Controlled reproduction of penaeid shrimp: a contribution to its improvement

This dissertation deals with controlled reproduction of penaeid shrimp. New knowledge about natural reproductive activity of Penaeus occidentalis in Gulf of Nicoya, Costa Rica, is presented. Since in vitro fertilization of open thelycum shrimp proved unsuccessful, a hypothesis is given to explain experimental results. In P. setiferus , the Male Reproductive Blackening Disease was studied, and bacterial infection was found to be associated with the male's condition. Production of spermatophores in captivity was explored in two species, P. stylirostris and P. vannamei . Adequate husbandry as well as successive ejaculation improved spermatophore quality. Deterioration of spermatophores was observed as part of a normal process for renewal in P. vannamei , without pathological implications. In order to further improve spermatophore quality, the injection of 17-alpha-methyltestosterone and 17-alpha-hydroxyprogesterone at 0.01 and 0.1 µg g ^-1 body weight was evaluated. 17-alpha-methyltestosterone significantly improved the quality of spermatophores, whereas 17-alpha-hydroxyprogesterone did not. Serotonin injection was evaluated as an alternative to female's eyestalk ablation for induction of ovarian maturation and spawning in P. vannamei . This neurotransmitter induced lower maturation and spawning with 3 doses of 50 µg g ^-1 body weight, than eyestalk ablation. In other to lay a basis for cryopreservation, penaeid embryos were evaluated in terms of their tolerance to cooling, cryoprotectants, and hypersaline solutions. T. byrdi morulae and advanced embryos (10 h) were tolerant to cooling at 10 °C, but were very sensitive to 0 °C. Embryos showed high tolerance to methanol and intermediate tolerance to dimethyl sulfoxide. Morulae were more resistant to hypersaline treatment at 55 ppt than advanced embryos.