Carry-Over Effects of Broodstock Conditioning on the Salinity Tolerance of Embryos of the New Zealand Geoduck (Panopea zelandica)

Abstract

The New Zealand geoduck (Panopea zelandica) has seen considerable interest from the NZ aquaculture industry. A major bottleneck in culturing P. zelandica is early life stages mortality (e.g., embryo). Therefore, in this study, we investigated the embryonic performance and their transition to the first feeding larval stage (D-veliger) under different salinities (26, 30, 32, and 35 ppt) of four different offspring groups generated from broodstock being fed different ratios (25 : 75, 50 : 50, 60 : 40, and 75 : 25) of the haptophyte Tisochrysis lutea (formerly Isochrysis galbana) (ISO) and the diatom Chaetoceros muelleri (CM) during gametogenesis. Broodstock within all diet ratio treatments successfully conditioned, producing viable embryos. Average egg size ranged between 75 and 80 µm and was not affected by the diet ratios of the broodstock. Survival 48 hr postfertilization, D-veliger larvae yield, and incidence of abnormalities depended on both the embryo rearing salinity and broodstock feeding ratios. The combined salinity of 32−35 ppt and a feeding ratio of 50 : 50 and 60 : 40 (ISO:CM) had the highest survival of embryos (56.0%–77.5%), highest production of D-veliger larvae (>65%), and lowest incidence of abnormalities within D-Veliger (<47%). The size of the larvae decreased with decreasing salinities, with the largest found at 35 ppt (101.22 ± 0.49 µm in shell length). Embryos and larvae did not survive at salinity 26 ppt. These results suggest that diet during gametogenesis can play a role on the offspring ability to cope with environmental stressors at least during the critical first few days after fertilization. These findings provide important information on transgenerational effects due to broodstock diet, especially during the early life stages.