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

1077-8306

Histological characterization of the hermaphroditic gonad (HG) and seasonalityof gametogenesis were investigated in a population of Siphonaria lessonii from the coast ofBuenos Aires Province (37°160S, 56°580W). Monthly analysis of the frequency of gametogenicstages, as well as the number and mean size of oocytes, were used to determine reproductiveevents over a 2-year period (June 2012–May 2014). Female and male gametes wereobserved simultaneously within acini of adult individuals and continuously throughout theperiod studied. Oogenesis commenced in the beginning of austral autumn, with gonadscharacterized mainly by proliferation of female cells. From this moment, oocytes graduallyincreased in number and area until spring, when a large number of individuals were foundin the evacuation stage. The same trend was observed from early gonad maturation toadvanced stages, indicating that gonad development was closely related to the frequency ofoocyte stages and to the area (size) of oocytes. Spermatogenesis was also observed as a continuousprocess throughout the year, although spent acini were more frequent from Novemberuntil February. Reproductive seasonality and gametogenesis were associated withchanges in temperature and day length.