🥚
Reproduction
Fish Embryology & Development
The developmental biology of fish - from fertilised egg through free-swimming fry, one of the fastest and most externally observable life-cycles in vertebrates.
System: Reproductive Level: Advanced Discipline: Cellular
📖 Overview
Fish embryology is transparent - literally. Zebrafish embryos are so translucent researchers can watch every cell divide in real time. This is why zebrafish became the vertebrate development model, illuminating heart formation, spinal cord development, and even human birth defects. The developmental sequence itself - cleavage, gastrulation, neurulation, organogenesis, hatching - is conserved across most vertebrates and traces back to a common ancestor.
⚙️ Mechanism
Yolk-rich egg. Cleavage divisions atop the yolk (meroblastic in most fish). Blastula → gastrula → neurula → embryo. Hatching triggers by proteolytic enzymes softening egg membrane. Larval yolk-sac stage. Free-swimming fry.
🔑 Key Concepts
Meroblastic cleavage, gastrulation, neurulation, somitogenesis, hatching enzyme, yolk-sac stage.
🎯 Applications
Zebrafish as biomedical model - drug screening, neurodegeneration, organogenesis research. Aquaculture larviculture depends on understanding developmental windows.
✨ Fun Fact
You can watch a zebrafish heart start beating - live, under a microscope - about 22 hours after fertilisation. The embryo is transparent enough to see individual cells at every stage.