Sperm–Egg Interactions: Sperm–Egg Binding in Invertebrates


During fertilization, spermatozoa undergo a series of responses (including chemoattraction and the acrosome reaction) to egg‐derived factors before they contact the egg proper. Specific cell surface proteins direct the interactions between the sperm and the egg that lead to fusion and egg activation.

Keywords: fertilization; reproduction; egg; sperm; gamete

Figure 1.

Schematic drawing of a sea urchin sperm and egg. Note that they are not drawn to the same scale. (a) Sea urchin sperm. The head of sperm contains the acrosome and nucleus, the midpiece contains the mitochondria and centrioles, and the tail/flagellum contains the axoneme. Following the acrosome reaction, the acrosomal process extends from the tip of the sperm due to the polymerization of actin. (b) Sea urchin egg. During fertilization, the factors from the egg jelly are thought to activate and attract the sperm. Polysaccharides from the egg jelly induce the acrosome reaction in the sperm, which must then pass through the egg jelly and vitelline envelope to reach the egg plasma membrane. Following sperm binding/fusion with the egg, an increase of cytoplasmic free Ca2+ causes the cortical granules to fuse with the egg plasma membrane and the vitelline envelope lifts away from the egg and converts into the fertilization envelope.



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Further Reading

de Nadai C, Fenichel P, Donzeau M, Epel D and Ciapa B (1996) Characterisation and role of integrins during gametic interaction and egg activation. Zygote 4: 31–40.

Eisenbach M (1999) Sperm chemotaxis. Reviews of Reproduction 4: 56–66.

Foltz KR (1995) Sperm‐binding proteins. International Review of Cytology 163: 249–303.

Green JD and Summers RG (1982) Effects of protease inhibitors on sperm‐related events in sea urchin fertilization. Developmental Biology 93: 139–144.

Jaffe LA (1996) Egg membranes during fertilization. In: Schultz SG, Andreoli T, Brown A, Fambrough D, Hoffman J and Welsh M (eds) Molecular Biology of Membrane Transport Disorders, pp. 367–378. New York: Plenum.

Myles DG (1993) Molecular mechanisms of sperm‐egg membrane binding and fusion in mammals. Developmental Biology 158: 35–45.

Stricker SA (1999) Comparative biology of calcium signaling during fertilization and egg activation in animals. Developmental Biology 211: 157–176.

Wassarman PM (1999) Fertilization in animals. Developmental Genetics 25: 83–86.

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Carroll, David J(Mar 2003) Sperm–Egg Interactions: Sperm–Egg Binding in Invertebrates. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003298]