20 FASCINATING ASEXUAL ANIMALS AND THEIR CHARACTERISTICS - ENVIRONMENT - 2024

A collection of asexual animals whose reproduction requires only one parent, and which results in the offspring being genetically identical to their parents due to the fact that there is no fusion of gametes. That is, they are clones.

Here is a list of 20 animals that reproduce asexually:

Top 20 most impressive asexual animals

1- Marbled crab

These types of crustaceans, which look like tusked shrimp, are an asexual form of crayfish that live in Florida and southern Georgia.

The marbled crab is an invasive species that has established populations in three countries at the same time greatly altering native wildlife. Many jurisdictions regulate the importation and release of various types of crayfish. In 2011, Missouri added marbled crabs to its banned species list.

Marbled crabs perform asexual reproduction through apomixis, a process normally reserved for plants in which an organism can generate an embryo without fertilization.

2- Whip-tailed lizard

Cnemidophorus of the family Teiidae. This type of lizard is only female. They generally perform a type of pseudo-copulation where two females pretend to have sex as if they were a man.

Although not strictly necessary to reproduce, this simulated sex has been shown to increase the fertility of lizards in particular by acting on copulation and producing more eggs than those that do not.

The lizard that simulates the female role will produce larger eggs than the one that acts assuming the male role.

Even though there is no external fertilization, the lizard's descendants are not actually perfect clones of each other. Rather, recent research has shown that the New Mexico whiptail lizard produces twice as many chromosomes as other types of lizards.

"Parthenogenesis" is the technical name for the reproduction of the whip-tailed lizards of New Mexico. It comes from the Greek "parthenos", which means "virgin", and "genesis", which means "birth." Parthenogenesis is the virginal development of the ovules, without previous fertilization.

3- Komodo Dragonas

Varanus komodoendis. This type of lizard, the largest in the world, can reach a little more than 3 meters and it has recently been shown that females can reproduce without being fertilized by a male.

This phenomenon was discovered in two captive dragonflies in two London zoos that fertilized themselves as father and mother to their young.

Of the eggs of this type of self-fertilization, only eggs with male genes emerge. This discovery is significant as Komodo dragons are in danger of extinction and there are only about 4,000 left on the entire planet.

It can then be determined that through parthenogenesis, Komodo dragons can perpetuate their species, establishing an active population in which they can reproduce sexually and preserve the spice.

4- Sharks in captivity

Sharks that live in captivity, though only rarely, reproduce asexually. Female hammerheads captured as pups and kept away from males in Florida, United States, were the first to reproduce asexually.

The asexual reproduction that occurs in hammerhead sharks is also known as parthenogenesis. It refers to the female's ability to create and maintain baby shark without a male shark and without ever having mated.

This has only been seen in captive shark cases, but can occur in the wild where there is a severe shortage of male sharks. Although this phenomenon is extremely rare, asexual reproduction has been observed in several confined sharks.

Following the discovery of the cub shark, extensive testing (including paternity testing) was conducted. Some females were confirmed to have never had contact with any other shark, and the possibility of sperm retention from previous encounters was ruled out.

5- Hydra

The Hydra is a cnidarian. An exclusively freshwater organism and there are many different species of Hydra. It is relatively small, only half a centimeter long on average.

The Hydra has a tubular body, a "head" at the distal end, and a "foot" at the proximal end. They use this foot to stick to rocks or the underside of plants.

They have a ring of tentacles to collect food around their head. The Hydra only has ectoderm and endoderm (no mesoderm). Hydras generally reproduce asexually. The asexual reproduction of the hydra generally occurs in environments with an excess of food.

The first step in the reproduction of asexual hydra is the beginning of the bud, during this process, the first signs of an outbreak begin to show. Then the tentacles begin to grow and the mouth of the new hydra begins to develop. After the separation of the new hydra begins, the separation of the bud from the original hydra occurs.

Later the detachment of the New Hydra occurs. This is the final step in the asexual hydra reproduction cycle, in this step the new hydra detaches from the mother, creating a completely new hydra, this new hydra is generally 3/5 the size of the new hydra.

6- Wasps

Asexual reproduction of wasps is complicated. When certain species are infected with the Wolbachia bacteria, the chromosomes in the wasp eggs change. As a result, the eggs do not divide, and instead of creating single offspring, the wasp mothers create female clones of themselves.

While it sounds like a neat survival hack, the wasps are only buying time. Ultimately, the bacteria create only infected female clones. Wolbachia is a bacterium that lives within the ovaries and testes of many arthropod species, wreaking havoc on sex lives and gender proportions.

In wasps, the Wolbachia has completely eliminated the males, causing the ovum to develop as a female.

In wasps, the infection appears to be innate; In the laboratory, the bacteria could not be transferred between the wasps. That led the researchers to speculate that the wasp and its parasite could be a species in cospeciation, an event that occurs when a symbiotic relationship between two organisms leads to a change and creates a new species in the process.

Whenever a wasp lineage diverged into two species, a new strain of Wolbachia develops in each isolated wasp species.

7- Starfish

Starfish (scientific name Asteroidea) are the main group of echinoderms. There are about 2,000 species of starfish living in the world's oceans in tropical coral reef habitats, kelp forests in the deep and cold oceans. All starfish are marine animals.

Starfish can reproduce sexually and asexually. In sexual reproduction, fertilization occurs in water with males and females releasing sperm and eggs into the environment. Fertilized embryos, which are free-swimming animals, become part of the zooplankton in most species.

Eventually the larvae undergo metamorphosis, settle to the bottom, and grow into adults. Some species cover their eggs, either simply by sitting on them, or by using specialized baskets.

Asexual reproduction is by fragmentation, part of an arm and part of the central disk separating from the "parent" and becoming an independent individual starfish.

In the past, many starfish have been exterminated by cutting them into pieces, but starfish have been able to regenerate and become more starfish.

8- Blind shingles

Ramphotyphlops braminus is a very common, but rarely seen, species that spends much of its time burrowing through the ground and litter.

They can be found when digging in soil, turning logs or rocks, or after a heavy downpour when they are forced to the surface of the ground. This is one of the smallest snakes in the world, rarely exceeding 20 cm in length.

The body is dark brown to black throughout. The head is barely perceptible from the body, and the tiny eyes appear as black dots. Virtually blind this snake can, however, distinguish between light and dark. The tail is short and blunt and has a short, sharp spine.

The Brahminy blind shingles feed on small invertebrates, mainly ant larvae and pupae. It is one of the only two species of snakes that reproduces by parthenogenesis and fragmentation, that is, all specimens are female and their reproduction is asexual.

According to the Virtual Encyclopedia of Spanish Vertebrates, and according to Das and Ota (1998), Pellegrino et al. (2003) or Arias (2012):

"The evolution towards parthenogenesis in this and other reptiles seems to have its origin in the crossing between individuals of well differentiated species, in such a way that part of the diploid hybrid females thus generated would lose the ability to reduce the number of chromosomes in the oocyte during meiosis. When diploid ovules are fertilized by haploid sperm, they finally produce triploid females capable of reproducing without the need for males, but generating only their own clones ”.

9- Sea anemones

Depending on the species, sea anemones reproduce sexually or asexually. During sexual reproduction, eggs and sperm are released through the mouth.

Asexual reproduction occurs through longitudinal fission, binary fission, or pedal laceration. Sea anemones do not have a larval form, but instead develop an egg that, once fertilized, turns first into a planula and then into a sedentary polyp.

In sea anemones that reproduce sexually, some species have separate sexes, while others are protandric hermaphrodites, which are males that later transform into females.

Sea anemones that reproduce asexually through longitudinal or binary fission divide in half along their length to form two fully formed individuals.

When sea anemones reproduce through pedal laceration, pieces of their pedal disk break off, settle down, and grow into new anemones. Because sea anemones are mostly sedentary, parents and offspring grow close to each other, forming colonies that sometimes live and grow for decades.

10- Sea urchins

Sea urchins are echinoderms, a strictly marine group of invertebrates. Its reproduction can be asexual and sexual reproduction.

The asexual form of reproduction in sea urchins is a process known as fragmentation. This is when the body of an animal is divided into two or more parts, and both of them become individual animals.

11- Sea cucumbers

Crinoidea, phylum Echinodermata. These animals reproduce sexually and asexually like all echinoderms.

Asexual reproduction in sea lilies generally involves dividing the body into two or more parts (fragmentation) and regenerating the missing body parts. Successful fragmentation and regeneration require a body wall that can be torn and an ability to seal resulting wounds.

Successful regeneration requires that certain parts of the body be present in the missing parts.

13- Sea sponges

According to the University of Wisconsin La Crosse, sponges can reproduce asexually through external budding (or internal budding) and the regeneration of broken pieces that become full-body sponges on their own.

Sponges can also reproduce sexually. The external budding method of asexual reproduction involves an immature young sponge that forms at the outer base of the sponge. These buds can separate completely and become a separate sponge, or they can stay close to your sponge to form a sponge colony.

According to the University of California at Berkeley, the gemmule method of asexual reproduction is most common for sponges. Gemmules are essentially a bundle of inner buds in the form of cells that are housed within a protective coating.

They can be released when the parent sponge dies, usually due to poor conditions, including seasonal cold. The gemmules can then exist within the protective package until conditions improve, at which point they establish and mature into sponges.

Finally, because sponges have regenerative powers, particles that separate from an established adult sponge can eventually become a living sponge. The sponge from which the particle was broken will regenerate your tissue to replace the lost piece that is now turning into a new sponge.

14- Amoebas

According to Jennifer Welsh of Live Science, amoebae reproduce asexually through a process called binary fission.

This refers to the act in which the nucleus of a cell is stimulated to divide into an equal and exact replica of itself within the same cell walls, after which the two nuclei separate into their own individual cells, resulting in two Sovereign but genetically identical amoebae.

15- The loach, sand dollar or sea biscuit

Leodia sexiesperforata. Sand dollars reproduce sexually and asexually. The female sand dollars distribute the eggs in the ocean water while the males float nearby.

The male sand dollar expels the sperm onto the eggs to fertilize them. The fertilized eggs float out to sea, hatch into larvae, and eventually settle to the bottom of the sea where they continue their life cycle.

Sand dollars are marine invertebrates that belong to the echinoderm family. This family also includes brittle stars, sea urchins, and sea cucumbers.

Spiny echinoderms, such as starfish and urchins, can reproduce asexually by rejuvenating or reproducing damaged limbs and spines. Since sand dollars are rounded animals without spiny arms, they can rejuvenate the damage done to their body structure asexually.

Male and female sand dollars are identical with no distinguishable markings to identify their sex. Researchers from the United States National Library of Medicine report that sand dollar Dendraster excentricus larvae clone when predators are nearby.

This means that sand dollar larvae have the ability to reproduce asexually when threatened in an attempt to protect and propagate their species. The cloned larvae are much smaller in size than their original counterparts, making them difficult for predators to detect.

For larvae to clone, their environmental conditions must be favorable for growth and reproduction.

16- Planarians

Planarians are capable of reproducing sexually or asexually, depending on the species and the breeding circumstances. Planarians are hermaphrodites and mating consists of partners exchanging sperm with each other before setting off to lay eggs.

Despite the similarity of planarian sexual reproduction to that of other animals, planarians are capable of asexually reproducing by binary fission. This mechanism takes advantage of the extreme ease of the planarians to regenerate the lost sections of their bodies.

Once the planarian divides in half - a division that can occur along any axis of its body: latitudinal, longitudinal, or coronal - each section of the body activates special cells called neoblasts.

Neoblasts are adult stem cells that can divide into new cell lines that then specialize in all tissues in the body. The neoblasts at the site of the rupture begin to generate new tissue to replace the structures that each half has lost, resulting in two new flatworms.

This process of reproduction through the division of the whole body can occur as a result of traumatic injury, or it can be initiated by the planarian itself as a normal process called transverse fission. When the planarian begins the process, its body is divided latitudinally between the head and tail sections.

17- Paramecium

Paramecium reproduces sexually and asexually. Asexual reproduction takes place by the binary fission method. First, the micronucleus divides into 2 nuclei by mitosis. The macronucleus divides into 2 by mitosis.

The citpharyngeal is also divided into 2 parts. The cytoplasm is also divided into 2 parts. Then the transverse constriction is made of two sides. New contractile vacuoles are formed. The constriction meets in the center and two paramecia daughters have reproduced.

18- Water fleas

Daphnia pulex. Water fleas reproduce asexually and sexually and have a cyclical parthenogenetic life cycle, exhibiting heterogeneous reproduction. In asexual reproduction, the females produce diploid eggs that develop into exact clones.

Only females are produced during asexual reproduction cycles. However, during adverse conditions (low food availability, extreme temperatures, high population density), this species reproduces sexually.

During sexual reproduction, males latch onto females using their specialized second antennae.

19- Scorpions

Scorpions are arthropods, arachnids. Within scorpions there are 13 families that comprise more than 1,700 different species. Some species reproduce asexually, but most of the scorpion's reproductive cycles have only one basic pattern.

Parthenogenesis is a rare phenomenon in scorpions, and can be observed notably in the species Tityus serrulatus Lutz & Mello from Brazil, Tityus columbianus (Thorell) from Colombia and Tityus metuendus Pocock from Peru and Brazil. Parthenogenesis of the Thelytokous (with all female offspring) is seen more frequently.

20- Salamanders

Some salamanders of the genus Ambystoma have been found to reproduce asexually by a process called gynogenesis. Gynogenesis occurs when sperm from a diploid male stimulates the development of a triploid female egg, but never incorporates into the new zygote.

In the gynogenesis of this type of salamanders only composed of females, the ovum requires activation by a sperm to initiate its division and development, but previously it must duplicate its genetic material through an endomitosis process to avoid the formation of unviable haploid zygotes..

References

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   Reference.com. (2016). How do sand dollars reproduce ?. 1-24-2017, from IAC Publishing, LLC.

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