The Amphibian classes Most important that exist today are divided into three large groups: the order Anura, order Caudata and order Gymnophiona.
Amphibians are vertebrates that are characterized because their breathing system undergoes a modification throughout their life. It starts being Gill (Through the bronchi) in the larval stage, and pulmonary (Through the lungs) in the adult stage.
The word amphibian comes from the Greek"amphibia"meaning"both lives"or both types of life, making clear reference to this capacity of breathing that allows them to live both in water and on earth.
Although these animals spend most of their life on land, they are born in the water, they return to lay their eggs and are able to be submerged for a long time thanks to which they can Breathe through the skin .
The skin of amphibians is not covered by hairs or feathers like other vertebrates, but is totally naked and also has large numbers of glands that secrete a slimy substance that keeps them permanently moist, even out of the water.
They are said to be the oldest vertebrates on Earth and have undergone a very slow evolution over millions of years, during which a large number of specimens have disappeared. Today, it is estimated that there are more than 6,300 species of amphibians in the world.
Main classes of amphibians and their characteristics
The groups of amphibians mentioned above are explained in more detail below:
1- Anurans (toads and frogs)
In ancient Greek, Anuro means"without tail"and it is precisely this that characterizes this group and differentiates it from the rest.
The body of these species is short and wide and their hind legs tend to be more developed than the forelegs, making them stand out for their ability to make big jumps.
The size of amphibians in this group can vary from truly small (less than one centimeter) to some more than 30 centimeters in length, such as the Goliath frog, the largest in the world.
This is the most diverse and diverse group of amphibians and it is estimated that there are more than 5,400 species, although it is also true that many have become extinct or are in Danger of extinction .
While frogs and toads belong to different families ( Pelophylax Y Bufonidae , Respectively), both terms are often confused, reclassifying them in a rather arbitrary and unscientific way.
In this way, frogs are classified as those amphibians with smooth and moist skin that live mostly in the water, the toads being, according to this view, those of rougher and darker skin, fatter and slower and seen with Higher frequency in wetland.
Other characteristics of anurans
1- Large heads and wide mouths.
2- Salping and eyelid eyes.
3- Protractile tongue (projecting outwards).
4- Four fingers on the front legs and five on the hind legs.
Interdigital membrane.
2- Caudates (salamanders and newts)
Unlike anurans, the caudates do have a prominent tail which, together with their rough skin, which in some cases imitates scales or changes color, give it a somewhat prehistoric appearance.
They have elongated bodies with flat and wide skulls. Its size can vary between 30 centimeters and the meter in length, as the case of Japan's giant salamander, the largest known so far.
A few species of salamanders have internal fertilization, contradicting the common amphibians.
Also, a minimal part of the approximately 550 existing species inhabit the Southern Hemisphere (North of South America), since the great majority lives in the Northern Hemisphere, specifically in the United States of North America.
Caudates can become confused by the common people with lizards, but differ from these in that they do not have scales.
Other characteristics of the caudates
1- They have 4 short legs and generally the same, although in some cases the later ones are less developed or almost nonexistent.
2- They have teeth in both jaws.
3- They can regenerate a mutilated member, such as the tail.
4- They have no middle ear (another difference with respect to anurans).
5 - Larvae have a very similar shape to adults.
3- Gymnofiones or apodos (cecilias)
Gymnophiona Means"naked head"in Greek and is the least diverse group among amphibians.
They are characterized by their worm form (vermiformes) and protractile tentacles, one on each side of the head, where their sense of smell resides, essential for food, since their eyes are very small and their eyesight is limited or null .
They have no limbs or waist, and they inhabit only the very humid regions of the tropics, usually under the ground or directly under water. They are popular in India, Southern China, Central and South America. They do not exist in Europe or Oceania.
Their size can vary from 1 centimeter to one and a half meters in length, along which some 200 vertebrae in the form of rings are aligned, a very primitive skeletal structure.
Some are oviparous and others viviparous (eggs are incubated inside the female's body) with internal fertilization.
There are approximately 200 known species of cecilia. From their appearance, they are often confused with earthworms.
Other characteristics of gymnophies
1- Flat head and rudimentary eyes that sometimes remain closed.
2- Small teeth and jaw located under the head.
3 - Solid skull that makes it easy to dig under the earth.
4 - Wavy displacement, thanks to its ring structure.
5. They are carnivorous; Depending on the size, can get to eat snakes and other amphibians.
Other general characteristics of amphibians
1- They have legs instead of fins.
2- Naked and moist skin.
3 - They are animals of cold blood, that is to say that their body temperature adapts to the one of the means in which they are.
4- Gill respiration when they are larvae and pulmonary when they are adults.
5 - They are carnivorous (they feed on invertebrates like insects, crustaceans or arachnids).
6- They are oviparous.
7- Its fertilization is external (the eggs are put in the water) in most cases.
References
- Amphibians. Recovered from biodiversity.gob.mx.
- Amphibians. Recovered from portaleducativo.net.
- Anura. Amphibian Order. Retrieved from britannica.com.
- Nature. Caudata. Retrieved from diarium.usal.es.
- Caudata Scopoli. 1777. Recovered from asturnatura.com.
- The Cecilias. Retrieved from bgreenproject.wordpress.com.
- The cecílidos or cecilias. An amphibian without legs that is confused with the worm. Retrieved from paxala.com.
- Amphibia, Caudata and Gymnophiona. Retrieved from wikipedia.org.