About how long does regeneration of a planarian transected horizontally require

Question

About how long does regeneration of a planarian transected horizontally require to form two complete planarians?

For what purposes is planarian regeneration studied?

How does planarian regeneration differ from that of amphibians?

TRUE OR FALSE: Planarian stem cells are different because they are always present, meaning they do not have to undergo clonal expansion before becoming active.

To what phylum do planarians belong?

Which of these areas if amputated from the remaining planarian body will not regenerate to form a new animal?

What is the population of stem cells in planarians responsible for their regenerative properties?

Explanation / Answer

If a planarian split lengthwise or crosswise will regenerate into two separate individuals. In one experiment, T.H. Morgan found that a piece corresponding to 1/279th of a planarian or a fragment with as few as 10,000 cells can successfully regenerate into a new worm within one to two weeks.

Purposes of planarian regeneration studied -Presently, regeneration is used to include multiple restorative processes manifested either as a result of physiological turnover (for example, the renewal of blood, skin and gut epithelial cells) or injury, and more recently has been used to define a branch of medical practice referred to as 'regenerative medicine'. Planarians (traditional genetic model systems), which are non-parasitic flatworms, display remarkable regenerative capacities for all of their tissues, irrespective of whether these were derived from endoderm, mesoderm or ectoderm. Because of their evolutionary position, these bilaterally symmetric, triploblastic organisms were expected to share with vertebrates a large number of the molecular and cellular processes that make form and function possible in animals. We now know that this is indeed the case, as planarians share with vertebrates all of the major developmental signaling pathways responsible for the establishment of the bilateral body plan. in addition to their remarkable powers of regeneration, and in contrast to vertebrate regeneration model systems, planarians are small (about the size of a toenail clipping), and rather easy and relatively inexpensive to rear in great numbers in the lab, allowing for genome-wide functional studies of regeneration. Planarians are also an emerging model organism for aging research. These animals have an apparently limitless regenerative capacity, and the asexual animals seem to maintain their telomerase levels throughout their lifetime, making them "effectively immortal"

Planarian regeneration differ from that of amphibians- as If you chop up a flat worm (planarian) in several bits, they will each grow into a tiny worm (scientists have even been able to grow flat worms from single cells!) but Urodele amphibians can fully regenerate their limbs, tail, jaws, and retina via epimorphic regeneration leading to functional replacement with new tissue. Limb regeneration in salamanders (and frog tadpoles and fish) occurs in three main steps. Let’s say a salamander's leg is amputated. First, a thin layer of skin quickly covers the wound, and this is a crucial difference between salamanders and most other vertebrates, which develop thick scars. Second, this skin sends chemical signals to the cells underneath to instruct them to reverse their identity (bone, muscle, nerve…) to a stem cell-like undifferentiated state. Finally, these 'dedifferentiated' cells multiply and form the blastema—a pool of cells capable of turning into any cell type that will build a new, fully functional leg. salamanders can regenerate their limbs (and some organs) over and over again.

In Planaria (Platyhelminthes) after amputation (surgical removal of all part of a limb), stump cells form a blastema formed from neoblasts, pluripotent cells found throughout the planarian body. New tissue grows from neoblasts with neoblasts comprising between 20 and 30% of all planarian cells. Recent work has confirmed that neoblasts are totipotent since one single neoblast (single pluripotent adult stem cell type) can regenerate an entire irradiated animal that has been rendered incapable of regeneration.

In salamanders after amputation, the epidermis migrates to cover the stump in 1–2 hours, forming a structure called the wound epithelium (WE). Epidermal cells continue to migrate over the WE, resulting in a thickened, specialized signaling center called the apical epithelial cap (AEC). Over the next several days there are changes in the underlying stump tissues that result in the formation of a blastema (a mass of dedifferentiated proliferating cells). As the blastema forms, pattern formation genes – such as HoxA and HoxD – are activated as they were when the limb was formed in the embryo. The positional identity of the distal tip of the limb (i.e. the autopod, which is the hand or foot) is formed first in the blastema. Intermediate positional identities between the stump and the distal tip are then filled in through a process called intercalation. Motor neurons, muscle, and blood vessels grow with the regenerated limb, and reestablish the connections that were present prior to amputation. The time that this entire process takes varies according to the age of the animal, ranging from about a month to around three months in the adult and then the limb becomes fully functional. Researchers at Australian Regenerative Medicine Institute at Monash University, have published that when macrophages, which eat up material debris, were removed, salamanders lost their ability to regenerate and formed scarred tissue instead.

Yes, Planarian stem cells are different because they are always present, meaning they do not have to undergo clonal expansion before becoming active. As Neoblasts are abundantly present throughout the mesenchyme and divide continuously. The resulting stream of progenitors and turnover of differentiated cells drive the rapid self-renewal of the entire animal within a matter of weeks.

A Planarian belong to Phylum- platyhelminthes. Planarian is one of many flatworms of the Turbellaria class. It is also the common name for a member of the genus Planaria within the family Planariidae. Sometimes it also refers to the genus Dugesia.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.