Frogs belong to the tailless, short-bodied amphibians; they are mostly short-bodied and of the carnivorous grouping. They are of the Anura order (the Ancient Greek a-, without + Oura, tail). The ancient fossil known as “proto-frog” was seen in the pre-historic Triassic of Madagascar; however, the dates of their origin suggested by the molecular clock are predicted to exist prior to the Permian, which is 265 million years back. Frogs are spread widely from the tropical regions to the subordinate arctic regions. Despite this, the highest diversity of their species occurs in the tropical rain forests. The recorded species number to around 4,800 and more than 85% of the species are amphibian. Apart from this, they belong to one among the 5 greatest varieties of vertebrate orders.
The body structure of the developed frog is normally distinguished by its stout body, jutting out eyes, tongue with cleavers and tailless adults. Apart from life on dry land and fresh water, the adults belonging to certain species become accustomed to life in trees or underground. The frog has glandular skin, having secretions ranging from toxic to unpleasant taste. The warty variety of frogs are at times known as toads; however, toads and frogs are differentiated on the basis of casual naming conventions, giving importance to the warts, and not based on their historical evolution or taxonomy. Certain toads have closer relations to frogs than to toads. The skin of the frogs differs in their color, varying from properly camouflage dappled brown, green and gray to vibrant patterns of brilliant yellow or red and black, the function being to exhibit their toxicity and to give caution to predators.
The two main modes of reproduction of the frogs are explosive breeding and prolonged breeding. In the latter mode that the majority of the species adopts, at definite periods in the year the adult frogs unite together near a pond, stream or lake for breeding. Several frogs go back to the water bodies where they were developed in the form of larvae. The result of this accounts for the yearly migration, which involves thousands of frogs. In the explosive breeding, fully developed frogs come at the sites where they breed based on some features like the rainfall that happens in dry lands. Such frogs mate and spawn very promptly, with the rapid growth of the larvae, so as to utilize the short lived water bodies before they dry up.
Frogs in particular lay eggs in water. The hatched eggs turn into aquatic larvae, known as tadpoles, they have internal gills and tails. Their scratchy mouth portions are very peculiar, suited for omnivorous, herbivorous or planktivorous diets. It is at the time of completion metamorphism into an adult form that their life cycle is complete. Certain varieties bypass the tadpole stage or lay their eggs on land. The diet of the adult frogs is normally carnivorous, they feed on tiny invertebrates; however, the omnivorous varieties are present and some consume fruits.
In the prolonged breeding process, the males arrive first at the breeding sites, and stay there for a period, but the females have a tendency of arriving at a later time and vacate the place immediately after spawning. The males are more than the females near the water borders and protect the territories by driving out other males. They exhibit their presence by calling, frequently alternating their croaks with other frogs in the vicinity. The croaks of the stronger and larger males possess deeper calls that sustain territories of greater quality. The females choose their partners to a certain extent on the basis of deepness of their voice. In certain varieties satellite males exist, having no territories to call their own, and they do not call. They may intercept females who approach a male that calls or occupy a vacated territory and be a satellite.
At the place where they breed, the male mounts upon the female and holds her tightly embracing her in an embrace called Amplexus that typically occurs in the water, the female lays her eggs and the male envelopes the eggs with its sperm; fertilization takes place externally. In most of the varieties like the Great Plains toad (the Bufo Cognatus), the male holds back the eggs with its hind feet, retaining them in position for a period of 3 minutes. The unique West African genus Nimbaphrynoidesbis exceptional among the frogs that are viviparous. Eleutherodactylus Jasperi and Limnonectes Larvaepartus, belonging to the Tanzanian genus Nectophrynoides are the sole ovoviviparous ones. Here fertilization takes place internally and the females deliver the fully grown juvenile frogs, with the exception of the L. larvaepartus, which deliver tadpoles.
Most of the “frog farms” become marshy places, shallow ponds and swamps possessing abundant habitat and food to satisfy the requirements of wild frogs. The culture of certain frog farms, just consist of making an increase in the shore line places, putting up a fence to drive away predators and sustain the frogs, and preserving tadpoles or eggs of the wild frogs. The frogs are on their own, responsible for growing on their own.
For the generation of frogs for the laboratory use in biological research centers and in the medical field, rigorous frog culture techniques indoors are on the run. But presently, there is no guarantee that this technique in indoor culture is suitable economically for the culture of mass production of frogs as food for human beings.
The “Giant Frog” or the common bull frog, about 8 inches long, is a species in North America (Rana Catesbeiana), that many consider has the best prospects for frog farming. However, a proper ratio must be maintained between the water body and the shoreline, and it may be better to have a jagged, uneven shoreline instead of a round or rectangular one, because of its increased shoreline length, because each bullfrog may need a shoreline of 21 feet for its exclusive territorial requirements. You can increase the shoreline by making several islands in the water body and increasing the number of canals or water inlets so as to be able to grow more frog numbers. Alternatively, if you make your ponds as a series of ditches to increase the shoreline and increase the frog counts.
The depth of the ponds is another criterion that befits mention. In the Southern US, a water depth of about 1 to 2 feet may be sufficient, but Northern USA ponds must have at least 6 to 12 feet depth if the frogs are to hibernate successfully in the mud bottom during the winters. Frogs normally prefer to live and feed in the shallow parts of the ponds.
A proper fencing will keep out predators like fish, turtles, snakes, water birds, foxes and cats. Additionally, using a wire net stretched over the shallow area of the pond where the frogs rest, can save them from avian attacks.
Frog farming is not yet part of the organized sector in the US. Several economic, chemical and biological drawbacks stand in the way of rapid commercialization of frog farming. However, the exhaustive hunting of the animal in their wild habitations is reducing the populations of wild frogs, as a result of which, skilled frog farmers are the need of the hour to restitute the frog population to meet the ever growing demand for frog legs.
There is no difference in the technique used in gathering and for harvesting bullfrogs in the pond-culture and the method of capturing wild frogs. The techniques used are hand capture, nets, fishing using a hook and line and spearing. The hooks are baited with earthworms, live insects or synthetic lures (a red cloth piece or yarn) are left to dangle before the frog. At night time, band capture and spearing are done very effectively; here a bright spot light is used for immobilizing and dazing the frog. It is obvious that new techniques to efficiently harvest frogs on a mass basis is mandatory.
Human beings eat frog legs in almost every place, the world over. A Frog leg dish called French Cuisses de Grenouille is a traditional dish specifically seen in the regions of Dombes (Ain Department). This dish is also usual in places where they speak French, such as Louisiana, in particular, the Cajun parts of Southern Louisiana and also the New Orleans, United States. In Asia, they consume frog legs in Vietnam, China, Indonesia and Thailand. In certain regions of China, they farm pig frogs and edible frogs that are consumed in an enormous quantity in Cantonese cuisine and Chinese Sichuan. Frog-leg soup is sold in Indonesia named as Swikee or Swike. The world’s largest exporters of frog meat are Indonesians. They export over 5,000 tones of frog meat every year; the majority of them are exported to Belgium, France and Luxembourg.
Initially local wild populations supplied them; however, as a result of the decrease in supply due to over exploitation, frog farming was developed, trading them universally. Belgium, France, the United States and Luxembourg were the chief importing centers, whereas, China and Indonesia are the main exporting nations. The yearly world trade in American bullfrog (Rana Catesbeiana), mainly farms in China, which varies from 1200 to 2400 tons.