What is an Amphibian?
Amphibians are cold blooded vertebrates that belong to the class Amphibia and need water, or damp habitats, to survive, there are around 8,450 known species of Amphibians. But the question 'what is an Amphibian' can be a lot more complex. We've taken a deep dive into this question for you.
They are characterised by a unique life cycle that typically involves an aquatic larval stage and a terrestrial adult stage.
Amphibians include three main groups and encompass an incredible diversity of creatures, from the acrobatic leaps of frogs to the sleek, secretive movements of salamanders and the subterranean mysteries of caecilians.
Amphibian characteristics
Amphibians, with their existence in water and on land, exhibit a set of unique characteristics that set them apart in the animal kingdom. From their metamorphosis to their intricate adaptations for survival, they have some really interesting characteristics!
Metamorphosis:
At the heart of their charm is that they undergo metamorphosis, a transformation from aquatic larvae to adult amphibians. In simple terms, it's a remarkable and sometimes visually striking transition from one life stage to another, for the amphibian species, this is from larvae that live in the water to adults who live on the land.
Permeable Skin:
The permeable and thin skin of amphibians takes center stage, serving as an armor to their surroundings. It is also a crucial organ for respiration.This remarkable feature renders them exceptionally responsive to environmental changes.
Dual Respiration Methods:
The Amphibian respiratory is a dual methods - utilising both lungs and skin. This intricate dance enables them to thrive in diverse habitats. Moist environments play a pivotal role, highlighting the delicate balance required for respiratory efficiency.
The Amphibian life cycle consists of several distinct stages, each marked by unique physiological and morphological changes. Let's explore the typical life cycle of amphibians:
Life cycle of amphibians
Egg Stage:
The life cycle begins when amphibians lay eggs. Eggs are usually laid in water, and the method of egg deposition varies among most amphibians species.
Embryonic Stage:
The eggs hatch into aquatic larvae, commonly known as tadpoles in the case of frogs and toads. These newly hatched larvae are adapted to an aquatic lifestyle and have external gills for breathing underwater.
Larval Stage:
Tadpoles undergo a period of growth and development in this stage. They feed on algae and small water organisms. During this phase, they have tails and lack limbs.
Metamorphic Stage:
Undergoing metamorphosis is a pivotal stage where the tadpole undergoes significant changes to transform into an adult form. Limbs develop, the tail is absorbed, and they develop lungs for breathing air.
Juvenile Stage:
After metamorphosis, young amphibians emerge from the water onto land. At this point, they resemble miniature versions of the adult form but may not yet have reached full maturity.
Adult Amphibians:
The final stage of the life cycle is the fully mature adult amphibian. Adults are adapted for a terrestrial lifestyle but may still require access to water for breeding.
Amphibian habitats
Amphibians are a diverse group of animals that occupy a range of habitats, showcasing their adaptability to various environmental conditions and all Amphibians spend time both on land and in water.
Many Amphibians, especially during their reproductive stages, are closely associated with freshwater habitats such as ponds, lakes, streams, and marshes. These environments provide suitable conditions for egg-laying and offer a nurturing space for amphibian larvae.
Once they undergo metamorphosis and transition into adults, amphibians live in terrestrial environments. Forests, grasslands, and meadows become their home, offering ample hiding places, foraging opportunities, and potential breeding sites.
Tropical rain forests, such as in central and South America, are rich in the Amphibian animal group. The dense vegetation and high humidity create favourable conditions for many amphibians, including a variety of frog species and salamanders.
Amphibians can also be found in human altered landscapes. Ponds in parks, gardens, and even backyard habitats can serve as breeding sites for various Amphibian species.
Major Amphibian Groups
Amphibians are classified into three major groups based on their characteristics and evolutionary relationships.
Each group represents a unique branch in the amphibian family tree, showcasing distinct features and adaptations. Here are the three major Amphibian groups:
Anura (Frogs and Toads):
Anura is the largest and most diverse group, encompassing over 7,000 species. These amphibians are known for their distinctive hind limbs adapted for jumping and leaping. Unlike other species, they lack tails in their adult forms. Frogs are one of the only Amphibians native to the UK, along with toads and newts.
Caudata (Aquatic Salamanders and Newts):
Caudates typically have slender bodies, long tails, and smooth, moist skin. Unlike frogs and toads, they retain their tails throughout their lives. Nearly all amphibians species have the ability to regenerate lost body parts.
Gymnophiona (Caecilians):
Caecilians are limbless and often resemble large earthworms or snakes. Their eyes are typically small or even hidden, and they have specialised adaptations for burrowing.
A few Species of Amphibians
>Chinese Giant Salamander holds the title of being the largest amphibian in the world, with some of the Chinese Giant Salamander species reaching lengths of over 1.8 meters.
<American Bullfrog is one of the largest frogs in North America, the American Bullfrog is recognized by its greenish-brown color
< African clawed frogs is a type of frog species that has short black claws on its feet.
< Paedophryne amauensis is the worlds smallest Amphibian and it is, on average, 7 mm big.
Are Amphibians reptiles?
No, Amphibians are not reptiles. Amphibians and reptiles belong to separate classes within the animal kingdom. Amphibians are a class of cold blooded vertebrates that typically have moist skin, lay eggs in water, and undergo metamorphosis from water larvae to land animals. Examples of Amphibians include frogs, toads, salamanders, and newts.
Reptiles, on the other hand, are a separate class of cold-blooded vertebrates characterised by having dry, scaly skin and laying eggs on land. They do not undergo metamorphosis as amphibians do. Examples of reptiles include snakes, lizards, turtles, crocodiles, and alligators.
Do Amphibians lay eggs?
Yes, Amphibians typically lay eggs. Many Amphibian species, such as frogs and toads, lay their eggs in water. These eggs are often laid in clusters or gelatinous masses and are usually attached to vegetation or submerged objects. The eggs hatch into aquatic larvae, such as tadpoles, which undergo metamorphosis into adults.
Some Amphibian species, particularly certain types of salamanders and caecilians, lay their eggs in terrestrial environments. These eggs may be buried underground or deposited in moist areas such as leaf litter or under rocks. The embryos develop directly into miniature versions of the adults, bypassing a larval stage.
How do Amphibians breathe?
All Amphibians use a range of breathing techniques to survive in all of the diverse habitats you will find them in, they will also use different methods depending on which stage of their life they are in.
Through their thin and permeable skin, amphibians can exchange gases directly with the surrounding environment, absorbing oxygen and releasing carbon dioxide. This is called Cutaneous respiration and it plays a vital role in an Amphibians life, especially in smaller species and during periods of low oxygen availability in aquatic environments.
Adult Amphibians will use pulmonary respiration through their lungs, this is perfect for providing an alternate means of oxygen intake when on land. Amphibians will open and close their mouths to force air into their lungs so that they can breathe air.
As larvae, a lot of amphibians rely on gill respiration. Through these external gills they will do a gas exchange with the surrounding water. As tadpoles metamorphose into adults, the gills are often replaced by lungs, though some species retain gills their entire lives, particularly those inhabiting permanently aquatic environments. These varied respiratory adaptations equip Amphibians to thrive in both aquatic and terrestrial environments throughout their life cycle.
What do Amphibians eat?
Amphibians have diverse diets depending on their species and life stage. Many amphibians are carnivorous, feeding on a variety of prey such as insects, worms, spiders, small fish, and even other amphibians.
Some amphibian species, particularly tadpoles and certain adult amphibians like certain species of frogs and salamanders, feed primarily on algae, plants, and detritus. There are also amphibian species that have omnivorous diets, consuming both plant matter and animal prey. This includes species that may feed on fruits, vegetation, and insects or other small animals.
Sometimes, Amphibians swallow their prey whole, aided by their sticky tongues and relatively large mouths. Many species lack teeth or have simple teeth, so they rely on swallowing prey whole rather than chewing. This method of feeding helps them efficiently consume their food and digest it later through their digestive system.
