Isn't an embryo/foetus a parasite?

[nicolangerek]

Isn't an embryo/foetus a parasite? I understand that this could be a sensitive issue for some and I apologise if it actually offends anyone.

[Ponster]

Not exactly as parasitism normally refers to an organism living with another organism where the parasite obtains benefits from a host which it usually injures.

From www.m-w.com

[Tenar]

That depends on how you define "parasite."

Note these definitions (http://www.google.com/search?hl=en&lr=&oi=defmore&q=define:parasite).

I would say that a fetus is not a parasite, since a parasite does not benefit the host, and genetic survival is, at least theoretically, a benefit.

I suspect this one is going to end up in either Great Debates or IMHO.

[Scumpup]

I strongly suspect that there is a pro-choice argument lurking at the heart of this question. To answer the OP: No. An embryo/foetus is not a parasite. The "purpose" of living things, in the sense that they have a purpose, is to reproduce and continue the species. The mammalian reproductive strategy of the young developing inside the mother evolved because it was advantageous to the species. Parasitism, as opposed to symbiosis, is not generally thought of as advantageous to the host species.

[Paul in Qatar]

No.

[cluelessnoob]

Embryos are parasites only as much as birthed children are.

Both leech off their hosts, but as long as the host likes them or perceives some sort of benefit from them, it's all fine and dandy. Or the host is just stupid. Me, I never understood why anyone would want to have kids :)

[Padeye]

I disagree Ponster, a fetus certainly does fit the definition of parasite in the link you provided. So what? It's a semantic issue. Just because two things can fit in the same definition doesn't mean they are the same thing.

[cluelessnoob]

I disagree Ponster, a fetus certainly does fit the definition of parasite in the link you provided. So what? It's a semantic issue. Just because two things can fit in the same definition doesn't mean they are the same thing.
What? Are you saying that even if something fits a definition, that definition doesn't necessarily apply to it?

[Sattua]

The definition of parasite that I learned specified that the two organisms must be of different species--so no, a fetus is not a parasite, in my world

[Celyn]

Aha, I have long figured that they are parasites, but timidly feared to express that view.

I mean, "genetic survival" is a pretty hypothetical or indiirect "benefit", surely.

[Padeye]

What? Are you saying that even if something fits a definition, that definition doesn't necessarily apply to it?That's not what I said at all, in fact just the opposite. The fact that most people do not consider a baby to be a parasite doesn't change the fact that it does fit most definitions. Sattua's definition makes a lot more sense to me but the different species stipulation isn't in my dictionary. Any logical flaw might be in thinking that definitions alawys are or should be mutually exclusive to each other.

I may have to write a science fiction story where a creature is a true biological parasite to othes of its own species.

[Ponster]

What part of "parasite obtains benefits from a host which it usually injures." from the Merrion Webster dictionary applies to a foetus?

[cluelessnoob]

What part of "parasite obtains benefits from a host which it usually injures." from the Merrion Webster dictionary applies to a foetus?

The same way any other parasite injures its host -- it leeches off the host and drains its resources without providing any physical benefit in return.

[kunilou]

What part of "parasite obtains benefits from a host which it usually injures." from the Merrion Webster dictionary applies to a foetus?

In my copy of the Merriam Webster Collegiate Dictionary (10th edition), parasite refers to parasitisim, the definition of which is: an intimate association between organisms of two or more kinds; especially one in which a parasite obtains benefits from a host which it usually injures.

One could also read "organisms of two or more kinds" to be species per Sattua's understanding.

So if you read the definition with the assumptions that a parasite must injure the host and be of another species, no, a fetus is NOT a parasite.

Frankly, the faster this thread gets out of GQ and into GD, the better.

[Polycarp]

Try "commensalism" -- the inbetween stage between parasitism and mutualistic symbiosis. The commensal organism lives inside the host but does not injure it, other than perhaps diverting some nutrients from the host's ingestion of foodstuffs.

To me it all depends on how you interpret the definitions. There was a time, within living memory, when the potential for survival in old age depended on having at least one child willing to provide for you when you became too enfeebled to completely care for yourself. Hence pregnancy could easily be seen as a time-binding mutualism: divert your resources to the embryo now, and it will grow into an adult which will provide care for you in the future.

[Padeye]

Compare two 40 year old twins who have lead identical lives apart from one having no children and the other having given birth multiple times.

usually != always

[Little Bird]

I may have to write a science fiction story where a creature is a true biological parasite to othes of its own species.
It isn't fiction.
Deep Sea Angler Fish (http://members.fortunecity.com/anemaw/anglerfish.htm)
:)

[kanicbird]

There are some differences. One is that the 'host's' body is designed to hold, nurture and protect the 'parisite'. Also the 'parisite's' creation is from the genetic material of the mother (and father), and the begining of the parisite's life is created inside the mother.

Also the whole issue that one of the main points of life is to reproduce itself, with or without the conscent of the 'host'.

[Bosda Di'Chi of Tricor]

Isn't an embryo/foetus a parasite? I understand that this could be a sensitive issue for some and I apologise if it actually offends anyone.

Somebody's been watching the Alien Trilogy with his little brother again, hasn't he? :D

[kanicbird]

It isn't fiction.
Deep Sea Angler Fish

Interesting link, one thing about it:

similar to the mammalian foetus which is fed by being attached to its mother’s placenta

It would seem like reporduction, though having simular aspects to a parasite/host relationship, is sort of a unique seperate relationship.

Perhaps just a nitpic, but I want to make sure I's not missing anything, The mother's placenta I would think is the placenta that she had when she was attached to her mother. The placenta is the baby's placenta.

Anyway even here with the fish, it appears that there is a benefit to the host, that of reporduction.

The male continues to live as an external, parasitic, sperm-providing affixation of the female.

[nicolangerek]

I strongly suspect that there is a pro-choice argument lurking at the heart of this question. To answer the OP: No. An embryo/foetus is not a parasite. The "purpose" of living things, in the sense that they have a purpose, is to reproduce and continue the species. The mammalian reproductive strategy of the young developing inside the mother evolved because it was advantageous to the species. Parasitism, as opposed to symbiosis, is not generally thought of as advantageous to the host species.

There is nothing lurking actually. I've thought about it and wanted to hear other opinions (I am wise you see;). But unfortunately the rebuttal to your explanation has to be seen as a pro-choice: what if the mother doesn't see the unborn kid as her purpose to live. What's running through my mind is that certain mammals ( i think the zebra is one) have the option to temporarily stop the pregnancy waiting for a more opportune moment to continue gestation or to stop it altogether. In such a case I would side with your argument of invitro fertilisation as being a longer term strategy. But the issue with a human embryo is that the mother does not have that inbuilt choice.

Take the analogy which can be reminiscent of the "The Eternal Jew" propaganda documentaries so once again I have to apologise if i offend anybody - it is not my intention - but please do rebutt this argument.

A tapeworm lives off the host; it injures the host as far as depriving the host of some nutrients. an unborn kid lives off the host; it injures the host as far as depriving the host of some nutrients. If we assume the mother wants the kid, then your argument as a long term strategy holds - the foetus/embryo is not a parasite. But what if the mother/host does not want the kid - doesn't that make the foetus/embryo a parasite?

I am pro-choice in fact only because this is the way i look at the situation and am more than willing to accept a rebuttal to the above argument.

Cheers

[Scumpup]

There is nothing lurking actually. I've thought about it and wanted to hear other opinions (I am wise you see;). But unfortunately the rebuttal to your explanation has to be seen as a pro-choice: what if the mother doesn't see the unborn kid as her purpose to live. What's running through my mind is that certain mammals ( i think the zebra is one) have the option to temporarily stop the pregnancy waiting for a more opportune moment to continue gestation or to stop it altogether. In such a case I would side with your argument of invitro fertilisation as being a longer term strategy. But the issue with a human embryo is that the mother does not have that inbuilt choice.

Take the analogy which can be reminiscent of the "The Eternal Jew" propaganda documentaries so once again I have to apologise if i offend anybody - it is not my intention - but please do rebutt this argument.

A tapeworm lives off the host; it injures the host as far as depriving the host of some nutrients. an unborn kid lives off the host; it injures the host as far as depriving the host of some nutrients. If we assume the mother wants the kid, then your argument as a long term strategy holds - the foetus/embryo is not a parasite. But what if the mother/host does not want the kid - doesn't that make the foetus/embryo a parasite?

I am pro-choice in fact only because this is the way i look at the situation and am more than willing to accept a rebuttal to the above argument.

Cheers

1. In vitro fertilization is the mixing of eggs with sperm in a laboratory dish in order to achieve conception. The fertilization strategy used by humans is "in vivo fertilization" and refers only to the actual fertilization. Humans are placental mammals if we are talking about the growth and development of the embryo/foetus.
2. A human mother not perceiving her child as her sole reason for existing doesn't AFAICS somehow make a foetus into a parasite. If that were the case, then a wanted foetus is not a parasite but an unwanted one is a parasite. In other words, there is no factual answer, only subjective ones and this whole thread is in the wrong forum.

[nicolangerek]

1. In vitro fertilization is the mixing of eggs with sperm in a laboratory dish in order to achieve conception. The fertilization strategy used by humans is "in vivo fertilization" and refers only to the actual fertilization. Humans are placental mammals if we are talking about the growth and development of the embryo/foetus.
2. A human mother not perceiving her child as her sole reason for existing doesn't AFAICS somehow make a foetus into a parasite. If that were the case, then a wanted foetus is not a parasite but an unwanted one is a parasite. In other words, there is no factual answer, only subjective ones and this whole thread is in the wrong forum.

point taken although not sure about the acronym.

[kanicbird]

. If we assume the mother wants the kid, then your argument as a long term strategy holds - the foetus/embryo is not a parasite. But what if the mother/host does not want the kid - doesn't that make the foetus/embryo a parasite?

Again I don't think the desire of the parent to be a parent has anything to do with it. It is a function of our species, it's how we reproduce, it's how she passes her genetic information to future generations, her body does actively react to ensure the survival of the baby.

Morning sickness (may) happen to ensure the baby does not get nutrients that could harm the baby at critical growth stages (though I'm not sure what causes this, in other words does the baby release something that causes the mother to get sick, or does the mother).

[Colibri]

I mean, "genetic survival" is a pretty hypothetical or indiirect "benefit", surely.

Absolutely not. From the biological point of view, it is the one and only point of being alive in the first place. Life's only "purpose," if it can be said to have one, is to perpetuate itself. From a biological point of view, there is no way that your own offspring could be considered a parasite.

Whether or not a human female "wants" her offspring is entirely irrelevant with respect to whether it can be considered a parasite or not. The offspring is beneficial from the point of view of continuing her genome, and therefore is not a parasite.

[erislover]

The definition of parasite that I learned specified that the two organisms must be of different species--so no, a fetus is not a parasite, in my worldPerhaps it is just the cynic in me, but I would gather this clause is inserted specifically so that a developing offspring is not included as a parasite. Which, to me, is a little cheap, but that's what you get for looking into definitions.

[Colibri]

Perhaps it is just the cynic in me, but I would gather this clause is inserted specifically so that a developing offspring is not included as a parasite. Which, to me, is a little cheap, but that's what you get for looking into definitions.

What on Earth can you mean by this? If "parasite" means something other than developing offspring, why shouldn't the definition exclude it?

[kanicbird]

Perhaps another way of looking at it is offspring are suppose to happen for humans, tapeworms are not.

[kunilou]

Perhaps it is just the cynic in me, but I would gather this clause is inserted specifically so that a developing offspring is not included as a parasite. Which, to me, is a little cheap, but that's what you get for looking into definitions.

There's a simple enough resolution. Go find a biology textbook or dictionary written prior to Roe v. Wade, so we can make sure the pro-life movement didn't slip their own definition into the book.

[pravnik]

I recall my physical anthropology professor telling us that during times of famine, a fetus will leach nutrients from the mother to the mothers detriment, even the calcium from her bones. Maybe not technically parasitic, but at least reminiscent.

[Ropera]

from the 13th anniversary of his/her birth until he/she leaves home :p

Now seriously, as many pointed out above pregnancy is part of the propagation of the species. However, in a set of multiple gestation, one fetus can parasite the other(s) by getting more blood supply than the rest, thus provoking problems that could range from low birth weight to death on the "parasited" fetus(es).

[kanicbird]

If a fetus is a parisite, wouldn't a breat feeding child also be a parasite?

[Roches]

Normally, symbiotic, commensal and parasitic relationships have to be between members of different species. If the relationship is between members of the same species, it's really a different category. Besides, since providing nutrients to one's offspring (whether before or after birth) is absolutely essential to survival for mammals. Since having a large number of offspring who survive is the single most important measure of fitness for a species, the mother/embryo or mother/fetus relationship is unquestionably a beneficial one.

It's true that the embryo/fetus depends on the mother for nutrition during gestation, but this isn't parasitic, since the embryo/fetus is not harming the mother; the relationship would be commensal or even symbiotic, if those labels were appropriate. The mother will generally increase her intake of food in order to provide for the baby. Her own nutritional needs will still be fulfilled (which may not be the case for a person hosting a parasite), and some of the extra food she eats will nourish the embryo/fetus. This is no different than breastfeeding or providing food to children.

In a broader sense, remember that in modern societies most people are not food producers in their own right, and don't obtain food from nature. Does that mean that non-farmers are parasites?

I don't think the 'different species' requirement is 'cheap'. Nearly every species has some sort of relationship between members of that species that might be classified as symbiotic, commensal or parasitic. For example, males of virtually all species (at least, those which reproduce sexually) depend on females to produce zygotes using their sperm; females of virtually all species depend on males to fertilize their ova. Young mammals depend on their parents. In some cases, organisms from different species have evolved symbiotic, commensal or parasitic relationships that increase the fitness of one or both species. Biologists who study these relationships are interested in the ways that one species depends on another; the ways that members of a species depend on other members of the same species is a different matter altogether.

[nicolangerek]

Roches I appreciate the lucid explanation, especially the elaboration that the term parasitic/commensal and symbiotic should be applied to different species. If possible could you explain the category it would fit when you state "If the relationship is between members of the same species, it's really a different category", especially because it is the crux of your explanation.