Northern Leopard Frog

The Northern Leopard Frog(Lithobates pipiens^[1][2], previously Rana pipiens) is a species of Leopard frog from the true frog family native to parts of Canada and United States. It is the State Amphibian of Minnesota and Vermont.

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Physical description

  The Northern Leopard Frog is a fairly large species of frog reaching about 11 centimeters (4.3 in) in length. It varies from green to brown in dorsal colour with large dark circular spots on their back, sides and legs. Each spot is normally bordered by a lighter ring. A pair of dorsolateral folds starting from the back of the eye run parallel to each other down the back. These dorsolateral folds are often lighter or occasionally pinkish in colour. There is also a pale stripe running from the nostril, under the eye and tympanum, terminating at the shoulder. The ventral surface is white or pale green. The iris is golden and toes are webbed.

Ecology and behaviour

Northern Leopard Frogs have a wide range of habitats. They are found in permanent ponds, swamps, marshes and slow moving streams throughout forest, open and urban areas. They normally inhabit water bodies with abundant aquatic vegetation. They are well adapted to cold and can be found above 3,000 meters (9,800 ft) asl. Males make a short snore-like call from water during spring and summer. Up to 6,500 eggs are laid in water, and tadpoles complete development within the breeding pond. Tadpoles are light brown with black spots, and development takes 70-110 days, depending on conditions. Metamorph frogs are 2-3 centimeters (0.75-1.25 in) and resemble the adult.

This species was once quite common through parts of western Canada until declines started occurring during the 1970s. The decline is thought to have been caused by pollution drift from the United States falling in the form of acid rain. Many populations of Northern Leopard Frogs have not yet recovered from these declines.

Northern Leopard Frogs are preyed upon by many different animals such as snakes, raccoons, other frogs and even humans. They do not produce distasteful skin secretions and rely on speed to evade predetation.

This species is similar to the Pickerel frog (Lithobates palustris' aka 'Rana palustris) and the Southern Leopard Frog (Lithobates sphenocephalus' aka 'Rana utricularis).

Medical research

The Northern Leopard Frog produces specific ribonucleases in its oocytes. Those enzymes are potential drugs for cancer. One such molecule called ranpirnase (onconase) is in clinical trials as a treatment for mesothelioma and lung tumours. Another called amphinase was recently described as a potential treatment for brain tumors ^[3].

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