牛蛙Lithobates catesbeianus
形态特征：雄性体长111～178mm，雌性120～183mm。体型大，体重可超过1kg但个体大小与年龄有关。背部、体侧散生小疣，但不太明显；无背侧褶；颞褶清晰；第五趾外侧有缘膜。雄性有内声囊；鼓膜大，几乎相当于眼径的2倍。背面呈墨绿色或黑绿，散缀深色小斑点，背上及体侧的小疣正位置斑点之中。腹面苍白色，散有边缘不太清晰的云雾状花纹；四肢腹面斑纹较多。
生活习性：牛蛙原分布于美洲，20世纪60年代引入我国人工饲养，现已广泛流散我国各地，自生自繁于湖泊、池塘、水库、稻田等静水域内，从沿海低地到云贵高原大约1700m海拔垂直带。鸣声宏亮音似牛嚎，5—7月为产卵高峰，产卵量与年龄和个体大小有关，4000～20000粒不等。卵大1.5mm，动物极黑褐色，植物极白色。充分发育的蝌蚪全长可达120mm以上，早期卵孵出的当年可完全变态，但大部分个体越冬后翌年完全变态。
地理分布：原产于北美，后被引入世界多地。
环渤海地区分布：均有发现，除辽宁外均已发现自然繁殖种群。
注：该种为著名的食用蛙类，个体较大且适应能力强，现已入侵国内诸多水系，对本土物种危害极大，不仅捕食本土物种，还竞争食物及生存空间，应严禁将其放生于开放水域，并防止养殖逃逸现象发生。
Anura Ranidae Lithobates
69.Lithbotes catesbeianus
Description Adults' size normally reaches 111-178mm SVL in males, 120-183mm SVL in females, and large, mature individuals can reach 1,000g (weight varies with size and age); small warts on the dorsum and the body sides; dorsolateral folds of skin absent;temple folds of skin is clear; velums on the outside of the 5th toe; males have gular sacales and tympanums; the tympanums of males are about 2 times bigger than their eyes, easily be seen just behind the eyes and the end close to them.The dorsum color is olive green or dark green, with black spots and small warts; blurred cloud-shaped pattern on the edge of the whitish belly; limbs have lots of markings.
Behaviour Lithbotes catesbeianus are native to America.They are introduced into China in 1960s and its range now extends all over China, from the coastal continental shelf to the Yungui Plateau with 1,700m elevation vertical zone.They grow and breed in deep waters, such as lakes, ponds, reservoirs and paddy fields.They call loudly, just like a bull's howl.The female normally deposits eggs from May to July.The amount of their eggs varies with individual's size and age, from 4,000 to 20,000.The size of the egg is about 1.5mm,with black brown animal pole and white plant pole.Fully developed tadpoles may grow to 120mm in length.Newly hatched tadpoles may be holometabolous in the same year, but the most tadpoles may be holometablous in the spring next year.
Distribution Native to North America and then are introduced to the world.Distribution around Bohai Sea: found but not form the natural breeding population in Liaoning Province.
Notes Lithbotes catesbeianus provide a famous food source.The frogs are large, have powerful leaps, and inevitably escape after which they may wreak havoc among the native frog population.Releasing them in open waters should be forbidden and prevent them escape during feeding.
