What are amphibians?

Amphibians are the vertebrates that live both on land and in water. Amphibians are ectothermic organisms that need to be in a suitable environment otherwise their body temperature will vary according to the outside environment. There are three main orders of amphibians; Anura, Caudata, and Gymnophiona.

What are the three main orders of amphibians?

Following are the three main orders of amphibians:

The first one is the Anura, which includes the frogs and the toads:

Frogs

Frogs have many species around the world:

• The first one is the California red-legged frog. This frog is found in California and Mexico and can be seen rarely in other states. It is called such a name because of the red color underneath the legs and belly. Moreover, it has brown or gray colored heads and black spots or large black blotches on the back that extend to the hind legs. The male calls the female for breeding in the form of short grunts and then makes a last loud growl. The female lays eggs on the ground, and the male fertilizes them leading to the hatching of eggs, and young ones are born.
• The second is the tree frogs having terminal phalanx shaped into claws. They have toe pads to climb the trees. Not all frogs belonging to this family climb trees. This family of tree frogs has 800 species. The body of tree frogs have brown, gray, or black color. They munch on insects and plants mainly.

Frogs VS toads

Frogs and toads are different species but look much like each other. Frogs have moist skin and longer limbs than the size of the body. On the other hand, toads have shorter limbs and dry skin. Toads crawl on the ground while frogs hop to go from one place to another.

Toads have parotid glands that can secrete poisonous chemicals called bufotoxins, which can cause the death of small animals and allergic reactions in humans.

The second one is the Caudata, which includes salamanders and newts:

Salamanders

Salamanders have many species in the world:

• The first is the tiger salamanders, which can dig their burrows about 2 feet deep. They usually live in it most of the time and are rarely seen. They have dark gray, black, or brown bodies having brownish-yellow stripes or spots. They are mainly found in New York and Florida. Males move to breeding ponds and call females. The female lays eggs after 2 to 3 days in a pond and eggs hatch after 4 weeks. Larvae stay in the pond for 2.5 to 5 months and then go out.
• The next type of salamander is the spotted salamander, which has a dark gray or black body having orange color spots. They live in the eastern part of the United States. Spotted salamanders have narrow heads smooth skin and gray bellies underneath. The eggs of the female sometimes have green algae which converts the carbon dioxide produced by the newborns to oxygen in the egg shells.

Newts VS lizards

Newts are not lizards as most people think. Newts are not reptiles, move more slowly, and have no scales. They also lay eggs in water while lizards do not lay eggs in water. Newts have very thin skin through which most of the gaseous exchange takes place.

The third one is the Gymnophiona which includes caecilians or limbless amphibians. These amphibians are the food of most of the reptiles.

What is the anatomy and physiology of amphibians?

As we have described earlier, amphibians are cold-blooded animals, they cannot regulate their body temperature according to the environment.

Respiratory system

Most amphibians have lungs, gills, and skin for their respiration. Gills are used by young ones to breathe meaning the tadpoles while gills are used by the adult to breathe. Frogs have a larynx to create sound.

Most of the oxygen is absorbed from the skin so for this purpose the skin needs to be wet to absorb the oxygen from the environment. The glands on the skin secret mucus which keeps the skin wet or moist to keep respiration going. The oxygen is directly absorbed into the vessels on the surface of the skin and blood circulates it to the whole body.

Circulatory system

The next system is the circulatory system which is rather complex. Amphibians have three chambers of the heart. They have two atria but a single ventricle, although the single ventricle is divided by a ridge.

The oxygenated blood from the skin and the lungs are received by the right and left atria respectively and then it is pushed into the ventricle where the oxygenated blood is pushed to the body and deoxygenated blood is pushed to the skin and the lungs from where the carbon dioxide is removed from the body.

Reproductive system

The next is the reproductive system of the amphibians. Male amphibians have testicles caudal to the kidneys. Females have ovaries, oviduct and cloaca. The digestive system, urinary, and reproductive systems end at the cloaca, where the waste material with eggs is deposited into the environment.

The life cycle of the amphibians is pretty straight. The females lay eggs in water, which form larvae, having tails also called tadpoles, which mature to become adults having limbs and swim out of the water to live on land. Many males guard the clutch until the larvae or tadpoles hatch out.

There are a few differences in the reproductive cycle of amphibians. Many females undergo parthenogenesis in which the young ones are born without fertilization. Few males carry the clutch of eggs in their mouth until they hatch.

Digestive system

An amphibian has a mouth, esophagus, stomach, and intestine, which ends at the cloaca, where the waste material is removed.

Urinary system

The urinary system consists of kidneys, ureters, urinary bladder, and cloaca from where the waste material is removed.

Nervous system

The nervous system of the amphibians is very complex. Most of the amphibians respond to the external stimuli very quickly. Among all the amphibians on land, frogs have the best hearing and vision.

Musculoskeletal system

They have a well-developed endoskeleton, which is modified to form a tetrapod. The bones are hollow and light, but the limbs are strong. The forelimbs have four digits, while the hind limbs have five digits. Many members, like salamanders, have short limbs, and many are limbless.

Bottom line

In this blog, we covered the general characteristics of amphibians, their anatomy and life cycle, and the important members of the various orders.

Please drop a comment if you like the blog and do let me know what I should cover for you.