Asexual reproduction is a method of reproduction in which the organism is basically making clones of itself. This method of reproduction differs from sexual reproduction as it does not require gametes (sperm and egg) from the opposite sexes. In bacteria, fungi and plants, asexual reproduction is very common and is usually used along with sexual reproduction as a method to further greatly the chances of the organism’s genes being passed along. Asexual reproduction in animals, on the other hand, is isolated to a few specific organisms and is considered rare and unusual, especially amongst higher species of animals.
The most commonly known animals known to reproduce asexually are invertebrate animals such as aphids, flatworms, hydra, Bdelloid rotifers, ants, bees, parasitic wasps, coral and starfish. A small group of vertebrates that reproduce asexually as their normal method of reproduction incude a few specific species of whiptail lizards, Sonoran desert minnows, and brine shrimp. Other vertebrates that have been found to reproduce asexually, but in very rare or unique situations, are turkeys, sharks, komodo dragons, boa constrictors, and burmese pythons. In most of these cases of higher vertebrates, it is females producing more female offspring. The exception would be the turkey, which lays eggs that result in all male offspring.
There are a few ways in which an animal can reproduce asexually. The first method is known as parthenogenesis, which is also known as “virgin birth”. Parthenogenesis is when a female produces viable eggs or live young without ever having sexual intercourse with a male. This is the most commonly known method of asexual reproduction among the vertebrate species of animals, and most of the invertebrates as well.
The second method is known as polyembryony. Polyembryony is a form of asexual reproduction that is mainly used by invertebrate species of flatworms and involves the formation of multicellular propagules, or offshoots, that will develop into new flatworms.
Another method is known as fragmentation. Asexual reproduction by fragmentation occurs when a small piece of the adult organism breaks off and begins to grow on its own into a fully formed clonal version of its parent. This method is most commonly seen in invertebrates such as starfish and coral.
The last method is known as budding. Budding is when an organism forms a daughter organism that grows out of the mother and eventually separates from its mother. This type of asexual reproduction is found in the hydra, and other simple multicellular invertebrates.
There are two groups of animals that use parthenogenesis for reproduction. The first group are known as cyclical parthenogens which use both asexual reproduction and sexual reproduction. The second group are known as constant parthenogens which use asexual reproduction exclusively. Cyclical parthenogens include aphids, bees, and the Sonoran desert minnows. Constant parthenogens include the whiptail lizards, rotifers, and brine shrimp.
The animals that are considered higher vertebrates (such as the snake species, sharks, turkeys and komodo dragon) and have reproduced asexually are unusual and rare, as they use sexual reproduction as the main method of reproduction 99.9% of the time. In most cases, these animals were living in captivity and did not have access to a male to reproduce sexually. Asexual reproduction in these animals in the wild is most likely never going to occur.
