Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: Nazer, Mr D - (NAZ ) on 09/01/2010 02:30:03
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Nazer, Mr D - (NAZ ) - Science asked the Naked Scientists:
The syphonophore, the Portuguese man of war:
This is a collection of jelly fish each having its own individual function, catching food, digestion, movement, reproduction.
I can understand that the digestive jelly fish can feed the other jelly fish but if only one of the jelly fish reproduce, then how do the other jelly fish in the colony come about?
Have I got the facts wrong, or does the reproducing jelly fish produce all of the jelly fish?
What do you think?
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Your post interested me so I searched for info. It seems you are right. I found that man o wars arent jelly fish at all (they just resemble them) and are in fact a colony of organisms-Siphonophora-each are so specialized that most lack the ability to survive on their own.They are considered on a border between a colony and a multicellular organism.The siphonophores, are an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria. They are colonial, but the colonies can superficially resemble jellyfish; although they appear to be a single organism, each specimen is actually a colony of Siphonophora. The best known species is the dangerous Portuguese Man o' War (Physalia physalis).
Siphonophores are especially scientifically interesting because they are composed of medusoid and polypoid zooids that are morphologically and functionally specialized. Siphonophores have been known to grow up to 130 feet in length.[1] Each zooid is an individual, but their integration with each other is so strong that the colony attains the character of one large organism. Indeed, most of the zooids are so specialized that they lack the ability to survive on their own. Siphonophorae thus exist at the boundary between colonial and complex multicellular organisms. Also, because multicellular organisms have cells which, like zooids, are specialized and interdependent, siphonophores may provide clues regarding their evolution.
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Your post interested me so I searched for info. It seems you are right. I found that man o wars arent jelly fish at all (they just resemble them) and are in fact a colony of organisms-Siphonophora-each are so specialized that most lack the ability to survive on their own.They are considered on a border between a colony and a multicellular organism.The siphonophores, are an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria. They are colonial, but the colonies can superficially resemble jellyfish; although they appear to be a single organism, each specimen is actually a colony of Siphonophora. The best known species is the dangerous Portuguese Man o' War (Physalia physalis).
Siphonophores are especially scientifically interesting because they are composed of medusoid and polypoid zooids that are morphologically and functionally specialized. Siphonophores have been known to grow up to 130 feet in length.[1] Each zooid is an individual, but their integration with each other is so strong that the colony attains the character of one large organism. Indeed, most of the zooids are so specialized that they lack the ability to survive on their own. Siphonophorae thus exist at the boundary between colonial and complex multicellular organisms. Also, because multicellular organisms have cells which, like zooids, are specialized and interdependent, siphonophores may provide clues regarding their evolution.
Well blow me I never knew that!! I always thought they were a jelly fish not a colony, nice info thanks! [:)]
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surprised me too!
[:)]
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i just realized i misread your question. from what i read i was geting two different explanations of their reproduction process but i think what you wish to know is that after reproduction/fertilization, budding or miotic division takes place:
1- The Portuguese Man-O-War are hermaphrodites, so each individual gonozooid consists of male and female parts. The gonozoids of the man o’ war are the polyps that are responsible for reproduction. The adult medusa releases sperm which fertilizes an egg.(i believe one site said it releases the sperm into the open ocean toward another swarm) The egg forms a larva, which finds a place to form into gonozooids. These polyp gonozooids eventually release a medusa form by asexual budding that grows into the adult medusa which started the cycle.
2-Physalia reproduction takes place mostly in the fall. Physalia are dioecious, meaning that each “individual” is either male or female. The polyps responsible for reproduction are the gonozooids, which are comprised of gonophores; sacs containing either ovaries or testes. Fertilization occurs externally when the men of war shed their gametes into the open ocean; sperm from one colony fuses with the eggs of another colony. It is unknown what causes this spawning cycle to begin. However, the release of gametes may be triggered by a chemical response due to the presence of men of war in large quantities in a single locality. This critical density is probably needed for successful fertilization. Physalia physalis also reproduces a sexually by means of budding or mitotic division.
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Nobody has answered the question, which I'll try to reformulate. The Man of War comprises four separate organisms (polyps): the sail and three zooids. Only one of these, the gonozooid, is responsible for reproduction. The gonozooid can presumably only reproduce more gonozooids, and not gastrozooids, because those are different organisms. So how exactly do more gastrozooids form? Also, how do all four polyps initially assemble to make a Man of War?
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I got this off of the Waikiki Aquariums website:
"The life cycle of the Portuguese man-of-war involves both sexual and asexual reproduction. A colony is started by a small swimming stage, called a larva, which is the product of the fusion of an egg and sperm from mature parent colonies. The larva produces a colony itself through a process called budding (asexual reproduction). The original individual divides and divides, producing more individuals, until the colony is formed. In a mature colony, specialized individuals (gonozooids) produce the eggs and sperm which will lead to more larval forms."
My understanding is that the sperm and egg come together and from that an organism forms that grows all four zooids into one larger organism.Thus, while only the gonozooid actually reproduces, from the egg and sperm union all of the zooids are formed similar to how an egg and sperm form all of the cells of multi-cellular organisms except each is its own organism. An interesting animal colony to say the least.
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There is a lot of confusion here, because physalias are very unique, and they are frequently mis-labeled as a colony of individuals. At best, they could be called a colony of zooids. These particular zooids, however, are not individuals in the robust sense of the word. The term colony here is often likened to a coral colony, but that connotes that it is a collection of asexually reproduced clones that can survive on its own if severed from the colony either artificially, or through natural, asexual, reproductive fission. As opposed to corals, physalias grow attached non-viable 'buds' that mature into specialized non-viable zooids.
Scientists have yet to understand the mechanism of zooid differentiation in the physalias, but I imagine that it is likely similar to enzymatic control of vertebrate embryonic differentiation and maturation. Chemical and spatial influences, controlled by genetic orchestration, may well lead to the specialization of zooids. But that is not to say that physalia ontogeny isn't even more unique, complex, or even more spectacular than the processes that create specialized organs of the vertebrates.
But to answer your actual question as best I can, here is what we do know. Mature physalia are either male or female (not hermaphrodites), and sexually reproduce by releasing gametes into the water, triggered usually by a large gathering of individuals. The fertilized egg becomes a protozooid, or founding polyp, that both becomes the float and initiates the budding process to create the new zooids, each genetically identical to the founder. Physalias never go through a sessile stage and strombilate a juvenile medusa, like the sychozoans, so they must grow, differentiate, and mature entirely while free-swimming.
Unfortunately, at this stage, we know very little about polyp formation in physalias. However, we do know much more about other siphonophore species. Their founding polyp forms a float, while budding a new polyp, and also grows a long, hollow stem that all succeeding polyps stay attached to. New polyps always bud from two separate locations on this stem, the first site generates swimming bells, and the second site produces an alternating succession of groups of dactylzooids, gastrozooids, and gonozooids.
The physalias grow neither a stem nor swimming bells, but we can cautiously hypothesize from their colonial hydroid cousins that many of the same mechanisms apply to physalia zooid differentiation. That is, Kevin, that your gastrozooids are budded from older polyps with the exact same genetic makeup as the 'parent' zooid, and that they are budded in subsequent groups of the three different types of zooids. The only real (meaning viable) reproduction eventually comes when the organism reaches maturity, and sexual reproduction forms a new, genetically varied "individual".
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At the risk of being over simplistic, indulge me an analogy.
Image a person, while building a house, realizes that he will need some nourishment soon. So he decides to invite three people to help him. Well, of course, he is in the middle of the forest, so there isn't anyone around to invite. But his parents taught him an ancient, secret method of cloning himself. So he clones three baby replicas of himself. He then locks them in his house because he would suffer if they weren't there to help him. He raises the first as a hunter, the second as a cook, and the third as a lover. In not much time at all, the hunter is harpooning critters in the yard and reeling them back into the kitchen. The cook is preparing and serving great meals with the catch, and the lover is watching pornos, cuz there ain't no wimmen.
Yet the house owner still isn't getting quite enough nourishment, and since he is so busy taking care of his house, he teaches his helpers how to each clone themselves. By the time the helper's clones have matured and start to help the household, the newest clones are instructed to repeat the cycle. Groups of the newest three clones keep cloning an ever newer group of three. Eventually, the house owner gets pooped, the house is completely full, and he gets tired of the free-loading porno pervs. So, when there are enough houses that have sprung up in the neighborhood, he kicks the lovers out of his house, and tells them not to come back.
The moral of the story? Cloning can help you build your house, but if you want your kids to have a chance to build a better house, ya gotta lay some pipe.
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How is the man of war a colonial organism if it all grows from the same original larva? On that basis humans would be colonies of their organs?