Amphibians are cold-blooded vertebrates that spend part of their life in water and part of their life on land. They breathe through gills and their temperature fluctuates depending on their environment. They have a distinct physical appearance and develop lungs and legs in their later stages of development.
Life cycle
Amphibians develop from a larva into an adult by following a biphasic life cycle. They lay eggs in water and metamorphose into semi-aquatic and terrestrial juveniles. Many amphibians lay thousands of eggs during their life cycle. A large bullfrog’s clutch may contain as many as 45,000 eggs. The size of the eggs determines how long it takes for them to hatch and develop. The egg hatching time can be anywhere from 20 to 270 days.
In Britain, most changes occur during a period of about 4-5 months. Once the tadpoles have grown, they begin to develop their legs. Frogs and toads also lose their tails. As they continue to grow, their bodies become more like adults. When they reach adulthood, they eat mostly insects and small animals but some frogs also eat birds.
Amphibians undergo one of the most remarkable metamorphoses in biology. This process is triggered by hormones released by the tadpole’s thyroid gland. These hormones help prepare the aquatic organism for life on land. During this time, almost every organ undergoes a transformation. In frogs, for example, the paddle tail is retracted, while the lateral line organ is replaced by a bony skull.
The amphibian life cycle typically includes a larval stage, a metamorphic period, and a long period on land before returning to water to lay eggs. The lifespan of an amphibian varies, but it can reach up to 20 years in captivity. However, the average life span of an amphibian is around ten to forty years.
Physical characteristics
The physical characteristics of amphibians are varied, with some species having a small body size of only a centimetre and others reaching as much as 1.5 metres in length. They have gills and breathe through a mouth that is partly covered in a sticky fluid. Their skin is also quite moist and sticky, and they have two pairs of small limbs. Their limbs are usually webbed and they have five fingers. Some species have poison glands on the skin to protect themselves from enemies.
Amphibians live on land and in water. Their eggs are laid in water, where they develop into larvae. The developing larvae must move about and find food, escape predators, and carry out other life functions. Eventually, they grow into adults with four legs and a trunk. All three groups of amphibians undergo metamorphosis, and some of them bear young live. In fact, there are more species of amphibians than in any other group of vertebrates.
Amphibians differ from most reptiles in that they do not have scales or tails. They also have a backbone that begins as cartilage and changes shape as their organs metamorphose. In addition, they have a double-channeled hearing system.
Diet
Mercury is a potentially harmful substance to amphibians. It disrupts the normal development and growth processes, and can cause premature metamorphosis and increased mortality. It can also cause an overall decline in populations. To understand the impact of mercury, scientists at the University of Georgia conducted a study using realistic exposure levels of mercury in amphibian diets.
Most amphibians are cold-blooded, smooth-skinned reptiles with backbones. They are born as aquatic larvae with gills, and most species metamorphose into four-legged terrestrial adults with lungs. Reptiles, on the other hand, lack an automatic body temperature regulation system and must depend on external sources of heat and moisture to maintain body temperature.
The diet of many amphibians is characterized by the presence of live prey. Most adults feed on invertebrates such as earthworms, bloodworms, tubifex worms, springtails, and fruit flies. Some species also feed on small minnows, goldfish, or newborn mice. Invertebrates are the primary food source for most amphibians, but their diets are not suitable for all species.
Environmental sensitivity
Amphibians are particularly susceptible to contaminants, and several studies have suggested that contamination is one of the leading causes of global amphibian decline. However, sensitivity to chemicals in amphibians may not be directly comparable to that in fish. One recent study examined the environmental sensitivity of Central European amphibians to pesticides.
The causes of amphibian environmental sensitivity are poorly understood. Several factors can cause amphibian health and behaviour, including noise and light pollution. A combination of these factors can have a substantial impact on these species. Environmental degradation can affect amphibian populations across a range of life stages, including development, reproduction, and behaviour.
Sensitivity to pesticides varied among species. European amphibians were less sensitive to Folpan than most others. Environmental sensitivity was assessed using an LC50 ratio test and the difference between the two species was considered significant if the 95% confidence intervals did not include zero.
Environmental sensitivity of amphibians in the aquatic stage of pesticide exposure is important for risk assessment. However, amphibians are not included in the current EU environmental risk assessment of pesticides. Therefore, risk assessment for aquatic amphibians depends on data obtained in other species, such as fish.
Frogs are highly sensitive to changes in water quality. Because their skins are permeable, they are sensitive to micro-climatic conditions and pollutant levels. They are important indicators of environmental changes in ecosystems and can provide valuable information about these changes.
Colors
Amphibians have an amazing array of colors. Many of these creatures have brightly colored skin to warn predators or attract mates. Others have dark colored skin to help them absorb heat. It isn’t clear why amphibians use such a wide range of colors, but they do.
Some species of amphibians have blue skin, though this color is rare. The blue-spotted salamander (Ambystoma lateralis) of North America and the Blue Poison Dart Frog (Dendrobates azureus) of South America have this coloration. Other amphibians that are known to have blue skin include the Bull Frog, Rana catesbeiana, and Green Frog, Rana clamitans. However, the blue coloration in these species is rare and temporary. Green coloration in frogs requires blue wavelengths from the surface to develop its characteristic green color.
The Common King Snake is another species with a distinctive reddish color. While not native to the Plateau, it ranges through the Piedmont and Fall Line. It has evolved to live on land and is best known in the Gunpowder Falls region of southern Maryland. Other species of snakes include the cobra snake, and eastern diamondback rattlesnake.
Colors of Amphibians are based on a number of different physical and chemical mechanisms. Some are purely pigmented, while others are iridescent.
Habitat
Amphibians need a variety of habitats to survive. Some prefer moist soil or wet areas where they can burrow. Others use woody material near wetlands or riparian areas to live. They also use small mammal burrows, boulders, and cracks in rocks as habitats. Reptiles, on the other hand, require habitats that provide shelter and a place to bask in the sun. Urban drainage schemes should aim to create suitable habitat by avoiding features such as gully pot drainage or high kerbs, as these features can trap amphibians.
Recent studies have indicated that the global warming of our climate is threatening amphibian populations. Changes in the climate are affecting amphibians’ ecology, behaviour, and physiology. It is also affecting biodiversity and promoting the development of pathogens and disease. It is also affecting the ability of amphibians to disperse, which can result in population decline.
In addition to climate change, amphibians’ habitats will be affected by changes in temperature. These changes would cause their range to decrease, and the species would cease to exist in certain regions. They would also be more vulnerable to pollutants, and fewer of them would survive in these environments. Despite the threats, amphibians can still be protected by adopting conservation measures.
In the last decades, amphibians have been largely protected in many areas. However, environmental degradation has resulted in severe problems for amphibian populations. Acidification has led to increased levels of sulphate and nitrogen in ponds and small lakes. In parallel, the amount of amphibians in ponds and small lakes has increased.
