No abstract

Summary Knowledge of the sperm–oocyte ratio in fish fertilization serves as the basis for studies on artificial reproduction and gamete manipulation. The aim of this study was to determine the minimum insemination dose for Brycon amazonicus oocyte fertilization. Female and male gametes were used and tested with the following doses of spermatozoa oocyte–1 ml–1: 10,000, 20,000, 40,000, 60,000 and 80,000 (in triplicate). Fertilization rates were calculated and estimated from the regression equation by applying the segmented regression model ‘Linear Response Plateau’ to determine the appropriate proportion of gametes. Based on the equation Ŷ = 14.3415 + 0.0007836X, the fertilization rate increased up to 63.34% as it reached a plateau with a proportion of 62,524 spermatozoa oocyte–1 ml–1, which is the minimum insemination dose recommended for artificial insemination of the species.

SummaryThe aim of this study was to evaluate if hormonal treatment causes changes in the morphology of matrinxã Brycon amazonicus spermatozoa. Twelve males were randomized into three treatment groups: 1, Ovaprim™ (0.5 ml/kg); 2, carp pituitary extract (CPE; 2.0 mg/kg); and 3, NaCl solution 0.9% - control group (0.5 ml/kg); with four replicates. Morphological sperm analysis was performed using an optical and scanning electron microscope. The percentage of normal spermatozoa (49.6±4.6% to 60.8±2.8%), with primary (26.1±6.4% to 45.3±4.5%) and secondary abnormalities (4.4±2.9% to 13.9±3.5%) did not differ significantly between treatment groups. There were no significant differences between treatments in relation to the primary abnormalities found in the head (10.5±3.8% to 25.5±6.3%), the midpiece (0.1±0.1% to 0.2±0.2%) and in the flagellum (18.9±3.8% to 15.5±3.1%), as well as in the secondary abnormalities, located in the head (0.8±0.4% to 7.8±4.6%) and in the flagellum (2.2±1.1% to 6.1±1.5%). When each abnormality was evaluated individually, only the percentage of degenerated head was higher in the CPE-induced group (24.9±5.9%) than the control group (7.2±3.1%). We concluded that the use of pituitary extract of carp or Ovaprim™ under the conditions of this experiment does not influence the percentage of sperm abnormalities in B. amazonicus.