Reproductive biology of Alitta succinea (Annelida: Nereididae) in a Brazilian tropical lagoon

Alitta succinea is considered a cosmopolitan species in estuarine and coastal environments. It is also a model organism in marine chemical ecology and is used in ecotoxicological tests and molecular studies. We aimed to study the reproductive biology of the species in Lagoa de Maricá of Rio de Janeiro State, Brazil. For this purpose, monthly samples were taken from May 2015 to May 2016. The 653 individuals collected (sex ratio 1 male:1.5 female) were measured (width of the 20th chaetiger), sexed, and classified into stages by three criteria: the presence of gametes in the coelom; hypertrophy of the eyes; and modifications of the parapodia. From each identified female, the diameters of 30 randomly chosen oocytes were measured. Sediment samples were taken separately to analyze total organic matter and grain size. Salinity and temperature of the water were measured in situ each month. Our results show that individuals of this species reproduce through epitoky, with four stages of epitoky identified in both males and females. Parapodial modifications were more pronounced in males, in which some features such as the serrated papillae in the dorsal and ventral cirrus were exclusive.