Abstract
The objective of this study was to evaluate the effects of water volume and water temperature on the sperm motility duration and the number of spermatozoa, and the water volume on the fertilization rates of oocytes of Rhinelepis aspera. Experiments were carried out to evaluate the effect of semen dilutions (1.74×10-5, 1.74×10-4, 1.74×10-3, 1.74×10-2, 1.74×10-1 and 1.00 mL of sperm.mL-1 of water) and water temperature (5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 oC) on spermatozoa motility duration. In addition, the effects of insemination dose (7×103, 7×104, 7×105, 7×106 and 7×107 spermatozoa.oocyte-1) and water volume (1.0, 30.0, 60.0, 90.0 and 120.0 mL water.2.0 mL-1 oocytes) on the artificial fertilization rates of oocytes were evaluated. The longest sperm motility duration were observed for the semen dilution of 1.74×10-5 mL semen.mL-1 water and in water at 5 oC. The highest fertilization rates were obtained for insemination doses between 7.00×103 and 1.23×107 spermatozoa. oocyte-1 and water volume of 28.11 mL water.2.0 mL-1 oocytes.
Highlights
Cascudo-preto (Rhinelepis aspera, Agassiz, 1829) is a species of fish that belongs to the family Loricariidae (Graça & Pavanelli, 2007)
The objective of this study was to evaluate the effects of water volume and water temperature on the sperm motility duration and the number of spermatozoa, and the water volume on the fertilization rates of oocytes of Rhinelepis aspera
The results show a tendency to plateau, with stable fertilization rate as a function of increasing spermatozoa:oocyte ratios between 7.0×103 and 1.23×107 spermatozoa.oocytes-1, resulting in a theoretical fertilization rate of 71.96% (Figure 1)
Summary
Cascudo-preto (Rhinelepis aspera, Agassiz, 1829) is a species of fish that belongs to the family Loricariidae (Graça & Pavanelli, 2007). In Brazil, it is found in the São Francisco and Paraná basins (Armbruster, 1998). The reproduction of this species is limited to lotic environments (Suzuki et al, 2000). It undergoes gonadal blockage and does not reproduce naturally in captivity and its reproduction must be induced with hormones (Zaniboni Filho & Weingartner, 2007). The knowledge about the artificial reproduction of this species may be relevant for the development of technological packages (López, 2005) for offspring production to meet the ornamental market demands (Hayashi et al, 2002; Guerreiro et al, 2011) and the storage or restocking programs (Carolsfeld et al, 2003). As a result of anthropogenic actions, R. aspera is a threatened species in some regions of Brazil (Mikich & Bérnils, 2004)
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