Reproductive traits of the freshwater prawn Macrobrachium amazonicum (Decapoda: Palaemonidae) in an isolated water reservoir

The aim of this study was to analyze the reproductive period, fecundity, egg size and reproductive output (RO) of a hololimnetic population of Macrobrachium amazonicum. The prawns were collected monthly, from May 2017 to April 2018, in a water reservoir isolated from river connections, in Severinia (20o49’31.92” S, 48o49’39.55” W), Sao Paulo, Brazil. Ovigerous females were preserved individually in 70% ethanol. The reproductive period was calculated based on the monthly percentage of ovigerous females. The egg mass was weighed and partially measured. The eggs were counted and classified according to the embryonic developmental stage. The reproductive output was calculated individually by dividing the dry weight of females without eggs by the mass of eggs. The reproductive period was continuous, with peaks in the dry season. Egg volume differed among stages and seasons (ANCOVA, p < 0.05), being larger in the rainy season. The reproductive output differed between seasons (rainy: 12.5 ± 4.8%; dry: 13.9 ± 5.4%, p < 0.05), as well as fecundity (rainy: 585 ± 304 eggs; dry: 613 ± 306 eggs, p < 0.05). We concluded that the reproductive traits of this population differ from those of other populations of M. amazonicum previously studied, and that these differences may be consequences of the isolation of this population.