Gonad characterization and reproductive seasonality in Siphonaria lessonii (Gastropoda: Heterobranchia) from the Southwestern Atlantic Ocean

HENRIQUE KNACK DE ALMEIDA; GIMENEZ, JULIANA

INVERTEBRATE BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018 vol. 137 p. 264 - 277

1077-8306

Histological characterization of the hermaphrodite gonad and gametogenesisseasonality were investigated in a population of Siphonaria lessoniifrom the coast of Buenos Aires Province (37°16?S 56°58?W). Monthly analysis ofthe frequency of gametogenic stages as well as the number and mean size of oocyteswereused to determine reproductive events over a 2-year period (June 2012 - May2014). Female and male gametes were observed simultaneously within acini ofadult individuals and continuously throughout the period studied. Oogenesiscommenced in the beginning of austral autumn with gonads characterized mainly byproliferation of female cells. From this moment oocytes gradually increased innumber and area until spring when a large number of individuals were found inevacuation. The same trend was observed from early gonad maturation to advancedstages indicating that gonad development presented a close relation withoocytes frequency and area. Spermatogenesis was also observed as a continuousprocess throughout the year, although spent acini were more frequent fromNovember until February. Reproductive seasonality and gametogenesis wereassociated with changes in temperature and duration of the daylight period.