biology

Western clawed frog

Western clawed frog is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Western clawed frog rather than just read about it. In short: The western clawed frog (Xenopus tropicalis) is a species of frog in the family Pipidae, also known as tropical clawed frog. It is the only species in the genus Xenopus to have a diploid genome.

Key takeaways

Western clawed frog belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Western clawed frog to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Western clawed frog from memory before moving on to harder problems.

Reference excerpt

The western clawed frog (Xenopus tropicalis) is a species of frog in the family Pipidae, also known as tropical clawed frog. It is the only species in the genus Xenopus to have a diploid genome. Its genome has been sequenced, making it a significant model organism for genetics that complements the related species Xenopus laevis (the African clawed frog), a widely used vertebrate model for developmental biology. X. tropicalis also has a number of advantages over X. laevis in research, such as a much shorter generation time (<5 months), smaller size (4–6 cm (1.6–2.4 in) body length), and a larger number of eggs per spawn. It is found in Benin, Burkina Faso, Cameroon, Ivory Coast, Equatorial Guinea, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Nigeria, Senegal, Sierra Leone, Togo, and possibly Mali. Its natural habitats are subtropical or tropical moist lowland forests, moist savanna, rivers, intermittent rivers, swamps, freshwater lakes, intermittent freshwater lakes, freshwater marshes, intermittent freshwater marshes, rural gardens, heavily degraded former forests, water storage areas, ponds, aquaculture ponds, and canals and ditches.

Description The western clawed frog is a medium-sized species with a somewhat flattened body and a snout-vent length of 28 to 55 mm (1.1 to 2.2 in), females being larger than males. The eyes are bulging and situated high on the head and there is a short tentacle just below each eye. A row of unpigmented dermal tubercles runs along the flank from just behind the eye, and are thought to represent a lateral line organ. The limbs are short and plump, and the fully webbed feet have horny claws. The skin is finely granular. The dorsal surface varies from pale to dark brown and has small grey and black spots. The ventral surface is dull white or yellowish with some dark mottling.

Distribution and habitat The western clawed frog is an aquatic species and is found in the West African rainforest belt with a range stretching from Senegal to Cameroon and eastern Zaire. It is generally considered a forest-dwelling species and inhabits slow-moving streams, but it is also found in pools and temporary ponds in the northern Guinea and Sudan savannas.

Biology In the dry season, this frog lives in shallow streams and hides under tree roots, under flat stones, or in holes in the riverbank. It feeds primarily on earthworms, insect larvae and tadpoles. When the rainy season starts it migrates across the forest floor at night to find temporary pools. Spawning may take place in large pools with much vegetation, but tadpoles are also sometimes found in muddy pools with no vegetation. Single eggs may be attached to plants or they may float. The tadpoles have broad mouths and no jaws, but have long tentacles on their upper lips. The ventral fins of their tails are broader than the dorsal ones. Their body colour is generally orange and the tail transparent but in darker locations the tail may be blackish. The tadpoles feed by filtering zooplankton from the water. In large water bodies, they may form dense swarms. Metamorphosis takes place when the tadpoles measure about 5 cm (2 in) in length.

Sex determination Sex determination in the vast majority of amphibians is controlled by homomorphic (morphologically indistinguishable) sex chromosomes. As a result of this difficulty in sex chromosome identification, only a relatively small proportion of anuran species that have been karyotyped have also had their sex chromosomes identified. Of the species in the genus Xenopus, all have homomorphic sex chromosomes. Additionally, the DM-W gene on the W chromosome in some Xenopus species is the only sex-determining gene that has been identified in amphibians. This DM-W gene was first identified in X. laevis, however it is not found in X. tropicalis. Experimentation involving sex-reversed individuals, gynogenesis, triploids, and conventional crosses, has determined that X. tropicalis has three sex chromosomes: Y, W, and Z. These three sex chromosomes produce three different male genotypes, YW, YZ, and ZZ (all are phenotypically identical) and two different female genotypes, ZW, and WW (all are phenotypically identical). As a result, offspring of X. tropicalis can have sex ratios that differ from the commonly known 1:1 usually found in species with only two different sex chromosomes. For example, offspring resulting from a ZW female and a YZ male will have a sex ratio of 1:3 females to males and offspring resulting from a WW female and a ZZ male will be all female. As a result of this sex determination system, both male and female X. tropicalis can be either heterogametic or homogametic which is extremely rare in nature. The exact genetic mechanism and the exact alleles underlying this system is not yet known. One possible explanation is that the W chromosome contains a female-determining allele that has function that is not found on the Z chromosome while the Y chromosome contains an allele that acts a negative regulator that is dominant over the female-determining allele on the W chromosome. Although X. tropicalis does have these three sex chromosomes, the frequency of these three sex chromosomes is not evenly distributed among this species' populations throughout its natural range. The Y chromosome has been identified from two localities in Ghana and in a laboratory strain that originated in Nigeria and the Z chromosome has been confirmed to exist in individuals from western and eastern Ghana. Additionally, all three sex chromosomes have been found to exist together in X. tropicalis populations in Ghana and potentially elsewhere in its range as well. Additionally, having irregular sex ratios in offspring is generally thought to be disadvantageous so whether or not the existence of three sex chromosomes in X. tropicalis is evolutionarily stable or an indication that the species is going through a sex chromosome transition (turnover), is still a question. It seems likely that the emergence of the Y chromosome is the most recent event in the evolution of this species' sex chromosomes. It is possible that in the future extinction of the Z chromosome would make it so that the W chromosome transitions into a X chromosome making this species with sex determined by an XY system. It is also possible that if the Y chromosome were to go extinct, this species will have reverted to using an ancestral ZW system.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Western clawed frog

Start with the simplest possible case. Write down what Western clawed frog claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Western clawed frog before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Western clawed frog ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Western clawed frog

In research: Western clawed frog appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Western clawed frog in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Western clawed frog is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amphibians described in 1864, Animal models, IUCN Red List least concern species, so understanding it makes those chapters shorter.
In everyday life: Look for Western clawed frog outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Western clawed frog in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Western clawed frog means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Western clawed frog out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Western clawed frog in simple terms?

The western clawed frog (Xenopus tropicalis) is a species of frog in the family Pipidae, also known as tropical clawed frog. It is the only species in the genus Xenopus to have a diploid genome.

Why does Western clawed frog matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Western clawed frog?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Western clawed frog.