OTHER COMMON NAMES
English: Common Plantanna, African clawed frog, clawed toad, clawed frog, upland clawed frog; German: Glatter Krallenfrosch; Spanish: Rana de garras africana.
Bufo laevis Daudin, 1802, kind locality not designated. Five subspecies are acknowledged.
Xenopus laevis varies in dimension over the vary of the species; males, nevertheless, at all times are smaller than females inside a given inhabitants. Female frogs vary from 2.2 to 5.Eight in (57 to 147 mm) and males from 1.8 to 3.Eight in (45.6 to 97.5 mm) in snout-vent size. The physique and head are depressed, and the small, spherical eyes are placed on high of the top. The pores and skin is clean. The hind limbs are lengthy and strong. The three internal toes of the big, absolutely webbed ft bear small, black claws. The internal metatarsal tubercle is an elevated ridge. The subocular tentacle is minute, lower than half the diameter of the attention, and there are 23–31 lateral-line bars between the attention and the vent. Although the dorsal coloration varies, it often is darkish—grey to greenish brown—and marked with darker blotches. The venter is pale and should bear irregular spots. The toe webbing often is grey and sometimes is tinged with yellow.
Members of this group occupy primarily savannas of the Republic of South Africa north to Kenya, Uganda, and the Democratic Republic of Congo westward to Cameroon. These frogs should not discovered within the Congo Basin or the warmer lowlands of japanese Africa. Owing to the pet commerce and customary use of Xenopus as a laboratory animal, the frog (most probably X. laevis) has been launched in Europe, the United States, and South America. Introduced populations thrive within the United Kingdom (Isle of Wight, South Wales, and southeast and southwest England), mainland Europe (Germany and the Netherlands), Chile (particular locality unknown), Ascension Island, and the United States (Tucson, Arizona; and Los Angeles, Orange, Riverside, and San Diego counties in California).
An extraordinary trait of this species is its obvious environmental tolerances and lack of discrimination with regard to its habitat, so long as there’s a physique of water for the frog to occupy. Doubtless this accounts for the success of the species within the laboratory and as invasive populations all over the world. The species happens in any sort of physique of water, together with rivers, lakes, reservoirs, swamps, flooded pits, ditches, and wells, and at elevations from sea stage to about 9,000 ft (2,780 m) within the Drakensberg Mountains of South Africa. Water high quality seemingly isn’t a difficulty. The species is widespread in stagnant, nonetheless waters and sluggish streams in addition to fast-flowing waters. Similarly, it may be present in water occluded with natural detritus or clear water and in acidic or alkaline waters. Unlike practically all different anurans, the widespread plantanna can tolerate saline waters and has been identified to survive in 25% seawater indefinitely and in 40% seawater for just a few days. Temperature, because it impacts larvae, could also be a limiting issue for the species, though they show a exceptional tolerance; in laboratory exams, the important deadly minimal and most temperatures for larvae have been proven to be 50°F (10°C) and 95°F (35°C), respectively. Introduced populations survive in ice-covered ponds for a number of months a year in addition to in ponds which are topic to the intense summer time temperatures of southern Arizona. In the launched southern California populations, when temperatures attain 86°F (30°C), the frogs burrow into the pond backside to depths of about 12–16 in (30–40 cm), the place the temperature is comparatively secure at 68°F (20°C).
Under good circumstances, members of this group don’t depart the water, though they could undertake quick nocturnal excursions. Prolonged drought, nevertheless, forces them to estivate. They have been noticed to estivate within the laboratory for up to eight months and likely are able to the identical in nature, the place they burrow backward into drying mud and occupy a vertically oriented chamber. Physiological exams reveal that estivating X. laevis have quite a lot of variations to survive desiccation and hunger. Rather than excreting ammonia, which is very poisonous, they excrete the less-toxic urea that’s gathered within the blood, liver, and muscle tissue. The frogs can cut back their oxygen consumption by 30%. Frogs maintained in water can survive a year with out food and incur as a lot as a 35–45% loss in physique weight. They survive through the use of saved carbohydrates and lipids for power for the primary 4 to six months, after which era, the frogs change to protein catabolism (particularly breakdown of physique muscle) for power. If they survive an prolonged interval of drought, they’re seemingly to migrate over land en masse with the onset of torrential rains.
FEEDING ECOLOGY AND DIET
The food preferences of this species are as vast ranging as are the aquatic habitats wherein the species is discovered. Typically, the hatching of tadpoles coincides with algal blooms, and the larvae, which have a extremely specialised filter-feeding mechanism, are ready to extract algae and the best suspended natural matter from the water. Recently metamorphosed froglets appear to focus on small crustaceans and aquatic insect larvae. Adults eat bugs and prey on or scavenge different vertebrates— anurans, fish, birds, and small mammals. They have been seen to leap out of the water to seize winged bugs. Although the species usually isn’t present in our bodies of water with excessive pure populations of fishes, it’s identified to prey sometimes on fish in constrained conditions (e.g., remoted swimming pools and hatcheries). Adult frogs feed on different species of anurans and are cannibalistic with respect to their very own larvae and younger. They will eat small birds and rodents that fall into the water. There isn’t any proof that the species feeds on land, and on this regard they’re fairly distinct from most different anurans.
Under laboratory circumstances, the widespread plantanna will breed all year long and attains ####ual maturity in eight months (i.e., six months after metamorphosis). In nature, when these frogs are uncovered to seasonal variations in temperature (e.g., South Africa), growth most likely is slower. Mating coincides with the onset of heavy rainfall and a temperature of about 68°F (20°C) and thus varies all through the vary of the species. Oogenesis is decided by food provide, and prey abundance correlates positively with rainfall; thus, the onset of rainfall not directly stimulates egg manufacturing. Heavy rains wash recent sediments into the breeding websites and enrich the vitamins; this, in flip, triggers phytoplankton blooms that present food for growing larvae.
Both female and male frogs name, and the calls fluctuate in size, sample, and frequency all through the vary of the species. In South African widespread plantanna, the male commercial name is described as a protracted trill composed of alternating fast-pulsed (43–66 pulses per second) and slow-pulsed (24–42 pulses per second) parts, with the quick aspect lasting 0.18–0.6 seconds and the gradual aspect lasting 0.34–0.9 seconds. Calling continues for a number of minutes, and frequencies up to 2.Three kHz are emphasised. When males clasp females in inguinal amplexus, they utter a tender amplectant name. Typically about 1,000 eggs are laid at a time and hooked up to aquatic vegetation or different underwater objects. The pale brown eggs are about 0.05 in (1.15 mm) in diameter.
SIGNIFICANCE TO HUMANS
X. laevis might be one of the crucial acquainted frogs to people, owing to its lengthy use as a mannequin system for biomedical analysis and its reputation within the pet commerce. Until the 1940s these frogs have been used for being pregnant exams; injection of a small quantity of urine from a pregnant lady beneath the frog’s pores and skin causes the frog to lay eggs. Biomedical researchers found that the species is a handy experimental organism. It is straightforward to keep in aquariums, and it’s strong and has a comparatively quick life cycle. Unlike most different amphibians, it may be induced to present fertile embryos all year long, and the embryos and their cells are massive, making them handy topics for experimental manipulation and molecular analysis. In the previous, members of this species have been used as a food supply in Cameroon, Sierra Leone, Central African Republic, Uganda, Rwanda, and the Democratic Republic of the Congo. The indigenous people of these international locations used baited wicker baskets or traps to seize the frogs or sometimes drained smaller our bodies of water and picked up the stranded frogs.