Amphibians are cold-blooded vertebrates that came to land about 360 million years ago.
Amphibians are usually classified according to their living environment, appearance structure, and so on.
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So far, more than 8000 species of amphibians have been identified, and some of these species are in danger of extinction. Amphibians need both water and land environments to live
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Below we will go into the species of amphibians, how amphibians breathe and the characteristics of amphibians.
Species of amphibians
How many amphibian species are there? Approximate numbers can be used to answer this question. So far, according to current research, it has not been possible to give a specific number.
Most amphibians live in two different stages in two different environments, water and land. But does this apply to all amphibian species? There are many amphibians that do not follow this life strategy.
As said, amphibians can be classified based on different factors. Here we discuss one of these divisions, dividing these animals into three categories based on their differences in appearance.
Caudal
Some amphibians that have an elongated and cylindrical body are called caudal. This type of amphibian initially has a bony skull, which is then eaten over time, becoming joints. This group of tailed animals has a long and developed tail. Mostly they move with the help of their tails and their tails are slightly larger than fish. Salamanders are a good example of this species.
In this species of tailed amphibian, the arms and legs are perpendicular to the body. You can see this type of amphibian in North America and often in northern and tropical regions.
Anura
Tailless amphibians, or Anura, are amphibians that use their hands or feet to propel themselves. These amphibians need water early in their life and can then live in a combination of both areas. All kinds of frogs, toads and other animals of this category are placed in this order.
Frogs and toads are the best-known tailless amphibians because of their geographic distribution. However, we often confuse frogs and toads. Frogs have soft, moist, and smooth skin and live near water, and toads have rougher, drier skin that is better adapted to the dry environment.
Tailless amphibians are not good swimmers because their bodies are not spindle-shaped. And their movement on land is also a kind of jump. And it is biologically inferior to other vertebrates.
Apoda
Apoda amphibians are one of the naturally occurring amphibian species. These amphibians are also called Caecilians. In this category of amphibians you will see animals that are like worms or snakes.
These burrowing and worm-like animals have a narrow, elongated body with annular grooves that reach up to half a meter in length. They are placed in the holes they dig in the ground, their eyes are inactive, and they feed mainly on earthworms.
Characteristic of amphibians
Among the common features of the above three categories, we can mention shell less eggs, gas-permeable skin, adult carnivores, ritual mating, and their relatively even distribution.
One of the very interesting features of some amphibians is their skin. They can breathe through their skin, and they also excrete a substance through their skin that keeps them constantly moist.
Amphibian skin is permeable to water and gas exchange can occur, allowing adult amphibians to breathe without rising to the surface and hibernate in deep ponds. In amphibians, mucous glands have evolved and are mainly located on their head, back and tail. The secretions produced by these glands help to keep the skin moist.
Most amphibian species have glands that secrete toxins. These amphibians secrete a substance from their skin that makes it impossible for the hunter to get to them in many situations. The spots that can be seen on the skin of many salamanders is why you can spot them because this type of salamander is very poisonous.
Parotid glands, noroxin and bufotoxin are responsible for venom production in these animals. These glands are found behind the ears of toads, along the backs of frogs, behind the eyes of salamanders, and on the upper surface of the blind of salamanders.
Amphibian skin color is created by three layers of pigment cells called Chromatophores. In many species, the color change is caused by hormones secreted by the pituitary gland.
How many amphibian species are there? It should be better answered with a percentage. It is interesting to know that 90% of the different amphibian species are frogs.
Circulatory and Breathing system
The circulatory system in amphibians is divided into two stages: adolescence and adulthood
When young, blood flow is similar to that of a fish. The double-chambered heart sends blood to the gills to be oxygenated, and in a single circuit, the blood circulates throughout the body and returns to the heart. In adulthood, amphibians lose their gills and develop lungs.
Amphibians have a heart composed of a single ventricle and two atria. When the ventricles begin to contract, deoxygenated blood is pumped to the lungs through the pulmonary artery. The continuous contraction pumps oxygen-rich blood to the rest of the body. Mixing of the two blood streams is minimized by the anatomy of the lumens.
The rate of diffusion of oxygen entering the blood in amphibians is relatively slow.
Amphibians can breathe in three different ways. As we mentioned earlier, depending on their location, amphibians can use lungs on land and gills in water to breathe, and some hibernating amphibians breathe with their skin.
Amphibian defense system
Like other animals, amphibians have methods of defense. It is interesting to know that these animals show amazing behaviors to care and defend themselves.
One of the simplest ways these animals can defend themselves is by producing venom in their bodies, some of which shed this venom through their skin.
Another type of non-venomous amphibian urinates to keep the predator away from them. The urine of these frogs has a very bad smell and causes the hunter not to approach them.
These animals, like others, can easily lead to the death of people. In fact, Agin’s poison frog is a species of amphibian that can kill 10 people with a small amount of poison. This is very dangerous for people who are closely related to these animals and they can easily lose their lives.
Amphibian skeletal system
Amphibians have different skeletal structures because they are different species and each of them has a different skeletal structure. Amphibians that have arms and legs move with them. Some jump and some run. Tailed amphibians also move with their hands and feet.
Both of the species we mentioned also swim with their hands and feet in the water, although the tailed type also uses its tail for swimming. Finally, there is the Apoda group, which moves by crawling.
How amphibians mate
Finding a suitable mate is the first step to starting amphibian breeding. Therefore, it is possible that there may be a conflict between males over ownership of a female, or males may begin to perform instinctive movements and show themselves to attract the attention of the female pair. This act is called courtship.
How many amphibian species are there due to reproduction?
Breeding site, clutch structure, oviposition site (water or land), larval development, and parental care create reproductive traits in amphibians.
In vertebrates, fertilization occurs both internally and externally:
- In external fertilization, the female animal usually releases her eggs into the water, and the male fertilizes them by pouring his sperm onto the mass of eggs.
- In internal fertilization, the male animal usually injects his sperm into the female’s reproductive organs. In internally fertilized amphibians, the male stimulates the female by secreting substances from his tail. The male salamander takes a capsule filled with sperm from the body and directs the female towards it. The female salamander enters the capsule with its cloacal lobes.
Amphibians can be oviparous, Ovoviviparity and viviparous.
- oviparous: After internal or external fertilization and after laying the ovum, the mother removes the ova from her body (depending on the species and environmental conditions, as well as the degree of temperature and humidity) and the ova remains in the environment for some time until the ova matures. The embryo is created in the egg and its development is complete.
- Ovoviviparity: In some species of amphibians and reptiles, the egg is held in the mother’s body after formation, and the baby hatches before, at the same time, or immediately after the egg is laid.
- Viviparous: In this method, which is found only in some types of internal fertilization, after its formation, the ovum is placed in the fallopian tube and all stages of growth and development of the embryo are carried out in the mother’s body. Babies are born after full term along with the amniotic sac. Such as the alpine salamander and the African live toad.
How many amphibian species are there?!
Based on what we said earlier, there are more than 8000 amphibian species, some of which are endangered.
More than 2400 species are threatened with extinction and more than 160 species have become extinct so far.
Meanwhile, Brazil has the most amphibian species in the world with 811 described species. It is interesting to note that America has only 292 amphibian species covering an area almost the size of Brazil.
FAQ about amphibian species:
- How do amphibians move?
Amphibian locomotion varies by species. Each species has different organs of movement.
- How are amphibians classified?
Corresponding to the different species of amphibians, these animals are divided into three categories based on their appearance.
- Are amphibians dangerous to humans?
Some amphibians can cause human death due to their defense system.
- How does amphibian reproduction work?
In amphibians, fertilization occurs both internally and externally, depending on the species.
- What is the defense mechanism of amphibians?
As you know, amphibians have different defensive behaviors depending on the species; some of them defend themselves by producing poison in their body.
- How many amphibian species are there?
Different sources report the number of amphibians differently, and the largest number of amphibians identified so far is more than 8000 species.