Embryonic nutrition, growth and energetics in Zoarces viviparus L. as indication of a maternal-fetal trophic relationship.

The embryos of Zoarces viviparus (L.) show linear growth during their intraovarian development. In early gestation before hatching, the embryos take up very small amounts of low molecular tracer compounds such as glucose, glycine or taurine. Later in gestation (two months after hatching), the embryos accumulate substantial amounts of the tracer compounds. The uptake rates of the tracer compounds in vitro are correlated with ambient concentrations of unlabelled compounds within the natural concentration range of the ovarian fluid. The highest uptake rates are found for glucose and the lowest for taurine. Release of 14CO2 and dissolved organic carbon (DO14C) from assimilated tracers in the embryos is low. Oxygen uptake and body weight of the embryos appear to be linearly correlated, and the average oxygen uptake is 4.20 (SD 0.73) mumol O2 g-1 h-1 WW at 11 degrees C. The contribution of glucose respiration to total aerobic respiration is 13.9%. A growth to respiration ratio of 0.91 indicates a relatively high efficiency for converting food to growth.