Spermatogenic evaluation, cryogenic preservation and fertility of the "pacu" Piaractus mesopotamicus [Holmberg, 1887], sperm, from induced spawning

Abstract

In order to develop the artificial reproduction in freshwater fishes that can be considered as commercial stocks to be explored in aquaculture, the seminal characteristics, cryogenic preservation and fertility of "pacu", Piaractus mesopotamicus, sperm are studied. The males from induced spawning were kept in experimental ponds at the Biology Laboratory of Freshwater Fishes "Dr. Pedro de Azevedo" - IP/SAA- and Research and Training Aquaculture Center - CEPTA/IBAMA - in Pirassununga (São Paulo - Brazil). The assay was performed during January from 1985 to 1990. The seminal characteristics examined and values obtained were: sperm volume, 5.02 ml; percentage of motile spermatozoa, 90.00%, spermatic concentration, 28.07 x 10⁶/mm³; percentage of live spermatozoa by differential staining method, 89.10%. The condition coefficient between spermatic concentration (mm³) and spermatocrit (mm) was found to be r=0.93* and the average of the methylen-blue reduction test was 150 seconds. The sperm was frozen in liquid nitrogen vapor and the cryogenic preservation was carried out in a special container. After twenty-four hours of freezing, the sperm was thawed and under microscopy examination showed 20% live spermatozoa. After one year of cryopreservation, the fertilization test revealed 21.07% of fertilized eggs, whereas for the control fresh sperm the fertility was 34.55%. Therefore, it is feasible the sperm cryopreservation of the "pacu" and its utilization in the artificial reproduction routine.