them. The cane toad (Bufo marinus) is a very adaptable species native to South and Central America. In the 1930s, it was introduced into Puerto Rico, and later various other islands in the Pacific and Caribbean region, as a biological pest control agent. In 1935, 3000 toads were liberated in the sugar cane fields of Queensland, Australia, in an attempt to control cane beetles such as Dermolepida albohirtum, the larvae of which damage and kill the canes. Initial results in many of these countries were positive, but it later became apparent that the toads upset the ecological balance in their new environments. They bred freely, competed with native frog species, ate bees and other harmless native invertebrates, had few predators in their adopted habitats, and poisoned pets, carnivorous birds, and mammals. In many of these countries, they are now regarded both as pests and invasive species, and scientists are looking for a biological method to control them. Human uses Culinary Frog legs are eaten by humans in many parts of the world. Indonesia is the world's largest exporter of frog meat, exporting more than 5,000 tonnes of frog meat each year, mostly to France, Belgium and Luxembourg. Originally, they were supplied from local wild populations, but overexploitation led to a diminution in the supply. This resulted in the development of frog farming and a global trade in frogs. The main importing countries are France, Belgium, Luxembourg, and the United States, while the chief exporting nations are Indonesia and China. The annual global trade in the American bullfrog (Rana catesbeiana), mostly farmed in China, varies between 1200 and 2400 tonnes. The mountain chicken frog, so-called as it tastes of chicken, is now endangered, in part due to human consumption, and was a major food choice of the Dominicans. Coon, possum, partridges, prairie hen, and frogs were among the fare Mark Twain recorded as part of American cuisine. Scientific research In November, 1970, NASA sent two bullfrogs into space for six days during the Orbiting Frog Otolith mission to test weightlessness. Frogs are used for dissections in high school and university anatomy classes, often first being injected with coloured substances to enhance contrasts among the biological systems. This practice is declining due to animal welfare concerns, and "digital frogs" are now available for virtual dissection. Frogs have served as experimental animals throughout the history of science. Eighteenth-century biologist Luigi Galvani discovered the