science

Schmidtea mediterranea

Schmidtea mediterranea is a science 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 Schmidtea mediterranea rather than just read about it. In short: Schmidtea mediterranea is a freshwater triclad (planarian) that lives in southern Europe and Tunisia. It is a model for regeneration, stem cells and development of tissues such as the brain and germline.

Key takeaways

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

Reference excerpt

Schmidtea mediterranea is a freshwater triclad (planarian) that lives in southern Europe and Tunisia. It is a model for regeneration, stem cells and development of tissues such as the brain and germline. It is known to be "highly regenerative" with the whole body being regeneratable.

Distribution Schmidtea mediterranea is found in some coastal areas and islands in the western Mediterranean (Catalonia, Menorca, Mallorca, Corsica, Sardinia, Sicily and Tunisia).

Ecology High water temperatures of 25–27 °C have deleterious effects on populations of S. mediterranea, while this species tolerates variations in the acidity of the water (pH 6.9–8.9) without a noticeable influence on their survival. S. mediterranea can be found with associated fauna such as gastropods, bivalves, insects, leeches, and nematodes.

Reproduction The sexual specimens of Schmidtea mediterranea produce cocoons between November and April. In May, when water temperature rises above 20 °C, they lose their reproductive apparatus. Despite this, they don't reproduce asexually (by fissiparity) during the summer months.

Regeneration Almost any piece from a Schmidtea mediterranea individual can regenerate an entire organism in a few days. This is in part enabled by the presence of abundant adult pluripotent stem cells called neoblasts. Transplantation of a single neoblast to a fatally injured animal has been shown to rescue the animal. Stem cells are intercalated between gut branches. Their niche lies between the intestine and the surface epithilium. During regeneration, stem cells appear in proximity to mmp-1+ secretory hecatonoblasts and porcupine+ intestinal cells. The hecatonoblasts are dispensable while the intestinal cells are required. Unusually, the intestinal cells do not tend to be in direct contact with the stem cells that they control (or have any cell-cell junctions), a control scheme unusual among invertebrate stem cells.

Genome A long-read genome of S. mediterranea was sequenced in 2018. Despite the 17 rounds of inbreeding, the resulting genome remained highly heterozygous, suggesting that meiotic recombination is inefficient in this species. The genome has a repetitive fraction of 61.7%. Planarian genomes in general have been difficult to assemble from short-read sequencing due to the heterozygousity, high AT content, resistance to standard DNA isolation procedures, and repeat content. There are a few previously unknown family of long terminal repeats that the author named SLF (S. mediterranea LTR family) followed by a number. Like other flatworms, S. mediterranea shows the loss of many genes that are essential to humans and mice. As with all sequenced flatworms (as of 2018), it has no recognizable form of the fatty acid synthase FASN gene, which is essential for de novo fatty acid synthesis in eukaryotes. The heme breakdown genes HMOX1 and BLVRB are missing in this worm while the heme biosynthesis pathway is known to be present from in vivo experiments. The double-strand break repair pathway is missing many parts, which on one hand makes sense given the structural divergence and repeat content of the genome, but on the other hand is unusual given the worm's resistance to γ-radiation. Also unusual is the lack of identifiable MAD1 and MAD2 genes, thought to be essential components of the spindle assembly checkpoint (SAC). However, an SAC-like function is known to occur in planarians, as Dugesia dorotocephala displays M-phase arrest upon colchicine interference of spindle function. Additional work shows that the APC/C-CDC20 remains in control of cell cycle and RZZ complex remains in control of APC/C-CDC20 despite the absence of MAD1/2.

References

External links

Schmidtea mediterranea, model planarian facts, life cycle, anatomy at GeoChemBio Archived 2010-12-30 at the Wayback Machine

Illustrations

Worked examples

Example 1 — a first encounter with Schmidtea mediterranea

Start with the simplest possible case. Write down what Schmidtea mediterranea claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Schmidtea mediterranea 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 Schmidtea mediterranea 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 Schmidtea mediterranea

In research: Schmidtea mediterranea appears in science 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 Schmidtea mediterranea 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: Schmidtea mediterranea is common in secondary-school and first-year university syllabi. It links to neighbouring topics Animal models, Animals described in 1975, Dugesiidae, so understanding it makes those chapters shorter.
In everyday life: Look for Schmidtea mediterranea 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 Schmidtea mediterranea in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Schmidtea mediterranea 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 Schmidtea mediterranea out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Schmidtea mediterranea in simple terms?

Why does Schmidtea mediterranea matter?

Because it connects several science 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 Schmidtea mediterranea?

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 Schmidtea mediterranea.