Bullfrog
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- For other uses, see Bullfrog (disambiguation)}}}.
The American Bull Frog (Rana catesbeiana) is an aquatic frog, a member of the family Ranidae, or "true frogs", native to much of North America.
Description
Bull frogs are large amphibians and can grow to a body length of 6 inches (15 cm) with a weight of 1.5 lb (750 g). Females are typically larger than males. They are generally varying shades of green or brown, with dark brown, dark green, or black blotching and a yellow or white underside.
A bullfrog uses skin, Buccal Cavity, and lungs for respiration. Cutaneous ("skin") gas exchange is very important in all amphibians. They are aptly named, as their call is an extremely loud, guttural bellow that carries a long distance, giving the impression that the frog is much larger than it actually is.
The skeleton of an adult frog consists of bone, hyaline cartilage, and calcified cartilage. The calcified cartilage can be found throughout the body of the frog, its particularly more noticeable in the epiphyses of the long bones in the limbs and shoulder-gridle, etc. The frog not only has a scalpula, but a suprascalpula which allows for greater range of motion for long jumps. In the frog the radius and ulna have become fused into a single bone, the radio-ulna, and the tibia and fibula have become fused into a single bone, the tibio-fibula.
The vertebrae of the frog comprise ten bones; nine are true vertebrae, and the rod-shaped urostyle that is almost as long as the other nine. The head of the frog is flat but its form depends on the extensive separation of the jaw bones; the orbital cavities and the horizontal direction of their floor also have an effect on the form of the head. The central nervous system of the frog is made up of the spinal cord and the brain, where the spinal cord is a bit smaller than the brain. The peripheral nervous system contains the cranial nerves and spinal nerves.
Distribution
Bull frogs are native to North America. They are found in the United States, Canada and Mexico, east of the Rocky Mountains, but have been introduced to many other localities throughout the world. In Europe and the western U.S. measures are often taken to control its spread because it competes with, and often drives out, native species.
They are found in permanent water sources such as ponds, swamps, and slow moving streams, often in areas with dense vegetation. In the fall, during rains, freshly morphed juveniles can often be found wandering far from their home bodies of water.
Diet
Bull frogs are carnivorous and will consume almost anything that fits into their mouth which they can overpower, including insects, small mammals, fish, birds, turtles, snakes, and even other frogs.
Reproduction
The male reproductive organs are the testes and their duct, and the female have ovaries. In the spring the male calls the female from the water. The female lays up to 25,000 eggs, and these eggs will become tadpoles. Their metamorphosis brings them the organs that are only found in the adult frogs and takes between 12-24 months. There are three major changes that take place during the metamorphosis: 1) Premetamorphisis which is when the embryo genesis and growth and development occur, during this time the thyroid gland is absent. 2) Prometamorphisis is the period in which the concentration of the endogenous thyroid hormone rises 3) Metamorphosis is the period when the tadpole's tail shrinks back into the frog's body. Other organs too undergo changes such as the liver and the intestine and the gills will be gone as well. The adult frog can live up to 15 years.
Human use
While occasionally kept as pets, bullfrogs provide a minor food source, especially in the southern states of America, and in some areas of the Midwestern United States. In a few locations they are commercially cultured in ponds, but the traditional way of hunting them is to paddle or pole silently by canoe or flatboat in streams or swamps at night; when the frog call is heard, fix a strong light on the frog. The frog will not jump into deeper water as long as movement is slow and steady. When close enough, the frog is gigged and brought into the boat. The only parts eaten are the rear legs, which resemble small chicken drumsticks, and they are usually fried for consumption. The Bullfrog is also used as a specimen for dissection in many schools across the world.
External links
- [Herps of Texas: Rana catesbeiana]
- [British Columbia Frog Watch Program: Bull Frog Fact Sheet]
- [Sonoran Desert Conservation Plan, Exotic Species: Bull Frog]
References
- Santos-Barrera, G. et al. (2004). [Rana catesbeiana]. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes a range map and justification for why this species is of least concern
- [Rana catesbeiana (TSN 173441)]. Integrated Taxonomic Information System. Accessed on 6 February 2006.
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