Sturgeons, one of the oldest living fish species, differ from other vertebrates with their unique gut development. While in most vertebrates the yolk of the egg serves as a source of nutrition either intracellularly (within endoderm cells) or extracellularly via the yolk sac, sturgeons have evolved a different strategy.
During embryonic development, specialized yolk cells form in the vegetal hemisphere of the embryo. These cells serve exclusively to provide endogenous nutrition to the developing embryo. As the sturgeon’s gut develops, it gradually surrounds these yolk cells and begins digesting them before the embryo consumes any external food. This remarkable ability to digest its own endogenous nutritional source within the gut during embryonic development represents a unique adaptation among vertebrates.
Primordial germ cells (PGCs), the precursors of reproductive cells, also arise from these yolk cells. What sets them apart from other yolk cells is the presence of germ plasm, which specifies their future role. After their formation in the vegetal pole of the egg, PGCs must migrate away from the digestion zone to the germinal ridge, where they contribute to the development of the reproductive system. This combination of early digestion of endogenous nutrition and the migration of specified germ cells highlights the evolutionary distinctiveness of sturgeon development compared to other vertebrates.
This discovery underscores the sturgeon’s unique adaptations, allowing them to optimize both nutrition and the development of reproductive cells during embryogenesis. It also demonstrates how different evolutionary strategies contribute to the survival of ancient fish species. Sturgeons not only reaffirm their exceptional place among fish but also provide new insights into the diversity of developmental processes in vertebrates.
Detailed information can be found in the original article: Shah, M.A., Xie, X., Rodina, M., Štundl, J., Braasch, I., Šindelka, R., Rzepkowska, M., Saito, T., Pšenička, M., 2024. Sturgeon gut development: a unique yolk utilization strategy among vertebrates. Frontiers in Cell and Developmental Biology 12: 1358702. https://doi.org/10.3389/fcell.2024.1358702
Written by: Martin Pšenička, PhD.
Fig. 1: Larva of Sterlet Sturgeon: Excretion of Digested Yolk Before First Feeding
Fig. 2: Comparison of Gut Development in Fish. The yolk is shown in yellow and the digestive tube in green.
