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Embryology of sea urchin: blastula stage
Legend:
1 blastocoel (transparent, central)
English name: Sea urchin
Scientific name: Psammechinus sp.
Familia: Echinidae
Classis: Echinoidea
Phylum: Echinodermata
Regnum: Animalia
After the morula stage the blastomeres arrange so a mono-cellular coat around a central vacity (the blastocoel) is formed. This stage is called the blastula stage (blastula = vesicle-like). The embryo secretes a hatching enzyme that causes proteolytic degradation of the fertilization membrane. The epithelium of the cells at the vegetal pole thickens. The vegetal plate arises.
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