The Naked Scientists

The Naked Scientists Forum

Author Topic: want a new starfish..cut an arm off one!  (Read 17997 times)

paul.fr

  • Guest
want a new starfish..cut an arm off one!
« on: 28/03/2007 09:56:25 »
is it true that if a starfish can "loose" one if it's arms and a new starfish will grow from that arm? if it is how does that happen?


 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
want a new starfish..cut an arm off one!
« Reply #1 on: 28/03/2007 10:12:09 »
I did not know that! So does a starfish have stem cells  that reproduce like the ones in our nasal passages in order for it to regrow its missing limb? WAIT WAIT WAIT you mean will a whole new starfish grow from that missing joint or arm?
 

paul.fr

  • Guest
want a new starfish..cut an arm off one!
« Reply #2 on: 29/03/2007 01:51:11 »
I did not know that! So does a starfish have stem cells  that reproduce like the ones in our nasal passages in order for it to regrow its missing limb? WAIT WAIT WAIT you mean will a whole new starfish grow from that missing joint or arm?

Yes, a whole new starfish!
 

Offline WylieE

  • Sr. Member
  • ****
  • Posts: 236
    • View Profile
want a new starfish..cut an arm off one!
« Reply #3 on: 29/03/2007 02:29:24 »
There's an old story that years ago that Gulf Coast shellfish fishermen (they aren't very generous  ::)) would cut starfish up when they hauled them in in their nets- to try to reduce the competition (starfish love shellfish).  They didn't realize they might be making a lot more of them.
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
want a new starfish..cut an arm off one!
« Reply #4 on: 29/03/2007 03:44:00 »
Oh That is cool, what happens to the old starfish does it drop off or do they stay attached??
 

Offline Supercryptid

  • Hero Member
  • *****
  • Posts: 606
    • View Profile
    • http://www.angelfire.com/sc2/Trunko
want a new starfish..cut an arm off one!
« Reply #5 on: 30/03/2007 06:43:04 »
A new starfish can only regrow from a severed limb if that limb still retains a piece of the starfish's central region. A piece of flesh cut off from the very tip of the limb with not grow into a new starfish. The old starfish <i>can</i> heal from such an injury, however.

Also, sponges can regenerate far better than starfish can. A sponge can be sliced into any number of pieces all the way down to the cellular level and still reform itself. If a single cell is removed from a sponge and cultivated on its own, it will grow into an entirely new sponge.
 

paul.fr

  • Guest
want a new starfish..cut an arm off one!
« Reply #6 on: 30/03/2007 09:58:50 »
Very interesting, Supercryptid.

Fascinating how this works, i wonder why they have this ablitiy. is it because they do not reproduce too well? Come to think of it, who do they reproduce?
 

Offline Biology Guy

  • Jr. Member
  • **
  • Posts: 11
    • View Profile
want a new starfish..cut an arm off one!
« Reply #7 on: 30/03/2007 10:27:17 »
I believe sponges reproduce asexually by "cutting off" a piece of themselves, as was described above. This would then grow into a new sponge.

Starfish can both sexually and asexually reproduce. However, as was mentioned above, it can only reproduce asexually if they loose an arm when that arm retains a piece of the central region.

 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
want a new starfish..cut an arm off one!
« Reply #8 on: 30/03/2007 16:38:43 »
 That is really interesting. How are they able to do that? what exactly is the process? That is facinating.As I asked before Is it like stem cell regeneration or what? Do all living things produce stem cells,? I really do not know!
 

Offline Seany

  • Neilep Level Member
  • ******
  • Posts: 4209
  • Live your life to the full!
    • View Profile
want a new starfish..cut an arm off one!
« Reply #9 on: 10/04/2007 11:51:43 »
Wow, that is cool. So, if we figure out how the stem cells work in the starfish, we may just be able to do the same with humans, as we have been trying to do for the last 10 years maybe?
 

another_someone

  • Guest
want a new starfish..cut an arm off one!
« Reply #10 on: 10/04/2007 12:33:01 »
Wow, that is cool. So, if we figure out how the stem cells work in the starfish, we may just be able to do the same with humans, as we have been trying to do for the last 10 years maybe?

If you cut up a human, leaving part of the central region attached to each part (such as one part had the head, the other the heart), neither part would live long enough to regrow the other, even if it had the capacity to do it.

Mammals have a far more complex set of interdependent specialised organs that cannot simply be separated apart and allow the parts to survive and regrow.

One question that does arise from regrowth of simple animals from their parts is whether the regrown animal is of the same age as the original (the current problems we have with cloning regarding our inability to reset the the cellular biological clock, so the clone is born with the cellular age of its parent)?
 

paul.fr

  • Guest
want a new starfish..cut an arm off one!
« Reply #11 on: 10/04/2007 13:23:16 »
One question that does arise from regrowth of simple animals from their parts is whether the regrown animal is of the same age as the original (the current problems we have with cloning regarding our inability to reset the the cellular biological clock, so the clone is born with the cellular age of its parent)?

an interesting point, George.

but if this how starfish reproduce naturally, i would guess (guess) the starfish are regrown as infants. my thinking for this is:

if the first starfish lives to 5 years and then has a baby starfish via losing a tenticle that baby would be 5 at the start of it's life cycle. if this one went on to have grandstarfish! surely they would be at deaths door when they were born.

like i said, only a quick guess.
 

another_someone

  • Guest
want a new starfish..cut an arm off one!
« Reply #12 on: 10/04/2007 13:55:42 »
Apparently starfish do have sexual reproductive mechanisms (and produce larvae), although some species are able to reproduce asexually (I have not yet ascertained whether all species are capable of sexual reproductions, or whether some species will exclusively reproduce asexually).

http://www.vsf.cape.com/~jdale/science/reproduction.htm
Quote
Starfish Reproduction

Starfish commonly reproduce by free-spawning: releasing their gametes into the water where they hopefully are fertilized by gametes from the opposite sex. To increase their chances of fertilization, starfish probably gather in groups when they are ready to spawn, use environmental signals to coordinate timing (day length to indicate the correct time of the year, dawn or dusk to indicate the correct time of day), and may use chemical signals to indicate their readiness to each other.

Fertilized eggs grow into bipinnaria and later into brachiolaria larvae, which either grow using a yolk or by catching and eating other plankton. In either case, they live as plankton, suspended in the water and swimming by using beating cilia. The larvae are bilaterally symmetric unlike adults, they have a distinct left and right side. Eventually, they undergo a complete metamorphosis, settle to the bottom, and grow into adults.

Bipinnaria larvae of a starfish.

Brachiolaria larvae of a starfish.
Some species of starfish brood their young: the males spawn gametes which fertilize eggs held by the females. The females may hold the eggs on their surface, in the pyloric stomach (as in Leptasterias tenera), or even attach them to the ground (as in Asterina gibbosa). Brooding is especially common in polar and deep-sea species, environments less favorable for larvae.

Male and female starfish are not distinguishable from the outside; you need to see the gonads or be lucky enough to catch them spawning. The gonads are located in each arm, and release gametes through gonoducts located on the central body between the arms.


http://en.wikipedia.org/wiki/Starfish
Quote
Starfish are capable of both sexual and asexual reproduction. Individual starfish are male or female. Fertilization takes place externally, both male and female releasing their gametes into the environment. Resulting fertilised embryos form part of the zooplankton.

Starfish are developmentally (embryologically) known as deuterostomes. Their embryo initially develops bilateral symmetry, indicating that starfish probably share a common ancestor with the chordates, which includes the fish. Later development takes a very different path however as the developing starfish settles out of the zooplankton and develops the characteristic radial symmetry. Some species reproduce cooperatively, using environmental signals to coordinate the timing of gamete release; in other species, one to one pairing is the norm.

Some species of starfish also reproduce asexually by fragmentation, often with part of an arm becoming detached and eventually developing into an independent individual starfish. This has led to some notoriety. Starfish can be pests to fishermen who make their living on the capture of clams and other mollusks at sea as starfish prey on these. The fishermen would presumably kill the starfish by chopping them up and disposing of them at sea, ultimately leading to their increased numbers until the issue was better understood. A starfish arm can only regenerate into a whole new organism if some of the central ring of the starfish is part of the chopped off arm.
« Last Edit: 10/04/2007 14:08:42 by another_someone »
 

Offline Seany

  • Neilep Level Member
  • ******
  • Posts: 4209
  • Live your life to the full!
    • View Profile
want a new starfish..cut an arm off one!
« Reply #13 on: 10/04/2007 15:18:56 »
Yep.. Interesting
 

The Naked Scientists Forum

want a new starfish..cut an arm off one!
« Reply #13 on: 10/04/2007 15:18:56 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums