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 tran sfer in largespring: gambusia, a species in which embryonic development was believed to depend solely on nutrients and energy sequestered in the egg p rior to fertilization. Thirteen pregnant females were injected with tritiat ed leucine, and developing embryos of those individuals were assayed for ra dioactivity two hours postinjection. In eight females, one to all embryos i n the developing brood showed significant uptake of labeled leucine. This f inding suggests that matrotrophy may be an important maternal investment st rategy for this species.