Seasonal variation in population structure and sexual maturity of Sylviocarcinus pictus (Decapoda: Trichodactylidae) in a Neotropical intermittent river

Sylviocarcinus pictus is a South American freshwater crab recently recorded for the first time in the Caatinga biome. Our objective was to characterize the population and reproductive biology of S. pictus from the semi-arid northeastern region of Brazil and verify the influence of seasonal environmental changes in this population. The crabs were collected from a stretch of Guaribas River, PI, Brazil, every month between October 2013 and September 2014. The crabs were identified, sexed and the carapace width (CW) was measured. Physiological sexual maturity was determined based on the gonadal development stage. A total of 178 crabs were obtained (111 males and 67 females), with a sex ratio biased towards males 1.66:1. The number of crabs collected was higher in the months of drought. Males and females reach physiological sexual maturity with 36.80 and 34.20 mm of CW, respectively. The occurrence of individuals with developed or developing gonads throughout the study indicates that these crabs reproduce continuously during the year, although recruitment was higher in February and May. Our results indicate that this population uses a reproductive strategy to optimize its reproductive fitness in an intermittent environment.