Do All Animals Reproduce? Explore Unique Facts About Asexual Animals

Rajnandini Roychoudhury
Jan 30, 2023 By Rajnandini Roychoudhury
Originally Published on Oct 22, 2021
Edited by Luca Demetriou
Fact-checked by Nishtha Dixit
A Crown of Thorns Starfish.
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Age: 3-18
Read time: 10.1 Min

It is astonishing to think that there are species who reproduce asexually and their offspring inherit their genes without any gametes fusion.

We may have come across that single-celled and prokaryotic organisms reproduce asexually. However, asexual reproduction exists even in invertebrates in the form of parthenogenesis.

Parthenogenesis is a form of asexual reproduction where the embryo develops by fertilizing the eggs without the male sperm. Sexual reproduction is the phenomenon when the eggs are fertilized by the male sperm however in asexual reproduction this phenomenon is absent. Nevertheless, some species can shift between parthenogenesis and sexual reproduction they are called facultative parthenogenesis. Sexual reproduction enables haploid chromosomes while the consequence of parthenogenesis is diploid chromosomes. The offspring reproduced by the female primarily has all the maternal alleles and are called clones. The offspring that inherits half of the maternal chromosomes are called half clones. Other modes of asexual reproduction other than parthenogenesis include fragmentation, budding, and binary fission mainly. Fragmentation is a type of asexual reproduction in a multicellular organism where the fragment of body parts splits and forms another identical organism. This phenomenon is common in starfish and annelid worms. Budding is a process where offspring generates from the bud-like structure which is common in echinoderm larvae, corals, and Convolutriloba, which is a type of flatworm. Various organisms such as amoeba, cyanobacteria, eubacteria reproduce asexually and their process is called binary fission. The greatest disadvantage of this kind of reproduction is that as it occurs without fertilization and the offspring is genetically identical, which makes it more susceptible to diseases.

In this article, we have discussed more asexual animals so keep reading also check out the fun facts about Crown-Of-Thorns Starfish Facts and armored animals.

What type of animals use asexual reproduction?

Reproduction in animals can occur in two ways sexually and asexually. While most of the organisms reproduce sexually some organisms are known for asexual reproduction.

The process of involvement of the female egg cells with male sperm is how sexual reproduction in animals occurs. However, in the case of asexual reproduction particularly in parthenogenesis, there is no requirement of the male sperm. Although the process of parthenogenesis is observed in various vertebrate species yet it is common in invertebrates like aphids, ants, wasps, and bees. The Cape honey bee of South Africa can reproduce by laying eggs that are fertilized without a male. The process of thelytoky enables the worker bees to lay diploid female eggs. However, only workers with thelytoky phenotype can undergo the process of thelytoky. Aphids also follow a similar reproductive pattern of thelytoky which is a sort of parthenogenesis. Aphids can also alternate between asexual and sexual reproduction. There are wasps whose chromosomes in eggs change when infected by Wolbachia bacteria. Thus, female offspring are just the clone of their mother as the eggs do not divide. Several vertebrates exhibit the form of asexual reproduction even though the majority of them reproduce sexually. Mention should be made of the whiptail lizard or race runners of South America and Mexico that are solely identified as unisexual reptiles. The whiptail lizard reproduces by the process of parthenogenesis and its fertilized eggs are genetically identical. So the offspring is a clone and can reproduce by parthenogenesis. When it comes to asexual reproduction Komodo dragons are a crucial part of this system. Komodo Dragons that happen to be a native species of Indonesia possess the ability to produce eggs because of the presence of two sex chromosomes. These sex chromosomes can multiply on their own. The presence of W and Z chromosomes in a Komodo dragon will either give birth to a nonviable male or female. Parthenogenesis was observed in sharks for the first time in 2001 when a female shark gave birth to a female shark without fertilization. Few species of starfish can reproduce by fragmentation. It has been observed that the starfish can grow and develop from an existing fragment. The portion of the body that splits up also regenerates. Out of 1800 species of starfish, only 24 species can asexually reproduce.

How many species of animals are asexual?

Some species are asexual while others can alternate between asexual and sexual reproduction. The exact number of such species is not listed however it is over 2000 thousand.

Asexual reproduction in eukaryotic plants and fungi can occur by the process of fission, vegetative propagation, budding, and spore formation. In the species of animals, it is primarily parthenogenesis and fragmentation in the case of starfish. When the scope of sexual reproduction is limited many species including bees, sharks, whiptail snakes, and other organisms resorts to Parthenogenesis. However, there can be various types of parthenogenesis including facultative parthenogenesis, and obligate parthenogenesis. While heterogony, where females can shift between sexual and asexual reproduction, is a form of facultative parthenogenesis. Gynogenesis is an aspect of obligate parthenogenesis. The genetic variation in these organisms is limited or none. Nevertheless, the absence of the concept of sexual reproduction is sparse in animals. Sexual reproduction may lead to genetic diversity and asexual reproduction leads to immediate population growth. Despite that species like the Komodo dragon are endangered.

What are some examples of asexual animals that are invertebrates?

Invertebrates refer to those species which do not have a well-developed or any sort of vertebral column. There are several insects and marine organisms that belong to this category. Some of these invertebrates species are asexual that we are going to discuss below.

Many species of phasmids or Phasmatodea that is a group of stick insects give birth even if they do not mate. The reproduction is parthenogenic, its offspring is female and the clone of its parent is with no genetic variation. The non-hybrid stick insects are the result of facultative parthenogens while the hybrid stick insects are the result of obligate parthenogens. Just like stick insects, few species of ants can be both sexual and asexual. The fertilized eggs of the black carpenter ant become female workers while a male evolves from unfertilized eggs. The fungus-growing ant species Mycocepurus smithii of Latin America reproduce asexually by thelytokous parthenogenesis. It was found in research that most of the females were a clone of the queen while an insignificant amount of them has blended genes as a result of sexual reproduction and fertilization. The Wolbachia bacteria-infected eggs of the wasps change in chromosomes is evident. While in some species of wasps the fertilization of eggs leads to females while the unfertilized eggs lead to males in other species the eggs are fertilized by the female wasps solely. The Cape honey bee is another example of an invertebrate that reproduces asexually. It is mysterious as to why the honey bee population in South Africa is reproducing asexually. These species of honey bees have the potential to invade the nest of other honey bees and reproduce in the same manner. The eggs are fertilized by the own DNA of the female worker bees. Other than these invertebrates the marine invertebrate that can reproduce asexually is the water flea. The water flea can be found in lakes, ponds, and other shallow water bodies. It is an aquatic crustacean that sustains on microscopic organic substances. Water fleas mate sexually occasionally however they reproduce asexually, principally this process is called cyclical parthenogenesis. Water fleas have another peculiar characteristic when threatened they mate and reserve the eggs that can remain inactive for many years. These eggs have genetic variation as a result of DNA exchange between males and females. Hydra is another freshwater invertebrate that reproduces by budding. The formation of bud on the body of the hydra grows and separates when mature.

European honey bee on an apricot tree.

What sea animals use asexual reproduction?

Asexual reproduction has been observed in sea animals. Some of the sea animals may include big fish species like Hammerhead Shark, Blacktip shark, Zebra Shark, Starfish, sponges, Sea anemones, and others. So let us learn about the asexual mode reproduction of these sea animals below.

The notion of virgin birth in Hammerhead sharks was first observed by a team of scientists in 2001. The female hammerhead shark was in captivity, therefore it couldn’t come in contact with any males. Even after that, the female shark was successful in reproducing which shocked everyone. Knowing the fact that female sharks can store male sperm for years tests were run to confirm whether it is true or not. However, it was found that the offspring had no male DNA. Reproduction occurred due to parthenogenesis and the offspring had no genetic variation. The Blacktip shark is another instance of automatic parthenogenesis. The reproductive system of the female produces an egg along with three polar bodies. The polar bodies are reproductive cells and act as sperm, usually, these polar bodies are absorbed by the body. However, when the genetic material of the polar bodies is the same it causes fertilization of the egg without mating. Other sharks like the Zebra shark may reproduce asexually by parthenogenesis. Marine organisms like some species of Starfish reproduces by fragmentation or fission. This is a phenomenon where reproduction does not involve fertilization of any kind by split and regeneration of the body part. This may sound very similar to budding but these two are separate phenomena. The existing starfish voluntarily splits a part of its body and this fragment grows and develops into a new organism. Approximately 24 varieties of starfish can achieve fission or fragmentation and reproduce asexually. Just like most organisms sponge reproduces either sexually or asexually. Sponge reproduces asexually either by gemmulation or budding. Gemmules are mainly the internal buds of sponges that enable the development of new organisms from the existing parent. Sea anemone reproduces asexually particularly in shallow water but in the deep sea, it inclines toward sexual reproduction. This sea organism retains the ability to stretch itself and then split up from the middle to form another anemone that is of identical size. This phenomenon of splitting up from the center is also called longitudinal fission.

What asexual animals use budding?

Budding is a process of the development of a new organism or offspring from the existing parent. Though budding is a common practice in both plants and asexual animals this occurrence is largely different from each other.

Hydra is one such organism that reproduces by budding. Due to continuous cell division in a particular spot, it gives rise to another organism until completely developed. Once the new hydra that is attached to the body of the existing hydra is developed it detaches from its body and forms a new individual. Some flatworms likewise reproduce by budding. Flatworms are unsegmented and devoid of any proper respiratory system. The flatworms generate self-fertilizing eggs. This egg further develops into new flatworms. Sponges as stated earlier are known for asexually reproducing by budding or gemmulation. The Sea anemone is known to stretch themselves and split longitudinally and produce the exact copy of themselves.

What are the disadvantages of asexual reproduction?

In all the above-mentioned paragraphs we have learned about asexual animals and their mechanism. However, learning about the disadvantages of reproducing is equally important.

The biggest advantage of the asexual mode of reproduction is that there is no scope to mate which leads to a rapid boost of the population of the animals. This process is faster than sexual reproduction and it involves only females as males play no active role. However, on the other hand, though the population is boosted up yet the genetic variation is absent. The absence of genetic variation makes the offspring more susceptible to various diseases. It also makes them incapable to adapt to a different habitat. The offspring also inherits the genetic defect or mutation as its parent because it is the clone. The chances of extinction are more because every single offspring as a result of cloning will have the same weakness. As the population increases rapidly it is hard to control the population of a certain organism like the Marbled crayfish.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions forDo All Animals Reproduce? Explore Unique Facts About Asexual Animals then why not take a look at Amazing Facts For Birds That Are Blue: Scrub Jay And Many More!, or Are Holly Berries Poisonous? And How To Prevent Dogs From Eating Them?

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Written by Rajnandini Roychoudhury

Bachelor of Arts specializing in English, Master of Arts specializing in English

Rajnandini Roychoudhury picture

Rajnandini RoychoudhuryBachelor of Arts specializing in English, Master of Arts specializing in English

With a Master of Arts in English, Rajnandini has pursued her passion for the arts and has become an experienced content writer. She has worked with companies such as Writer's Zone and has had her writing skills recognized by publications such as The Telegraph. Rajnandini is also trilingual and enjoys various hobbies such as music, movies, travel, philanthropy, writing her blog, and reading classic British literature. 

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