Sturgeon Gut Development: A Unique Yolk Utilization Strategy Among Vertebrates Provisionally Accepted

Mujahid Shah¹ Xuan Xie² Marek Rodina¹ Jan Stundl^{1, 3} Ingo Braasch⁴ Radek Sindelka⁵ Małgorzata Rzepkowska⁶ Taiju Saito^{1, 7} Martin Psenicka^1*

• ¹South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Czechia
• ²Faculty of Fishery and Protection of Waters, University of South Bohemia, Czechia
• ³Division of Biology and Biological Engineering, California Institute of Technology, United States
• ⁴Ecology, Evolution, and Behavior Program, College of Natural Science, Michigan State University, United States
• ⁵Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology, Academy of Sciences of the Czech Republic, Czechia
• ⁶Department of Ichthyology and Biotechnology in Aquaculture, Institute of Animal Sciences, Warsaw University of Life Sciences, Poland
• ⁷South Ehime Fisheries Research Center, Ehime University, Japan

In vertebrates, maternally supplied yolk is typically utilized in one of two ways: either intracellularly by endoderm cells or extracellularly via the yolk sac. This study delves into the distinctive gut development of sturgeons, among the most ancient extant fish groups, contrasting it with other vertebrates. Our observations indicate that while sturgeon endodermal cells form the archenteron (i.e., the primitive gut) dorsally, the floor of the archenteron is uniquely composed of extraembryonic yolk cells (YCs). As development progresses, during neurulation, the archenteric cavity inflates, expands laterally, and roofs a semicircle of YCs. By the pharyngula stage, the cavity fully encompasses the YC mass, which begins to be digested at the hatching stage. This suggests a notable deviation in sturgeon gut development from other vertebrates, as their digestive tract initiates its function by processing endogenous nutrition even before external feeding begins. Our findings highlight the evolutionary diversity of gut development strategies among vertebrates and provide new insights into the developmental biology of sturgeons.