Effects of salinity on pre- and post-fertilization developmental events in the clam (Linnaeus, 1767).

The knowledge about the effect of salinity on the physiological mechanism of bivalve reproduction is fundamental to improve production strategies in hatcheries. The present work evaluated the influence of different salinity concentrations (15, 20, 25, 30, 35 and 40 g⋅L) on pre- and post-fertilization development processes in the clam, , oocytes obtained by stripping. Salinity directly interfered with the germinal vesicle breakdown (GVBD) rate and in the cellular stability of unfertilized oocytes. Salinity concentrations between 30 and 35 g⋅L provided better percentages of stable GVBD within 120 min, and incubation of oocytes in the salinity range of 30-35 g⋅L for a time interval of 80-120 min provided > 80% GVBD. In the post-fertilization analysis, salinity affected the rate of the extrusion of the first and second polar bodies (PB1 and PB2). The release of 50% of the PBs was faster at a salinity of 35 g⋅L, with an estimated time of 10 min for PB1 and 30 min for PB2. Thus, chromosome manipulation methodologies aiming triploids should be applied at 35 g⋅L salinity, with application of post-fertilization shock before 10 min for PB1 retention or before 30 min for PB2 retention.