Early developmental stages of Amazonian pacu <i>Prosomyleus rhomboidalis</i> derived from <i>in loco</i> reproduction

ABSTRACT The objective of this study was to characterize macroscopically the female gametes, evaluate the survival rates, as well as describe in detail the embryonic development of Prosomyleus rhomboidalis . Three adult females from the Xingu River, presenting promptly ovulation were fertilized by the dry method using sperm from adult males. Egg incubation was set at 27.5°C, and oocyte characteristics and the main developmental stages were described. The results showed that the non-hydrated oocyte has an average diameter of 2.12 mm, yellow colour, spherical shape, is non-adhesive and the diameter increased after hydration at 0.36 mm, referring to the perivitelline space(PS). The fertilization rates (96.79 ± 9.52%) and hatching of normal larvae (96.21 ± 2.40%) were analysed, with hatching above 96%. After hydration of the eggs the PS arose and formed a visible animal pole ending with the hatching of the larvae 69 h and 39 min after fertilization. The description of developmental stages following fertilization was described for the first time in this species. The information presented in this work will serve as a basic support for new possibilities in conservation strategies, re-stocking and genebanking.