''Schmidtea mediterranea'' is a freshwater

triclad A planarian is one of the many flatworms of the traditional class Turbellaria. It usually describes free-living flatworms of the order Tricladida (triclads), although this common name is also used for a wide number of free-living platyhelm ...

that lives in southern Europe and Tunisia. It is a

model A model is an informative representation of an object, person or system. The term originally denoted the Plan_(drawing), plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a mea ...

for

regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration (ecology), the ability of ecosystems to regenerate biomass, using photosynthesis ...

stem cells In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

and development of tissues such as the brain and

germline In biology and genetics, the germline is the population of a multicellular organism's cells that pass on their genetic material to the progeny (offspring). In other words, they are the cells that form the egg, sperm and the fertilised egg. They ...

Distribution

''Schmidtea mediterranea'' is found in some coastal areas and islands in the western Mediterranean (

Catalonia Catalonia (; ca, Catalunya ; Aranese Occitan: ''Catalonha'' ; es, Cataluña ) is an autonomous community of Spain, designated as a ''nationality'' by its Statute of Autonomy. Most of the territory (except the Val d'Aran) lies on the north ...

Menorca Menorca or Minorca (from la, Insula Minor, , smaller island, later ''Minorica'') is one of the Balearic Islands located in the Mediterranean Sea belonging to Spain. Its name derives from its size, contrasting it with nearby Majorca. Its capi ...

Mallorca Mallorca, or Majorca, is the largest island in the Balearic Islands, which are part of Spain and located in the Mediterranean. The capital of the island, Palma, is also the capital of the autonomous community of the Balearic Islands. The Bal ...

Corsica Corsica ( , Upper , Southern ; it, Corsica; ; french: Corse ; lij, Còrsega; sc, Còssiga) is an island in the Mediterranean Sea and one of the 18 regions of France. It is the fourth-largest island in the Mediterranean and lies southeast of ...

Sardinia Sardinia ( ; it, Sardegna, label=Italian, Corsican and Tabarchino ; sc, Sardigna , sdc, Sardhigna; french: Sardaigne; sdn, Saldigna; ca, Sardenya, label=Algherese and Catalan) is the second-largest island in the Mediterranean Sea, after ...

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

and

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).Benazzi M, Baguñà J, Ballester R, Puccinelli I, Papa RD: Further Contribution to the Taxonomy of the ''Dugesia lugubris-polychroa Group'' with Description of ''Dugesia mediterranea'' n. sp. (Tricladida, Paludicola). Bolletino di zoologia 1975, 42(1):81-89.Ribas M: Cariologia, sistematica i biogeografia de les Planaries d'aigues dolces al Països Catalans. 1990.Baguñà J. Carranza S, Pala M, Ribera C, Giribet G, Arnedo M, Ribas M, Riutort M: From morphology and kariology to molecules. New methods for taxonomical identification of asexual populations of freshwater planarians. A tribute to Professor Mario Benazzi. Italian Journal of Zoology 1999, 66:207-214.De Vries EJ, Baguñà J, Ball IR: Chromosomal polymorphism in planarians and the plate tectonics of the western Mediterranean. Genetica 1984, 62:187-191.

Ecology

High water temperatures of 25–27 °C have deleterious effects on populations of ''S. mediterranea'', while this species tolerates variations in the

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

ity 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

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

leech Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...

es, and

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

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.

Research

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 pluripotent stem cells called neoblasts. Transplantation of a single neoblast to a fatally injured animal has been shown to rescue the animal An analysis of the genome of ''S. mediterranea'' indicated the presence of a previously unknown family of

long terminal repeat A long terminal repeat (LTR) is a pair of identical sequences of DNA, several hundred base pairs long, which occur in eukaryotic genomes on either end of a series of genes or pseudogenes that form a retrotransposon or an endogenous retrovirus or ...

s and the lack of several essential

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

s, including genes responsible for the synthesis of

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...

s and the MAD1 and MAD2 genes, which were thought to be essential components of the

spindle assembly checkpoint The spindle checkpoint, also known as the metaphase-to-anaphase transition, the spindle assembly checkpoint (SAC), the metaphase checkpoint, or the mitotic checkpoint, is a cell cycle checkpoint during mitosis or meiosis that prevents the separa ...

References

External links

Schmidtea mediterranea, model planarian facts, life cycle, anatomy at GeoChemBio
{{Taxonbar, from=Q2158498 Dugesiidae Animal models Animals described in 1975