Final answer:
Fertilization triggers cortical rotation in amphibian eggs, which is important for establishing the embryo's body plan. This process involves the physical rotation of the egg's cytoplasm relative to the egg's cortex, redistributing maternal determinants.
Step-by-step explanation:
How does fertilization induce cortical rotation in amphibian eggs? In amphibian eggs, such as those of frogs and toads, fertilization starts a series of events that lead to the development of the embryo. A notable early event post-fertilization is cortical rotation, which is critical for establishing the future dorsal-ventral axis of the embryo. The process is initiated when a sperm penetrates the egg's outer layers, consisting of the corona radiata and the zona pellucida. Once the sperm reaches the oocyte's plasma membrane, the cortical reaction occurs. This entails the release of the egg's cortical granules, which triggers the rotation of the cytoplasm in respect to the egg's cortex. Cortical rotation is a physical rotation of the cytoplasmic layer external to the egg's central yolk. This action redistributes maternal determinants within the egg, setting up the initial body plan of the developing embryo.