Embryonic Development and Early Larval Survival Rate of the False Mussel Mytilopsis adamsi at Different Salinity Levels

The false mussel (Mytilopsis adamsi) is an economically important bivalve species with significant potential for aquaculture development in tropical regions. Understanding the optimal environmental conditions for embryonic development is crucial for successful hatchery operations and species management. This study investigated the effects of salinity on embryonic development duration and early larval survival rate of M. adamsi to determine optimal conditions for reproduction and early larval development. Fertilized eggs were exposed to four salinity treatments (10, 20, 30, and 40 ppt) and monitored for 21 hours. Embryonic development was tracked from unfertilized egg stage (UE) through early larval stage L-3, recording developmental progression and timing. Early larval survival rates were assessed at 21 hours post-fertilization. Water quality parameters including temperature, pH, dissolved oxygen, and ammonia were monitored throughout the experiment. Significant differences in survival rates were observed among salinity treatments (p < 0.05). All salinity treatments demonstrated complete developmental progression with 100% advancement to L-3 stage by 21 hours post-fertilization. Early larval survival rate followed a quadratic relationship with salinity (R² = 0.8251), with peak performance at 30 ppt (77.36 ± 2.82%) and 20 ppt (76.19 ± 4.17%). Low salinity (10 ppt) resulted in delayed development but maintained moderate survival rate (71.05 ± 6.39%), while high salinity (40 ppt) achieved rapid initial development but exhibited the lowest survival rate (54.63 ± 1.62%). The optimal salinity range for M. adamsi embryonic development and early larval survival is 20-30 ppt. This range provides the best balance between developmental efficiency and reproductive success, making it ideal for aquaculture applications. Despite achieving complete morphological development across all treatments, developmental completion does not guarantee physiological fitness, as evidenced by significant survival rate variations between salinity treatments. The findings have important implications for hatchery management and understanding the species' ecological distribution in estuarine environments.