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Γιγαντιαίο, Απειλητικό, Χωροκατακτητικό Αλλόχθονο Σκουλήκι στη Γαλλία, συγκλονίζει τους βιολόγους με τις υπερφυσικές του δυνατότητες





Γιγαντιαία σκουλήκια του είδους Hammerhead Worms έχουν εισβάλει στη Γαλλία.
Πρόκειται για ξένα είδη που είναι χωροκατακτητικά ( εισβλητικά) και τουλάχιστον για δυο δεκαετίες (από το 1999) περιπλανώνται κρυφά στα γαλλικά οικοσυστήματα.
Μόνο πρόσφατα ξεκίνησε η έρευνα για την έκταση της εισβολής τους και για το πόσο απειλούν την αφθονία και τη βιοποικιλότητα των γηγενών ασπόνδυλων.
Το είδος Diversibipalium multilineatum είναι ένα από τα πέντε χωροκατακτητικά είδη "hammerhead flatworm" σκουληκιών που εγκαταστάθηκαν στη Γαλλία (in metropolitan France and overseas French territories)

Τα Hammerhead Worms μοιάζουν με δυνατούς μεγάλους γαιοσκώληκες, έχουν μυώδη, πολύχρωμα σώματα που ξεπερνούν τα 40 εκατοστά σε μήκος και επιμήκη κεφαλή που μοιάζει με την κεφαλή του σφυροκέφαλου "hammerhead" καρχαρία.
Ο καθηγητής Jean-Lou Justine, καθηγητής στο Τμήμα "Department of Systematics and Evolution" του Εθνικού Μουσείου Φυσικής Ιστορίας στο Παρίσι, είπε (με email) στο Live Science, ότι αν και πολλά είδη flatworms είναι ιθαγενή στην Ευρώπη, οι γιγάντιοι σκώληκες "hammerhead flatworms" βρίσκονται συνήθως μόνο στις θερμές περιοχές της Ασίας. Κατάφεραν να εισαχθούν σε ξένα ενδιαιτήματα της Ευρώπης, ως λαθρεπιβάτες στο χώμα, σε διεθνείς μεταφορές φυτών.
Διαθέτουν μια εκπληκτική υπερδύναμη: την αναγεννητική ικανότητα. Αναγεννιούνται πλήρως από τα ακρωτηριασμένα κομμάτια τους. Αυτά τα κομμάτια μπορούν να επανέλθουν σε πλήρη σκουλήκια, ακόμα και αν ένα κομμάτι αντιπροσωπεύει μόλις το 1/300 του σώματος του σκουληκιού.
Will Two Worms Grow from a Worm Cut in Half? (24-7-2013)
ο απλός γαιοσκώληκας δεν θα τα καταφέρει, αλλά ένα είδος, το planarian flatworm, διαθέτει αυτή την αναγεννητική ικανότητα.


15-2-13
Planarians are worms that can re-form from tiny segments.
https://www.livescience.com/27176-animals-clues-regeneration-nigms.html


 

όταν ένα flatworm αναγεννήσει το κεφάλι του μετά από αποκεφαλισμό, το πλάσμα διατηρεί αξιοσημείωτα όλες του τις παλιές αναμνήσεις, σύμφωνα με έρευνα που δημοσιεύτηκε στο τεύχος του περιοδικού της πειραματικής βιολογίας του Ιουλίου 2013.
πηγή
https://www.livescience.com/38371-two-worms-worm-cut-in-half.html
Σε μια περίπτωση, ένα flatworm σκουλήκι που έστειλαν στο διάστημα μεγάλωσε μια δεύτερη κεφαλή, μετά την αποκοπή της ουράς του.
Worm Grows 2 Heads in Space, Surprising Scientists
An amputated flatworm fragment sent to space regenerated into a double-headed worm, a rare spontaneous occurrence of double-headedness.Credit: Junji Morokuma/Allen Discovery Center at Tufts University
https://www.livescience.com/59461-worm-grows-two-heads-in-space.html

Και σε άλλη μελέτη, οι ερευνητές πέτυχαν την αναγέννηση των σκουληκιών έτσι ώστε μετά την ακρωτηριασμό των κεφαλών των ζώων, να αναπαράγουν κεφάλια και εγκεφάλους που μοιάζουν με αυτά διαφορετικών ειδών .
24-11-2015
Franken Flatworms Grow Heads and Brains of Other Species
Call them Franken flatworms. Scientists have created worms with the heads and brains of other species just by manipulating cell communication
https://www.livescience.com/52905-franken-flatworms-grow-heads-brains-of-other-species.html

Ένας λόγος για τον οποίο τα τεράστια είδη flatworms που αναφέρθηκαν στη μελέτη, είναι εξαιρετικά επιτυχημένοι εισβολείς είναι ότι αναπαράγονται ασεξουαλικά , γεγονός που επιτρέπει σε ένα άτομο να παράγει πολλούς απογόνους αμέσως, δήλωσε ο Justine στο Live Science.
"Ένας άλλος λόγος είναι η απουσία θηρευτών", πρόσθεσε ο Justine. " τα Land flatworms παράγουν χημικά που τους δίνουν μια δυσάρεστη γεύση", έτσι ώστε οι θηρευτές να μην τρώνε αυτά τα σκουλήκια.

Eδώ και σχεδόν 20 χρόνια, εντοπίστηκαν πέντε χωροκατακτητικά είδη σκουληκιών σε μέρη της Γαλλίας και στα γαλλικά εδάφη, σύμφωνα με τη νέα μελέτη που συγκεντρώνει αναφορές παρατηρήσεων από το 1999
για πάνω από τέσσερα χρόνια, ο Justine και οι συνεργάτες του διερεύνησαν 111 αρχεία και παρατηρήσεις που συγκεντρώθηκαν από εθελοντές από παρατηρήσεις σε κήπους, από το 1999 έως το 2017.
Οι αναφορές περιγράφουν δεκάδες, ακόμη και εκατοντάδες flatworms σε μεμονωμένες τοποθεσίες, ανέφεραν οι επιστήμονες. Οι ερευνητές προσδιόρισαν πέντε μη-ιθαγενή είδη του τεράστιου flatworm", που διανέμονται στην ηπειρωτική Γαλλία και στα γαλλικά υπερπόντια εδάφη, συμπεριλαμβανομένων των γαλλικών νησιών της Καραϊβικής, της Γαλλικής Πολυνησίας και της Γαλλικής Γουιάνας.

Τα ευρήματα δημοσιεύθηκαν στις 22 Μαΐου, στο περιοδικό PeerJ.
https://peerj.com/articles/4672.pdf

https://www.livescience.com/62635-hammerhead-flatworms-invade-france.html
http://hellenicrevenge.blogspot.com/2018/05/blog-post_26.html





ΦΩΤΟ: Two of the flatworm species in the Diversibipalium genus — one black, found in France, and one an iridescent blue, found on the island of Mayotte — are likely newfound species, according to the study.


The mystery of why some animals can regenerate body parts while others cannot has long puzzled scientists, but three new studies have brought the issue to a head.

Three different research groups studied why some species of flatworms can regenerate entire heads and tails after being cut into pieces, while other species of worm only partially regenerate their body parts. By activating a single gene in the cascade of signals involved in regeneration, the researchers restored the worms' ability to grow new heads.
"In flatworms, you can cut out a single piece from any part of the worm, and somehow, magically, it turns itself into a worm," said molecular biologist Jochen Rink, who led one of the studies. The question is, "Why can some animals regenerate while others can't?" said Rink, of the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany.



How Animals Offer Clues to Regeneration

With the goal of finding ways to regenerate lost or injured body parts, researchers funded by the National Institutes of Health are exploring the strategies that some organisms use to regrow missing cells, organs and appendages. Here are a few examples.
Re-Forming From Stem Cells
Planarians are tiny freshwater flatworms — about the size of toenail clippings — that can re-form from slivers 1/300th of their original size. To do this, planarians use stem cells, called cNeoblasts, that have the ability to become almost any cell type in the body. Researchers at the Whitehead Institute for Biomedical Research studied the genes that are active in these stem cells to determine which of them are key players.


Planarians are worms that can re-form from tiny segments.
Planarians are worms that can re-form from tiny segments.
Credit: Alejandro Sánchez Alvarado, Stowers Institute for Medical Research 

The researchers identified 10 “renewal” genes that help the stem cells create more like themselves. In addition, the scientists pinpointed two genes that trigger stem cells to become different types and also have roles in renewal. Because half of planarians’ genes have parallels in people, the scientists aim to use their findings to find regenerative genes in human embryonic stem cells.
Ringers in Regeneration
Zebrafish, blue-and-white-striped fish that grow to be about 1.5 inches long, can regrow fins. To study how, scientists at Duke University Medical Center generated zebrafish with depleted levels of cells responsible for creating bone. These cells, called osteoblasts, normally increase in number after a fish loses a fin. The researchers expected that when osteoblast-deficient fish lost fins, they wouldn’t be able to regenerate them as quicklyas those with normal levels of osteoblasts, if they could regenerate their fins at all. Surprisingly, all of the fish in the experiment regrew their fins, with recovery occurring at normal rates. Learning more about this process could aid the development of therapies for bone injury or loss in humans.


About an inch and half, zebrafish can regrow lost fins.
About an inch and half, zebrafish can regrow lost fins. 
Credit: Wikimedia Commons. 

Sticking with the Same
Scientists at Washington University in St. Louis identified another zebrafish regeneration strategy by tracking how individual cells behaved in the stump of an amputated fin. One possibility was that adult nerve, bone and skin cells that make up the fin would revert into stem cells with the potential to become other cell types. However, this study showed that adult cells maintained their identities during regeneration, with skin cells in the stump only giving rise to skin cells in the new fin. This discovery suggests that inducing the cells that are already present to grow again could be an additional approach to replacing lost or injured tissues. 


While ear tissue doesn't normally grow back completely in mice, the lack of one gene makes ears heal without scars.
While ear tissue doesn't normally grow back completely in mice, the lack of one gene makes ears heal without scars. 
Credit: Ellen Heber-Katz, The Wistar Institute. 

Gene Off, Healing On
Yet another technique for promoting regeneration might be found in turning genes off. Several years ago, researchers at The Wistar Institute discovered that inactivating a single gene allowed holes in mouse ears to close without scarring. The researchers determined that this breed of mice has an inactive version of a gene involved in regulating cell growth and division. The finding offers new insight into regeneration in a mammal and could guide the direction of future research.
While these results hold promise for the development of treatments to replace or repair human tissue, they also illustrate the complexity of regeneration and raise such questions as how organisms know what’s missing and how they prevent replacement tissues from cancerlike overgrowth.
This Inside Life Science article was provided to LiveScience in cooperation with the National Institute of General Medical Sciences, part of the National Institutes of Health.

Franken Flatworms Grow Heads and Brains of Other Species

Call them Franken flatworms. Scientists have created worms with the heads and brains of other species just by manipulating cell communication.
The research is an example of how development is controlled by more than genetics alone. The researchers did not alter the flatworms' DNA in any way, but instead manipulated proteins that control conversations between cells.
"It is commonly thought that the sequence and structure of chromatin — the material that makes up chromosomes — determine the shape of an organism, but these results show that the function of physiological networks can override the species-specific default anatomy," study researcher Michael Levin, a biologist at Tufts University, said in a statement. [See Photos of the Franken Flatworms with Different Heads, Brains]
The changes are temporary for the worms, whose heads begin to revert back to their original shapes in weeks. But researchers hope the findings will lead to treatments for birth defects and even regenerative medicine, which aims to replace or rebuild damaged tissues and organs.
The researchers studied a small freshwater flatworm, Girardia dorotocephala, which is known for being able to regenerate lost tissues. These flatworms retain a large number of cells called neoblasts, which are totipotent stem cells, meaning they can become any cell type in the body. In humans, cells are totipotent only in the first days of embryonic development.
First, the scientists cut off the heads of their lab specimens. Next, to alter the flatworm's regenerating head, Levin and his colleagues interrupted protein channels called gap junctions. Cells send electrical impulses through these junctions in order to communicate. The researchers found that they could easily nudge the worm to develop head and brain shapes similar to those of other closely related flatworm species.
Normally, G. dorotocephala sports a pointy head with two elongated, earlike projections (called auricles) next to the eyes. After treatment, some of the worms developed their normal heads, while others grew rounded heads like those of S. mediterranea; heads with thick necks and pointy, catlike "ears" like those of P. felina; or triangular heads like those of D. japonica.
The brains seemed to follow suit with the altered head shape, so that flatworms that regenerated a head shaped like that of D. japonica, for instance, also showed brain morphologies that were shorter and wider than those of G. dorotocephala and more characteristic of D. japonica.
The farther two species were from each other on the evolutionary family tree, the harder it was to induce this mix-and-match effect, the researchers reported online Nov. 24 in the International Journal of Molecular Sciences.
"These findings raise significant questions about how genes and bioelectric networks interact to build complex body structures," Levin said. If genes provide a blueprint for an organism's body, cells are like the construction workers required to turn the plan into a structure — and gap junctions are the walkie-talkies these workers use to communicate. Disrupt the communications, and you can disrupt the building process.
G. dorotocephala remained altered for only a limited amount of time before its neoblasts took over and reasserted the old head and brain shapes. However, Levin's lab previously engineered another species of flatworm to grow two heads and stay that way.

Getting a Head: How Worms Regenerate Lost Tissue



Getting a Head: How Worms Regenerate Lost Tissue
Planarians are worms that can re-form from tiny segments.
Credit: Daryl H | Shutterstock

The mystery of why some animals can regenerate body parts while others cannot has long puzzled scientists, but three new studies have brought the issue to a head.
Three different research groups studied why some species of flatworms can regenerate entire heads and tails after being cut into pieces, while other species of worm only partially regenerate their body parts. By activating a single gene in the cascade of signals involved in regeneration, the researchers restored the worms' ability to grow new heads.
"In flatworms, you can cut out a single piece from any part of the worm, and somehow, magically, it turns itself into a worm," said molecular biologist Jochen Rink, who led one of the studies. The question is, "Why can some animals regeneratewhile others can't?" said Rink, of the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany.
Undead head
To find out the answer to this question, the three groups studied several closely related species of flatworm, or planarian. Some species, such as Schmidtea mediterranea, have superb regeneration abilities. If you cut these worms anywhere along their length, the head portion will grow a new tail, and the tail portion will grow a new head. [Image Gallery: Remarkable Bionic Animals]
In contrast, species such as Dendrocoelum lacteum have less capacity for regeneration. If you cut these worms within the quarter of their body closest to their head, they will form two complete worms, but if you cut them farther down, the intact tail portion will not regrow a head.
The process of growing a new head, complete with a brain and eyes, is complex, to say the least. Previous research has shown that severing a body part sets off a chain of signals in stem cells, the biological putty that can develop into any tissue type. Together, these signals act as a molecular switch: Activating the signals leads to the creation of a new tail, whereas blocking them enables a new head to develop.   
Now, using cutting-edge genetic-sequencing technologies, the researchers determined which genes were active, turning on regeneration signals, in the flatworms that could generate new noggins compared with those that couldn't.
None of the genes associated with head regeneration was active in the tail halves of those worms that only partially regenerated, the studies found. "It was as if the [tail] piece never made the decision to initiate head regeneration," Rink told LiveScience.
Next, the researchers artificially blocked the molecular signals that cause tail regeneration. As a result, the worms that previously lacked the ability to regenerate heads were able to grow new ones.


The planarian species Dendrocoeulum lacteum is incapable of regenerating a lost head. This sample, however, was genetically modified – head regrowth was reactivated.
The planarian species Dendrocoeulum lacteum is incapable of regenerating a lost head. This sample, however, was genetically modified – head regrowth was reactivated.
Credit: MPI-CBG, Dresden 

The idea that interfering with a single gene could overcome the blockage of head regeneration was a big surprise, said Phillip Newmark, a developmental biologist at the University of Illinois at Urbana-Champaign and leader of one of the other studies.
Rink agreed. "In order to induce this process artificially, you might think you would have to twiddle a hundred knobs at the same time — but you may have to only twiddle a few knobs," he said.
Flatworms can even be made to grow a second head in place of a tail, and each head controls half of the body. Or, you can make a worm with no head and two tails, which makes you wonder why they need a brain at all, Rink said.
Powers of regeneration
The teams can only speculate as to why some flatworm species can regenerate heads naturally but other worm species cannot. There could be trade-offs to complete regeneration ability, the researchers said. Rink speculated that some flatworms use regeneration as a method of asexual reproduction. "The animal attaches to the surface, and the head 'walks off'," he said. Other flatworms may concentrate on producing eggs for sexual reproduction, at the expense of their ability to regenerate.
Neurobiologist Alejandro Sánchez Alvarado, who was not involved in any of the studies, said the findings are important to scientists' understanding of regeneration in flatworms and the phenomenon's evolution. "The question remains whether this type of modulation may or may not explain loss or gains of regenerative capacities in animals other than [flatworms]," said Sánchez Alvarado, a neurobiologist at the Stowers Institute for Medical Research in Kansas City, Mo.
Other animals, such as certain types of salamanders and fish, can also regenerate limbs. But it's not yet clear whether they use the same "blueprint" for regeneration or whether they evolved their abilities independently, Rink said.
It's tempting to ask whether humans might benefit from these studies of tissue regeneration. But humans are very different from flatworms and don't have the ability to partially regenerate as the worms do.
"Exploring how we can translate principles derived from these studies to those of mammalian regeneration would be interesting and may eventually be beneficial for development of regenerative medicine [in humans]," said Mayumi Ito, a professor of dermatology at NYU School of Medicine who was not involved with the studies. 
All three groups' findings were detailed online today (July 24) in the journal Nature.

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