Direct Evidence for Mother-to-Embryo Transfer of Nutrients in the Livebearing Fish Gambusia geiseri
We present direct experimental evidence of maternal-to-embryo nutrient transfer in largespring gambusia, a species in which embryonic development was believed to depend solely on nutrients and energy sequestered in the egg prior to fertilization. Thirteen pregnant females were injected with tritiated leucine, and developing embryos of those individuals were assayed for radioactivity two hours postinjection. In eight females, one to all embryos in the developing brood showed significant uptake of labeled leucine. This finding suggests that matrotrophy may be an important maternal investment strategy for this species.Abstract
Dry mass (mean ± 1 SD) of Gambusia geiseri embryos of Stages 3 to 6 from collections at Head of the ver Ranch made in October 1983 and May 1987. Stages follow Meffe (1987). Figure redrawn from data presented in Dorsey (1990)
Radioactivity (disintegrations per minute) detected in individual embryos of seven Gambusia geiseri females from San Marcos Springs plotted as a function of wet mass per sample. Embryos of each female are enclosed by a polygon; labels refer to females identified in Table 1. One female (SM3) in which only one of nine embryos showed uptake of 3H-leucine is omitted from this graph (for clarity)
Relationship of radioactivity detected in embryos to that detected in the maternal liver. Percent of brood exhibiting uptake indicated by open circles. Mean activity of embryos in a brood indicated by solid circles. For mean activity detected in embryos, only those embryos that exhibited significant radioactivity were included