340mya Amphibians

FROGS, SALAMANDERS & CAECILIANS.

Amphibians are a class of cold-blooded vertebrates that don't have scales made up of frogs, toads, salamanders, newts, and caecilians (wormlike animals with poorly developed eyes).  All amphibians spend part of their lives in water and part on land, which is how they earned their name—“amphibian” comes from a Greek word meaning “double life.” These animals are born with gills, and while some outgrow them as they transform into adults, others retain them for their entire lives.

Amphibians are the ancestor of all land vertebrates with four feet, the tetrapod. Amphibians include frogs, toads, salamanders, newts and caecilians. While amniotes either give live births or lay waterproof eggs, the amphibians retain the ancestral practice of laying eggs in water. Unlike the waterproof skin of amniotes, the amphibian skin allows body water to evaporate through it, restricting amphibians to land areas with access to fresh water.

Many undergo metamorphosis, a biological process which turns juveniles or larvae into drastically dissimilar adult forms for reproduction, and about pedomorphosis, another process which enables juveniles of some species to become sexually-mature without ever developing into their usual adult forms. Species which undergo metamorphosis include butterflies, barnacles and salamanders. Species which exhibit neoteny, a type of pedomorphosis, include human, ostrich, pekingese and axolotl. 

This inconspicuous group is at ground zero of the Anthropocene mass extinction. With extinction rates over two hundred times the global average and potential threatened species loss of over twenty five thousand times that average, coinciding with a general lack of stewardship needed to fully understand the root causes of their extinction, the amphibians will likely be the major casualty of climate and other anthropogenic activities. However, the story doesn’t stop there. And their loss may also have a direct impact on a lot of other species. Amphibians are an important part of the diet of a number of species of reptiles, birds, and mammals, as well as the main predator for a number of groups of insects, thus their extinction will have profound impacts on a broad part of the food chain. That is why many ecologists believe that the amphibians are the “canary in the coal mine” for the impact of human activities on global diversity.