Vitelline membrane

Definition

The acellular protein envelope surrounding the plasma membrane (oolemma) of an oocyte or egg, lying between the oolemma and any external coatings such as the chorion. In insects and other arthropods, it forms during oogenesis as a secretion of the follicular epithelium, becomes the innermost layer of the mature egg's egg envelope, and persists through early embryogenesis until hatching. It contains species-specific sperm-binding receptors that mediate fertilization specificity and serves as a selective barrier between the yolk and the developing embryo.

Etymology

From Latin vitellus (yolk) + -ine (of or relating to) + membrane, referring to its position adjacent to the yolk mass.

Example

In Drosophila melanogaster, the vitelline membrane assembles from three major proteins (VMPs) secreted by follicle cells; after fertilization, it remains intact while the cellular blastoderm forms beneath it, and is finally shed at larval hatching.

Synonyms

• vitelline envelope
• zona pellucida (mammalian equivalent)

Related Terms

• Chorion
• oolemma
• perivitelline space
• follicular epithelium
• Vitellogenesis
• fertilization envelope
• Serosa

Usage Notes

In entomology, distinguished from the chorion (the outer, often sculptured eggshell) and the oolemma (the egg's own plasma membrane). The term 'zona pellucida' is reserved for mammals; 'vitelline membrane' is standard for arthropods and most non-mammalian animals. Some authors use 'vitelline envelope' interchangeably, though 'membrane' predominates in insect literature.