Size of first sexual maturity in Brachidontes rodriguezii (d?Orbigny, 1846) from south- western Atlantic Ocean

TORROGLOSA, M.E.; OJEDA, M.; KNACK DE ALEMIDA, H.; GIMÉNEZ, J.

Congreso; American Malacological Society; 2015

 The mussel Brachidontesrodriguezii (d´Orbigny, 1846)is the most abundant species of rocky shores intertidal at Buenos Aires cost. The intertidal communitycomplexity is related to the presence and developed of this mussel. Thetemporal and space variation of the community structure depend on physical(e.g. temperature, salinity and wave exposition) and biological factors (e.g.reproductive cycle and growth). Reproductive aspects as gametogenesis, spawningevents and size at maturity provide valuable information about the biology ofspecies and changes through time andspace. The objective of thisstudy was to estimate the size at first maturity of B. rodriguezii at artificial hard substrate. A histologicaldetermination was done during two consecutive reproductive events at summer2012 and 2013. Atotal of 335 specimens between 3 to 25 mm of total length were studied. Sexual maturity was related to gonadal activity. Twocategories of immature stages were described: undetermined (without gonadaldevelopment) and determined (with earlier gonadal development) where the gonadwas restricted to the dorsal region of the visceral mass. Meanwhile gonad ofmature males and females was completely developed in both lobes of the mantleand the visceral mass. At 4 mmshell length, oogenesis and spermatogenesis were observed. Minimum sizes atmaturity were 6.99 mmfor females and 6 mmfor males. The size of first maturity for the population, defined as the shelllength at which the 50% of the population reach the gonadal maturity was 8.30 mm for both sexes.