Polysperm refers to a phenomenon in reproductive biology where multiple sperm cells fertilize a single egg. The term is derived from the Greek words "poly," meaning many, and "sperm," meaning seed or sperm cell. Polyspermic fertilization can occur in various organisms, including mammals, fish, reptiles, and certain invertebrates.
In the context of human reproduction, polyspermic fertilization is an abnormal occurrence during the fertilization process. Ordinarily, upon sperm cell penetration, the outer layer of the egg, known as the zona pellucida, undergoes a chemical reaction that prevents additional sperm from entering the egg. However, in polyspermic fertilization, this mechanism fails, and multiple sperm cells successfully fuse with the egg, leading to an abnormal embryo.
Polyspermic fertilization often results in the development of aneuploidy, a chromosomal abnormality characterized by an abnormal number of chromosomes in the cells of the embryo. As a consequence, these embryos usually experience severe developmental defects and are generally not viable.
In certain assisted reproductive techniques, such as intracytoplasmic sperm injection (ICSI), polyspermic fertilization may occur intentionally or inadvertently. In these cases, the excess sperm that fertilize the egg are often manually removed to avoid abnormal embryo development.
Understanding polysperm and its effects on fertilization and embryonic development provides valuable insights into reproductive biology and can aid in the improvement of assisted reproductive technologies used in fertility treatments.
