Xenopus laevis


Xenopus laevis
Albino African Claw Frog
金蛙
The African clawed frog (Xenopus laevis, also known as the platanna) is a species of South African aquatic frog of the genus Xenopus. Its name is derived from the three short claws on each hind foot, which it uses to tear apart its food. The word Xenopus means "strange foot" and laevis means "smooth".
African clawed frogs can grow up to a length of 5 in (12 cm). They have a flattened head and body, but no tongue or external ears.
The species is found throughout most of Africa, and in isolated, introduced populations in North America, South America, and Europe. All species of the Pipidae family are tongueless, toothless and completely aquatic. They use their hands to shove food in their mouths and down their throats and a hyobranchial pump to draw or suck food in their mouth. Pipidae have powerful legs for swimming and lunging after food. They also use the claws on their feet to tear pieces of large food. They lack true ears but have lateral lines running down the length of the body and underside, which is how they can sense movements and vibrations in the water. They use their sensitive fingers, sense of smell, and lateral line system to find food. Pipidae are scavengers and will eat almost anything living, dying or dead and any type of organic waste.

These frogs are plentiful in ponds and rivers within the south-eastern portion of Sub-Saharan Africa. They are aquatic and are often greenish-grey in color. Albino varieties are commonly sold as pets. “Wild-type” African Clawed Frogs are also frequently sold as pets, and often incorrectly labeled as a Congo Frog or African Dwarf Frog because of similar colorings. They are easily distinguished from African Dwarf Frogs because African Clawed Frogs have webbing only on their hind feet while African Dwarf Frogs have webbing on all four feet. They reproduce by laying eggs (see frog reproduction). Also, the clawed frogs are the only amphibians to have actual (though small) claws.
The average life-span of these frogs ranges from 5 to 15 years with some individuals recorded to have lived for 20–25 years. They shed their skin every season, and eat their own shedded skin.
Although lacking a vocal sac, the males make a mating call of alternating long and short trills, by contracting the intrinsic laryngeal muscles. Females also answer vocally, signaling either acceptance (a rapping sound) or rejection (slow ticking) of the male. This frog has smooth slippery skin which is multicolored on its back with blotches of olive gray or brown. The underside is creamy white with a yellow tinge.
Male and female frogs can be easily distinguished through the following differences. Male frogs are usually about 20% smaller than females, with slim bodies and legs. Males make mating calls to attract females, sounding very much like a cricket calling underwater. Females are larger than the males, appearing far more plump with hip-like bulges above their rear legs (where their eggs are internally located). While they do not sing or call out like males do, they do answer back (an extremely rare phenomenon in the animal world)


Both males and females have a cloaca, which is a chamber through which digestive and urinary wastes pass and through which the reproductive systems also empty. The cloaca empties by way of the vent which in reptiles and amphibians is a single opening for all three systems

In the wild, Xenopus laevis are native to wetlands, ponds and lakes across arid/semiarid regions of southern Africa. Xenopus laevis and Xenopus muelleri occur along the western boundary of the Great African Rift. The people of the sub-Saharan are generally very familiar with this frog, and some cultures use it as a source of protein, an aphrodisiac, or as fertility medicine. Wild Xenopus are much larger than their captive bred counterparts

 

金蛙是一种用途广、容易人工饲养的实验动物。其主要特点是幼体和变态后的成体都营水生生活。虽然它有强壮且肌肉发达的后腿,但由于趾间有全蹼,并且四肢对躯体支撑能力有限,所以只善于游泳而不善于陆地跳跃生活,它幼体全透明,可清楚看见内部结构,成体粉红色,非常可爱。此外,由于爪蟾自身的形态特点,使其在科研领城中用途极广,同时是水族箱中重要的宠物,其市场价格也相当可观。现在越来越多的人把爪蟾称作“金蛙”,深受饲养者的欢迎。
  成体雌性长约12.5厘米,而雄性体长只有雌性的一半。体肥壮,流线型。眼小,位于头背上方,无眼硷。无舌,咽鼓管孔单个。后肢粗壮,趾蹼极发达,内侧3趾末端有爪,故而得名爪蟾。
  以小鱼、虾、蟹、昆虫为食;特别能消灭蚊子的卵和孑孓。终生水栖。遇干旱时,可爬行短距离寻找水源,但一般优于湿冷土下。早春或夏末产卵,一年产卵多达1-1.5万粒,卵通常粘附于水草上。蝌蚪头扁,无角质颌和角质齿,摄食浮游生物。
  常被用作实验动物,很早用于诊断妇女早期妊娠。

1 养殖条件
  以大中型的玻瑞水族箱或圆形玻璃缸进行室内饲养,放入井水或曝气一夜以上的自来水,水深20厘米,水温12~25℃,在水中放入一些卵石和大石块搭成洞穴,箱顶有3个20瓦日光灯加光,水中有潜水泵加氧,加热器给予加热。本实验是在5月开始饲养,11月中旬开始加温而获得受精卵完成繁殖的。具有适宜北方操作的实际意义。
  2 饲养
  成体爪蟾每周喂2一3次水丝蚓或猪肝片,一般不需要给维生素。爪蟾能主动寻找食物,利用前肢将食物拨进嘴里。爪蟾怕惊扰,一般在夜间取食。它非常贪吃,取食量与月增重量成正比,日增重量曲线随投食量增减而变化。水槽里的水应该定期更换,一般在每次喂食后换水,以保证爪蟾的健康,防止疾病的发生。在人工条件下只要管理适当,死亡率较低,每年仅2%左右,幼体的成活率则为75%左右。
  3 繁殖
  性成熟的爪蟾雌雄差别明显。产卵前雌性泄殖腔唇明显地突出变成红色,而雄性前臂内侧有黑色粗条纹的“婚垫”产生。爪蟾性成熟后即会出现抱对现象,抱对时间约为4~6小时,随后在适宜的温度(20一25℃)的条件下可以实现多次少产卵。1只雌性爪蟾一般怀卵为1600枚左右,1次产出量为100一300枚。卵为乳白色的,外有较厚卵胶膜,卵常粘着在缸壁、缸底及水草上,此时应捞出所有成体爪蟾,防止弄破或吃掉卵或胚胎,影响成活率。受精卵发育至蝌蚪大约需一周左右,4天左右卵胶膜开始被吸收,7天蝌蚪已开始游泳。蝌蚪全身透明,头部较大、头背:侧可见脑的组成及部分脑神经的走向,头部腹面观接近五边形,口部有两条口须,尾部较尖长,腹面:两侧各有一个斜向出水孔。蝌蚪是滤食性的,可以投喂细的幼鱼饵料等悬液,混浊度应以蝌蚪在4一5小时内能吃净为宜。蝌蚪有时也吃水中轮虫和刮食绿藻。在20℃条件下,从受精卵经过5一6周就可完:成变态。变态时,蝌蚪进食量减少或停止进食,变态后小爪蟾就可进食水丝蚓或小片猪肝。在室内养殖条件下1一2年内可达到性成熟。
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