Zoological Studies

Reproductive Biology of the Freshwater Shrimp Atya scabra (Leach, 1815) (Crustacea: Atyidae) in Ilhéus, Bahia, Brazil

Alexandre Oliveira Almeida, Emerson Contreira Mossolin, and Joaldo Rocha Luz (2010) Reproduction and population aspects of the freshwater shrimp Atya scabra in the Santana River, city of Ilhéus, state of Bahia, Brazil, were studied from Apr. 2004 to May 2005.  During these 14 mo, 3752 individuals were captured, with a sex ratio of 1.01 males for each female.  The total number of individuals caught per month ranged 80-532.  Males were generally larger than females.  The smallest female found (5.40 mm in carapace length and 29.03 mm in total length) was ovigerous, which indicates that only adult individuals were caught.  Ovigerous females were found every month, which indicates continuous reproduction and a high index of reproductive activity during the year.  The highest reproduction indices were observed in May (94.3%) and Oct. (98.6%) 2004, and Mar. (93.7%) 2005.  Fecundity ranged 870-8907 eggs, with a mean of 3811 (±1992.87) eggs per female.  The size of the females and their fecundity were positively correlated.  The distribution of individuals in length classes by month showed that representatives of smaller classes occurred throughout almost the entire study period.  This indicates a constant input of individuals into the population, which corroborates the characterization of the reproductive period as being continuous, and explains the large numbers of ovigerous females found each month.  The 2nd abdominal segment is proportionally larger in females than in males, in width, height, and pleural length: these female secondary characteristics are related to an increased incubation area for eggs.