THE TAILLESS AMPHIBIANS: FROG – ERAKINA
Frogs are considered as any member of a diverse and largely carnivorous group which consists of short bodied, tailless amphibians composing the order Anura. These species are widely distributed ranging from the tropics to subarctic regions, but to be specific the greatest concentration of species diversity is in tropical rainforest. Frogs hold an account for around 88% of extant amphibian species. The species of frog are one of the five most diverse vertebrate orders. There’s also a Warty Frog species which tend to be called as toads, but the fact is the distinction between frogs and toads is informal; not from the taxonomy or evolutionary history. Humans value frogs as a food resource and also have many cultural roles in literature, symbolism and religion. These species are seen as environmental bellwethers, considering decline in frog populations often viewed as early warning signs of environmental damage. There’s a statistic that shows a significant decline in frog population since the 1950s. 120 types are believed to have become extinct since the 1980s and more than one third of the species are considered to be threatened with extinction.
EVOLUTION OF FROG SPECIES
The origins and evolutionary relationships are hotly debated between the three main groups of amphibians. In 2005, a molecular phylogeny based on rDNA analysis suggested that salamanders and caecilians are more closely related to each other than they are to frogs. Eventually the divergence of the three groups took place in the Paleozoic or early Mesozoic before the breakup of the supercontinent Pangaea and soon after their divergence from the lobe-finned fishes. Some scientific research says that another molecular phylogenetic analysis conducted about the same time concluded that Lissamphibia first appeared about 330 million years ago and that the temnospondyl-origin hypothesis is more credible than other theories. While agreeing with the main thrust of this study, other researchers questioned the choice of calibration points used to synchronize the data. A study was made in 2011 that postulated, Lissamphibia originated no earlier than the late Carboniferous, some 290 to 350 million years ago. There was a split between Anura and Caudata which was estimated as taking place 292 million years ago, but later most molecular studies suggest with the caecilians splitting off 239 million years ago.
True Frogs, also the earliest known species that fall into the anuran lineage proper, all lived in the early Jurassic period. Among this, one such early frog species was discovered in 1995 in the Kayenta Formation of Arizona and dates back to the early Jurassic epoch around 175 million years ago, making Prosalirus somewhat more recent than Triadobatrachus. According to study there’s another early Jurassic frog which is Vieraella Herbsti, known only from dorsal and ventral impressions of a single animal and was estimated to be 33 mm from snout to vent. The genetic studies state that the families Hyloidea, Microhylidae and the clade Natatanura diversified simultaneously some 66 million years ago.
All over the earth’s continent there has been the existence of frog species. It was announced in 2020 that 40 million year old helmeted frog fossils had been discovered by a team of vertebrate paleontologists in Seymour Island on the Antarctic Peninsula, eventually indicating that this region was once home to frogs related to those now living in South American Nothofagus forest.
Just like other amphibians, the life cycle of a frog normally starts in water with an egg that hatches into a limbless larva with gills which are commonly known as tadpoles. Later after certain growth, during which it develops limbs and lungs, the tadpole undergoes metamorphosis in which its appearance and internal organs are rearranged. When we talk about reproduction frogs have two main types, the prolonged breeding and explosive breeding. Most of the frogs return to the bodies of water in which they developed as larvae.
Talking about prolonged breeders, male usually arrive at the breeding site first and remain there for some time whereas females tend to arrive later and depart soon after they have spawned. This shows that male outnumber females at the water’s edge and defend territories from which they expel other males. These breeders tend to call in unison creating a chorus that can be heard from far away. Infact, mate selection and courtship is not as important as speed in reproduction.
However, at the breeding site, the male mounts the female and grips her tightly round the body. In this process, the amplexus takes place in the water, the female releases her eggs and the male covers them with sperm where fertilization takes place externally.
CERTITUDE OF FROGS
- A group of frogs are called an army.
- Frogs drink water through their skin.
- Frog species are found all over the world.
- World’s largest frog species is known as the “GOLIATH FROG”.
- A frog’s eyes and nose are on the very top of their head.
- A frog’s call is unique to its species and some frog calls can be heard up to a mile away.
Frogs are predominantly featured in folklore, fairy tales and popular culture. They have a propensity to be portrayed as benign, ugly and clumsy but with hidden talents. Animals are worshipped by the Moche people of ancient Peru and they often depicted frogs in their art. In Panama they have a strong belief that good fortune would come to anyone who spotted a Panamanian golden frog. In ancient Egypt, frogs are considered as a symbol of fertility, water and renewal.
-by PRITISH PAUL