African clawed frog
The African clawed frog (Xenopus laevis, also known as platanna) is a species of South African aquatic frog of the genus Xenopus. It can grow up to a length of 5 in (12 cm) with a flattened head and body, but no external ear or tongue. Its name is derived from the three short claws on each of its hind feet, which it probably uses to stir up mud to hide itself from predators.
The species is found throughout most of Africa, and in isolated, introduced populations in North America, South America, and Europe.
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 more commonly sold as pets. The ACF pictured can also be found available for sale but is quite often incorrectly labeled as a Congo Frog or African dwarf frog because of similar colourings. They reproduce by laying eggs (see frog reproduction).
The average life-span of these frogs ranges from 5 to 15 years with some individuals having been recorded to live for nearly 20 years. They shed their skin every season, and eat their own shed skin.
Although lacking a vocal sac, the males make a mating call of alternating long and short trills, by contracting the intrinsic laryngeal muscles. Most unusually, females also answer vocally, signaling either acceptance (a rapping sound) or rejection (slow ticking) of the male.
Use in research
Although X. laevis does not have the short generation time and genetic simplicity generally desired in genetic model organisms, it is an important model organism in developmental biology. X. laevis takes 1 to 2 years to reach sexual maturity and, like most of its genus, it is tetraploid. However, it does have a large and easily manipulable embryo. The ease of manipulation in amphibian embryos has given them an important place in historical and modern developmental biology. A related species, Xenopus tropicalis, is now being promoted as a more viable model for genetics. Roger Wolcott Sperry used X. laevis for his famous experiments describing the development of the visual system. These experiments led to the formulation of the Chemoaffinity hypothesis.
Xenopus oocytes provide an important expression system for molecular biology. By injecting DNA or mRNA into the oocyte or developing embryo, scientists can study the protein products in a controlled system. This allows rapid functional expression of manipulated DNAs (or mRNA). This is particularly useful in electrophysiology, where the ease of recording from the oocyte makes expression of membrane channels attractive. One challenge of oocyte work is eliminating native proteins that might confound results, such as membrane channels native to the oocyte. Translation of proteins can be blocked or splicing of pre-mRNA can be modified by injection of Morpholino antisense oligos into the oocyte (for distribution throughout the embryo) or early embryo (for distribution only into daughter cells of the injected cell).
Extracts from the eggs of X. laevis frogs are also commonly used for biochemical studies of DNA replication and repair, as these extracts fully support DNA replication and other related processes in a cell-free environment which allows easier manipulation.
X. laevis is also notable for its use as the first well-documented method of pregnancy testing when it was discovered that the urine from pregnant women induced X. laevis oocyte production. Human chorionic gonadotropin (HCG) is a hormone found in substantial quantities in the urine of pregnant women. Today, commercially available HCG is injected into Xenopus males and females to induce mating behavior and breed these frogs in captivity at any time of the year.
As a pest
When African clawed frogs are imported into non-native countries, they have the capacity to wreck entire ecosystems by eating native wildlife such as fish and turtles that have no natural defense against these creatures.
In 2003, these frogs were discovered in a pond at San Francisco's Golden Gate Park, where much debate exists on how to terminate these creatures and keep them from spreading. It is unknown if these frogs entered the San Francisco ecosystem through intentional release or escape into the wild.
Because these frogs are immune to the fungi Batrachochytrium dendrobatidis (a chytridomycota) and B. dendrobatidis has been traced back to the habitat of Xenopus laevis in Africa, many scholars believe it is the source of the worldwide frog population crash. Due to its extensive use in obstetrics and research, it appears Xenopus laevis has carried B. dendrobatidis with it out of Africa to all over the world, causing chytridomycosis and eventually death in native frogs naïve to the fungi.
As a pet
Your Frogs Home
ACF's are nomally sold when they are about the size of a 2p, but will grow rapidly. A tank of about 90L is ideal for one but a larger tank will be needed if you want to house more. This should give adequate swimming space depending on the size they grow to. The tank should be kept the same as a cold water tank for goldfish, with an internal filter and lighting. You need to use dechlorinator and allow the tank to mature. The tempreture should be between 18c and 24c. Even though they are often kept warmer than this in pet shops.(Your local pet shop can advise you of this). The base of the tank should be covered with gravel, sand or a mixture of both but nothing sharp that can harm their soft underbodies. You can decorate the tank with aquarium ornimants but check for sharp edges and any caves they may get stuck in. A cave should be supplied in the tank so they have somewhere to hide, but check the size for a full grown adult ACF to get in and turn around easily. Plants are good for your ACF to hide behind as well as a nice area for them to hold on to when they float. A tubliflex feeder can be added to the tank, this is a small cup with holes that sticks to the side of the tank and allows the live food to leave slowly giving all your frogs a chance to eat.
Check with the pet shop if your baby ACF can get into your filter!
Ask someone who has a good, clean, well established cold water / tropical tank to give you some water and bacteria to start your tank quicker (their help in maintaining the tank could become valuable!)
Feeding Your Frog
There is much confusion on what an ACF will and wont eat. The tried and tested method of raising and keeping happy ACF's is simply blood worm. The cheaper and safer method is frozen blood worm. This can be left to melt in or out of the tank. You can then pour it into a feeder or hand feed your frog. Your frog will hunt the floor cleaning leftovers. Live blood worm is also good but make sure you trust the supply. Other readerly available frozen and live foods like Daphnia, brine shrimp and shrimp can also be used but will need to be incresed to supply a good source of food for all your frogs. Other foods can be tried but be prepared to take it out of your tank if your frogs refuse to eat it. I feed the babies 1/2 a block every other day and the adults 2 - 3 blocks every other day.
If you want to hand feed your frog create a routine they will get used to then they will exspect to be fed.
My routine - light on, lid up, lightly wriggle your fingers to get their interest and then hold food on the surface until they collect it. Try not to move or jerk your hand this will scare them and it will take longer for them to trust you.
Although a lot of people would not recomend raising any other animals in the same tank, I did raise two of mine with a king plec (larger than them) and a few fancy goldfish (also large). This was a good set up until the goldfish got too large, then they had to be moved to make space for the frogs. This set up only worked because I started with baby ACF's and hand fed them, so they did not have to compete for food. My tank was 190L and the goldfish still had to be moved be prepared for this! If you are going to keep anything in the tank with your frogs make sure it will grow at the same rate (Fancy goldfish are good for this, buy large) large plec and cat's also work but make sure your frogs don't get bullied. Dont buy anything flat, too fast swimming or hectic.
A company that sells them is Grow-a-Frog.
- ^ Tinsley et al. (2004). Xenopus laevis. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006. Database entry includes a range map and justification for why this species is of least concern
- ^ ADW: Xenopus Laevis: Information
- ^ Comparison of morpholino based translational inhib...[Genesis. 2001] - PubMed Result
- ^ Blow JJ, Laskey RA (1986 month = November). "Initiation of DNA replication in nuclei and purified DNA by a cell-free extract of Xenopus eggs..". Cell 47 (4): 577-87. PMID 3779837.
- ^ "Killer Meat-Eating Frogs Terrorize San Francisco". FoxNews. http://www.foxnews.com/story/0,2933,258519,00.html.
- ^ "The Killer Frogs of Lily Pond:San Francisco poised to checkmate amphibious African predators of Golden Gate Park". San Francisco Chronicle. http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/03/12/BAGLUOJLDE1.dlkhgidofyugDTL.