Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of stem cells in the adult organism.
Planarians (triclads) are free-living flatworms of the class Turbellaria., order Tricladida, which includes hundreds of species, found in freshwater, marine, and terrestrial habitats. Planarians are characterized by a three-branched intestine, including a single anterior and two posterior branches. Their body is populated by adult stem cells called neoblasts, which planarians use for regenerating missing body parts. Many species are able to regenerate any missing organ, which has made planarians a popular model in research of regeneration and stem cell biology. The genome sequences of several species are available, as are tools for molecular biology analysis.
Acoelomorpha is a subphylum of very simple and small soft-bodied animals with planula-like features which live in marine or brackish waters. They usually live between grains of sediment, swimming as plankton, or crawling on other organisms, such as algae and corals. With the exception of two acoel freshwater species, all known Acoelomorphs are marine.
Biological immortality is a state in which the rate of mortality from senescence is stable or decreasing, thus decoupling it from chronological age. Various unicellular and multicellular species, including some vertebrates, achieve this state either throughout their existence or after living long enough. A biologically immortal living being can still die from means other than senescence, such as through injury, poison, disease, predation, lack of available resources, or changes to environment.
A blastema is a mass of cells capable of growth and regeneration into organs or body parts. The changing definition of the word "blastema" has been reviewed by Holland (2021). A broad survey of how blastema has been used over time brings to light a somewhat involved history. The word entered the biomedical vocabulary in 1799 to designate a sinister acellular slime that was the starting point for the growth of cancers, themselves, at the time, thought to be acellular, as reviewed by Hajdu. Then, during the early nineteenth century, the definition broadened to include growth zones in healthy, normally developing plant and animal embryos. Contemporaneously, cancer specialists dropped the term from their vocabulary, perhaps because they felt a term connoting a state of health and normalcy was not appropriate for describing a pathological condition. During the middle decades of the nineteenth century, Schleiden and Schwann proposed the cell theory, and Remak and Virchow insisted that cells can only be generated by division of existing ones. Consequently, the conception of the blastema changed from acellular to cellular. More specifically, the term came to designate a population of embryonic cells that gave rise to a particular tissue. In short, the term blastema started being used to refer to what modern embryologists increasingly began calling a rudiment or Anlage. Importantly, the term blastema did not yet refer to a mass of undifferentiated-looking cells that accumulates relatively early in a regenerating body part. For instance, Morgan (1900), does not use the term even once in his classic book, “Regeneration.” It was not until the eve of World War 1 that Fritsch introduced the term blastema in the modern sense, as now used by contemporary students of regeneration. Currently, the old usage of blastema to refer to a normal embryological rudiment has largely disappeared.
Dugesia is a genus of dugesiid triclads that contains some common representatives of the class Turbellaria. These common flatworms are found in freshwater habitats of Africa, Eurasia, and Australia. Dugesia is best known to non-specialists because of its regeneration capacities.
Genome-based peptide fingerprint scanning (GFS) is a system in bioinformatics analysis that attempts to identify the genomic origin of sample proteins by scanning their peptide-mass fingerprint against the theoretical translation and proteolytic digest of an entire genome. This method is an improvement from previous methods because it compares the peptide fingerprints to an entire genome instead of comparing it to an already annotated genome. This improvement has the potential to improve genome annotation and identify proteins with incorrect or missing annotations.
Continenticola is a clade that includes the land planarians (Geoplanidae) and the freshwater triclads.
Dugesiidae is a family of freshwater planarians distributed worldwide. The type genus is Dugesia Girard, 1850.
Girardia is a genus of freshwater planarians belonging to the family Dugesiidae.
Schmidtea is a genus of freshwater triclads. Species of the genus Schmidtea are widely used in regeneration and developmental studies.
Dugesia notogaea is a species of dugesiid triclad that inhabits freshwater bodies of north Queensland, Australia.
Dugesia tubqalis is a species of dugesiid triclad that inhabits springs of Morocco. It is named after the Toubkal peak, the highest in the Atlas Mountains. It has been found between 1,702 and 2,164 m of altitude.
Dugesia sicula is a species of dugesiid triclad that lives in freshwater bodies of the Mediterranean Basin, where it is widely distributed. It has been reported from Sicily, Elba and Mallorca, Eivissa, Sardinia, Algeria, Tunisia, Morocco and Crete.
Dugesia japonica is a species of freshwater planarian that inhabits freshwater bodies of East Asia, including Japan, Korea, Taiwan, China and northeastern Siberia. However, molecular studies suggest that Dugesia japonica is polyphyletic and different populations across its area of occurrence constitute distinct species.
Cura is a genus of freshwater flatworm (triclad)s belonging to the family Dugesiidae.
Neppia is a genus of dugesiid triclad that is found in South America, Subantarctic region, Africa, Tasmania and New Zealand.
Dugesia subtentaculata is a species of planarian that inhabits the freshwater of Southern France, several localities on the Iberian Peninsula, Mallorca, Morocco and Algeria.
Neoblasts (ˈniːəʊˌblæst) are adult stem cells found in planarian flatworms. They are the only dividing planarian cells, and they produce all cell types, including the germline. Neoblasts are abundant in the planarian parenchyma, and comprise up to 30 percent of all cells. Following injury, neoblasts rapidly divide and generate new cells, which allows planarians to regenerate any missing tissue.
Planarian secretory cell nidovirus (PSCNV) is a virus of the species Planidovirus 1, a nidovirus notable for its extremely large genome. At 41.1 kilobases, it is the largest known genome of an RNA virus. It was discovered by inspecting the transcriptomes of the planarian flatworm Schmidtea mediterranea and is the first known RNA virus infecting planarians. It was first described in 2018.
