Determinação da concentração espermática para melhor taxa de fertilização do híbrido tambacu (Colossoma macropomum X Piaractus mesopotamicus)

Abstract

The techniques of artificial reproduction by inducing reproductive fish that inhabit running waters(reofílicos) is part of everyday life in the fish farms in Goiás.These techniques must be refine in order to provide a better fertilization rate of sperm/oocyte.The hybrid tambacu is one of the most grown fish in Brazil, from the cross of tambaqui´s female(Colossoma macropomum) and pacu´s male(Piaractus mesopotamicus), because it stands better low temperatures, and it shows faster growth than pacu and tambaqui. In order to determine a better sperm concentration of tambacu´s cross-bred fertilization (Colossoma macropomum x Piaractus mesopotamicus), it was selected tambaqui´s female with advanced gonadal maturation, domed abdomen and redish genital papilla and a pacu´s male with semen output by light abdominal massage in the anterior-posterior sense. The female and the male were prompted to reproduction with pituitary extract: female (1º dose 0,5 mg/kg and 2º dose 5mg/kg), male (songle dose 3mg/kg) The female released 654g of oocytes with 1560 oocytes/g, with a reason of 170.040 oocytes/kg, the oocytes were distributed in 5 treatments with three repetition: T1=1g, T2=1,5g, T3=2g, T4=2,5g e T5=3g. The male produced 2ml of semen with 10x109sperm/ml with more than 90% of motility. For fertilization were applied 2 Xl of fresh semen in each repetition (T1=128.205, T2=85.470, T3=64.102, T4=51.282, T5=42.735 sperm /oocyte). After 11 hours of incubation were analyzed the fertilization rates for each treatment. Te best connection sperm/oocyte was found in T4=51.282 sperm/oocyte. For a better fertilization rate of the hybrid tambacu it is recommended 1ml of pacu´s semen for each 125g of tambaqui´s oocyte.