Dottervorrat

Dottervorrat is a term used in zoology and embryology to denote the yolk reserves stored in the ovum of egg-laying animals. It serves as the primary source of nutrients and energy for the developing embryo before and during early development. The size, composition and distribution of the Dottervorrat vary between species and egg types.

Most of the Dottervorrat is lipids and proteins, organized as granules or droplets such as lipovitellin and phosvitin, with smaller amounts of carbohydrates and minerals. Yolk is produced in the mother's body (for birds, in the liver) and transported to the ovary and oviduct, where vitellogenesis deposits yolk precursor material into the oocyte. The yolk composition reflects maternal diet and physiology and affects egg quality and embryo viability.

During development, the yolk provides energy and raw materials. In birds and other meroblastic eggs, the yolk remains concentrated in the vegetal pole and is gradually consumed as the embryo grows; in some fish and amphibians, yolk distribution and usage follow different patterns but the yolk remains the main nutrient source until hatch or the onset of external feeding.

The Dottervorrat is influenced by ecological and life-history factors, such as egg size, clutch number, and parental care, and it evolves in concert with reproductive strategies. The term emphasizes maternal provisioning of resources that support embryogenesis.

Etymology: Dotter means yolk and Vorrat means reserve in German; the term is used in German-language literature on embryo development.