By E. E. Hern andez Cuadrado 1,2 , L. D. Solis Murgas 2 , V. de Oliveira Felizardo 2 , M. Rodrigues Ferreira 2 and E. de Souza Andrade 2 1 Faculty of Veterinary Medicine and Animal Science, University of Tolima, Altos de Santa Helena, Ibague´, Colombia; 2 Postgraduate Program in Veterinary Sciences, Laboratory of Physiology and Pharmacology, Federal University of Lavras, Lavras, Minas Gerais, Brazil Summary The objective of this study was to evaluate the effects of six activating solutions on duration of sperm motility, fertiliza- tion rate (FR), and hatching rate (HR) of Prochilodus linea- tus (Valenciennes, 1837). The activating solutions (SA) used were: SA 0 (199 mOsm kg 1 , pH 8.5), SA 1 (138 mOsm kg 1 , pH 7.5), SA 2 (256 mOsm kg 1 , pH 7.5), SA 3 (131 mOsm kg 1 , pH 10), NaCl (92 mOsm kg 1 , pH 7.5) and distilled water (32 mOsm kg 1 , pH 7.5). SA 1 induced the highest motility, FR and HR, compared with the other activating solutions. The lowest motility was obtained with SA 0 , with no fertilization or hatching, whereas motility was zero with SA 2 and SA 3 . It is possible to conclude that the solution SA 1 can be used for the activation of gametes dur- ing fertilization in induced reproduction of curimba to achieve higher fertilization and hatching rates. Thus, it was found that the osmolality and pH of activating solutions, probably with the participation of dissolved substances therein, are the main factors acting on semen motility after activation. Introduction The curimba Prochilodus lineatus (Valenciennes, 1837) is a migratory species widely distributed in South America, and highly valued in commercial and subsistence fishing. Of great economic and ecological importance among native medium and large sized fish species in Brazil, the curimba reproduces between the months of October and March (Botta et al., 2010). The population stocks of this species have been greatly affected by commercial activities, including overfish- ing, habitat alteration, variations in water quality (Carolsfeld and Harvey, 1998), dam construction, and illegal fishing (Pesoa and Schulz, 2010). Studies focusing on optimizing their reproduction are thus needed in order to prevent extinc- tion and to ensure permanence of the species as a food source. Among these efforts are noteworthy male reproduc- tive biology studies that evaluate semen quality and sperm fertilizing capacity (Valdebenito et al., 2009). The sperm of most freshwater fishes such as curimba remain stationary within the testes, seminal plasma, and in isosmotic (freshwater fish) media, whether or not they are electrolytic solutions (Bastami et al., 2010). In addition, the duration of sperm motility after sperm activation in these fishes is typically short, and wholly dependent on the solu- tion used in the activation procedure (Ingermann et al., 2011). Characteristics such as ion concentration, osmolality, and pH of the medium activator can also change the dura- tion of the sperm motility (Alavi and Cosson, 2006; Cosson, 2010). The brevity of this period of sperm motility has been reported using traditional sperm activators, such as hypo- tonic solutions of sodium bicarbonate, NaCl, and KCl, at different concentrations. In turn, the fertilizing capacity of the fish sperm determines its quality, which can be evaluated by sperm motility (Rurangwa et al., 2004). However, these and other sperm characteristics of some fish species are only poorly characterized (Alavi and Cosson, 2005, 2006), and not all factors involved in activation are well understood. In the case of curimba semen, the average duration of sperm motility is two minutes, at a pH of 7.8  0.4, with no motil- ity in media with 277 mOsm kg 1 of osmolality (Orf~ ao et al., 2010; Miliorini et al., 2011). The short duration of motility in curimba sperm complicates studies of the physiol- ogy of the activated sperm, and can be a limiting factor in artificial fertilization of oocytes, especially in instances of low semen production. In general, through the use of artificial sperm activators, average motility times in teleosts ranging from 30 s to 3 min have been achieved. However, activation of sperm up to between 10 and 15 min in Cyprinus carpio and Danio rerio using a solution of this type has recently been reported (Jing et al., 2009; Bastami et al., 2010). The prolongation of sperm motility has great importance for fish culture because it offers an alternative for the pro- duction of viable embryos and larvae. This could facilitate fertilization at various times after sperm activation, which could increase the number of fertilized oocytes using a smal- ler amount of semen. It would also be possible to increase productivity, since the economic success of artificial insemi- nation production projects in fish are dependent on maximiz- ing the benefits in use of the gametes (Billard et al., 1996). Keywords: Native Fish, Sperm Activation, Osmolality, Embryos, Larvae U.S. Copyright Clearance Centre Code Statement: 0175-8659/2014/3002–329$15.00/0 J. Appl. Ichthyol. 30 (2014), 329–333 © 2013 Blackwell Verlag GmbH ISSN 0175–8659 Received: November 16, 2012 Accepted: March 30, 2013 doi: 10.1111/jai.12259 Applied Ichthyology Journal of