The Fate of the Kolk Syncytial Layer during Postembryonic Development of Stenodus leucichthys nelma

The yolk syncytial layer (YSL) is a multifunctional transient structure of teleost embryos and larvae. The YSL performs nutritional, morphogenetic and immune functions. However, the data on the YSL structure in different teleost species is fragmented. We aimed to characterize YSL of the postembryonic inconnu (Stenodus leucichthys nelma) along with the depletion of maternal reserves by analyzing serial histological sections. At hatching, the yolk complex was located anterior to the liver and contained a large oil globule (OG) in the front region, 1–2 additional OG, and the yolk itself. The YSL region around the OG was striated, the region surrounding the yolk was regionalized in an apico-basal direction. The yolk syncytial nuclei (YSN) were large and complex-shaped. The yolk was exhausted by approximately the 17th day post hatching (dph). One–two large OG remained in the yolk complex until the programmed death of the YSL at 31 dph. The organization of the larval yolk complex of the inconnu was typical for Coregonidae. The abundance of comet-shaped YSN was its peculiarity.