Reproductive aspects of Siphonaria lessoni (Gastropoda: Heterobranchia) from the South-western Atlantic Ocean

KNACK DE ALMEIDA, H.; GIMÉNEZ, J.

Michigan

Congreso; American Malacological Society; 2015

Structuralcharacterization and reproductive cycle of Siphonaria lessoni wereinvestigated in Villa Gesell at Buenos Aires Province (37°16?S 56°58?W). S.lessoni is an herbivore gastropod commonly found inhabiting hard substratesin the intertidal zone of rocky shores along the South-western Atlantic Ocean.Artificial structures such as fishing docks introduced in sandy beaches likeVilla Gesell, provides a new substratum for this species settlement.Histological study of the gonad shows simultaneous hermaphroditism in thisspecies. The stage of gonadal development and oocytes size frequency in thefemale portion as the presence of sperm in the male portion were used toestimate reproductive events. The gametogenesis was observed synchronous forboth female and male portions. The oogenesis stages were defined by level ofoocytes development. Previtellogenesis oocytes as early vitellogenic were foundwithin gonad throughout the year. The mature oocytes, ripe of vitello, werealso found along the year but in high frequency during the beginning of theaustral summer. Spermatogenesis was continuous along the year. The spawningperiod in this species at the sampled site extended from November to February(end of austral spring and summer). This reproductive period was associatedwith changes in water and climate temperatures and photoperiod.