# Is an egg a big cell? **URL:** \ **Category:** Factual Questions\ **Created:** [November 16, 2006, 11:39am UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658 "2006-11-16T11:39:04Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Gerome](https://avatars.discourse-cdn.com/v4/letter/g/85e7bf/32.png) [@Gerome](https://boards.straightdope.com/u/Gerome)\ **Post date:** [November 16, 2006, 11:39am UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/1 "2006-11-16T11:39:04Z")
I realise that mammalian eggs (such as are produced in the ovaries) are single cells. Is this also true for reptiles, birds, fish etc that lay eggs outside the body? When I buy half a dozen hen eggs in a cardboard carton, am I in fact buying six individual cells? This question has always bugged me. ---
**Author:** ![Crotalus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crotalus/32/41_2.png) [@Crotalus](https://boards.straightdope.com/u/Crotalus)\ **Post date:** [November 16, 2006, 12:41pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/2 "2006-11-16T12:41:58Z")
Poultry eggs are a collection of many, many cells. ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [November 16, 2006, 12:44pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/3 "2006-11-16T12:44:23Z")
Eh, no, **Crotalus**. Eggs are one big cell, yes. Even ostrich eggs. ---
**Author:** ![Crotalus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crotalus/32/41_2.png) [@Crotalus](https://boards.straightdope.com/u/Crotalus)\ **Post date:** [November 16, 2006, 1:18pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/4 "2006-11-16T13:18:04Z")
Oops. Sorry. That’s what I get for thinking I know something. ---
**Author:** ![Crotalus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crotalus/32/41_2.png) [@Crotalus](https://boards.straightdope.com/u/Crotalus)\ **Post date:** [November 16, 2006, 1:28pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/5 "2006-11-16T13:28:40Z")
Some confirmation of what **Nava** said [here](http://www.newton.dep.anl.gov/askasci/mole00/mole00128.htm) . ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [November 16, 2006, 1:55pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/6 "2006-11-16T13:55:38Z")
[QUOTE=Crotalus] Some confirmation of what **Nava** said [here](http://www.newton.dep.anl.gov/askasci/mole00/mole00128.htm) . [/QUOTE] From the link: > [@](#): > > It so happens that with or without the yolk and albumen, the poultry ovum is the largest living cell. Several months ago someone asked about single-cell seaweed. I posted to the thread because I’d recently read a paragraph in _Calypso Log_ about _Caulerpa taxifolia_ that made the claim, and I found the statement to be unbelievable. (I thought perhaps they had misspoke or worded the claim poorly.) I was amazed it’s true. [From here](http://www.uow.edu.au/science/biol/staff/adavis/caulerpa.html) (emphasis mine): > [@](#): > > _Caulerpa taxifolia_… possesses an unusual cell structure — a non-compartmentalised multinucleate organisation where a single connected thallus that can be **several metres long** is akin to a single cell. Wouldn’t that take the crown from poultry ova as the ‘largest living cell’? ---
**Author:** ![athelas](https://avatars.discourse-cdn.com/v4/letter/a/5e9695/32.png) [@athelas](https://boards.straightdope.com/u/athelas)\ **Post date:** [November 16, 2006, 2:48pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/7 "2006-11-16T14:48:18Z")
Well, it sort of depends on what you define as “cell”. Basically the organization is a bunch of cells with channels connecting all of their cytoplasm, so structurally it’s sort of a whole lot of cells, but it also has properties of one large cell. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 16, 2006, 2:53pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/8 "2006-11-16T14:53:15Z")
[QUOTE=Johnny L.A.] Caulerpa taxifolia… Wouldn’t that take the crown from poultry ova as the ‘largest living cell’? [/QUOTE] The alga is probably multinucleate; a mass of protoplasm containing thousands of nuclei, and their associated chromosomes. Such [coencytic](http://en.wikipedia.org/wiki/Coenocyte) structures more closely resemble [The Blob](http://www.imdb.com/title/tt0051418/) which tried to eat Steve McQueen than they do a normal cell. ---
**Author:** ![gigi](https://avatars.discourse-cdn.com/v4/letter/g/a587f6/32.png) [@gigi](https://boards.straightdope.com/u/gigi)\ **Post date:** [November 16, 2006, 3:01pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/9 "2006-11-16T15:01:24Z")
[QUOTE=Squink] Such [coencytic](http://en.wikipedia.org/wiki/Coenocyte) structures more closely resemble [The Blob](http://www.imdb.com/title/tt0051418/) which tried to eat Steve McQueen than they do a normal cell. [/QUOTE] Man, I love these boards. ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [November 16, 2006, 3:13pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/10 "2006-11-16T15:13:23Z")
Don’t forget the giant [space amoeba](http://en.wikipedia.org/wiki/The_Immunity_Syndrome_(TOS_episode)) from Star Trek. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 16, 2006, 3:43pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/11 "2006-11-16T15:43:00Z")
To elaborate, the yolk of an unfertilized egg is essentially a single cell. The cell is almost completely filled with food material, which is the yelllow substance of the yolk. On the surface of the yolk, there is a small _germinal disk_, which contains the cell’s cytoplasm, nucleus, and other organelles. Once fertilzed, this germinal disk divides and becomes a multicellular embryo, so a fertilized egg is no longer a single cell. The egg white (albumen), various membranes, and the shell are not part of the cell. The yolk + germinal disk of the ostrich is the largest extant cell with a single nucleus. Some extinct birds and dinosaurs had larger eggs. _Caulerpa_ is indeed a single cell with multiple nuclei. Since some species can get up to 3 meters long and have 200 fronds, they could potentially outweigh an ostrich egg cell. Some fungi, notably bread molds, have a similar coenocytic multinucleate. However, I am not aware that any of these get large enough to compete with avian eggs or _Caulerpa._ ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [November 16, 2006, 3:44pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/12 "2006-11-16T15:44:46Z")
The site linked to does not come clearly down on the side of “the egg is a giant cell.” It says that by some definitions, it is, and by some definitions, the egg simply contains a large cell surrounded by yolk, other stuff, and a shell. Its my understanding that the egg shell is evolutionarily cognate with the mamalian (now I can’t remember what it’s called) “bag” that surrounds an infant in the womb. -FrL- ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 16, 2006, 3:50pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/13 "2006-11-16T15:50:38Z")
[QUOTE=Colibri] Some fungi, notably bread molds, have a similar coenocytic multinucleate.\* [/QUOTE] coenocytic multinucleate **structure**. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 16, 2006, 4:02pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/14 "2006-11-16T16:02:22Z")
[QUOTE=Frylock] The site linked to does not come clearly down on the side of “the egg is a giant cell.” It says that by some definitions, it is, and by some definitions, the egg simply contains a large cell surrounded by yolk, other stuff, and a shell. [/quote] The answer given on that website is rather garbled, and I wouldn’t consider it at all authoritative. Since the yolk material and germinal disc are contained within a single cell membrane, by the usual definition they constitute a singel cell. > [@](#): > > Its my understanding that the egg shell is evolutionarily cognate with the mamalian (now I can’t remember what it’s called) “bag” that surrounds an infant in the womb. You are thinking of the amnion, but this is not homologous to the egg shell; birds’ eggs also have an amnion. [Here’s](http://www.ucmp.berkeley.edu/vertebrates/tetrapods/amniota.html) a diagram of a typical amniote egg. (Amniotes include reptiles in the traditional sense, birds, and mammals.) Various membranes associated with the embryo include the amnion, allantois, and chorion. These mainly originate from the original egg cell. The egg white (albumen) and the egg shell are not derived from the embryo, but are secreted by the mother. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [November 16, 2006, 6:37pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/15 "2006-11-16T18:37:02Z")
A mammalian egg is a single cell, but not a complete one. It has half a set of chromosomes, and it could never develop on its own. When it meets with a sperm, also a half cell, the fertilized zygote they form is one complete cell, not two. That complete cell is capable of developing into a blastosphere, then an embryo, then a fetus (I think I may have left out a step or three.) All that stuff will happen only if a series of conditions are just right. If they aren’t, the zygote gets sloughed off, and the female mammal is unaware that fertilization took place. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 16, 2006, 6:53pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/16 "2006-11-16T18:53:22Z")
[QUOTE=AskNott] A mammalian egg is a single cell, but not a complete one. It has half a set of chromosomes, and it could never develop on its own. [/QUOTE] I wouldn’t phrase it that way. A mammalian ovum is certainly a complete cell; it just has half the normal number of chromosomes. Most multicellular animals have paired chromosomes, that is, they are diploid. Gametes (ova and sperm), and some insects (notably male ants, bees, and wasps) have a single set of chromosomes, and are referred to as haploid. Many fungi and algae are also normally haploid. As shown by these organisms, haploids are perfectly capable of developing and functioning as organisms, and their cells can’t be considered to be “incomplete.” This is the source of the common joke that the “H” in Jesus H. Christ stands for “Haploid” (due to his virgin birth). ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [November 16, 2006, 8:24pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/17 "2006-11-16T20:24:53Z")
If an chicken egg is one cell, where’s all the chromosomes at? ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [November 16, 2006, 9:00pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/18 "2006-11-16T21:00:20Z")
[QUOTE=Inigo Montoya] If an chicken egg is one cell, where’s all the chromosomes at? [/QUOTE] If you crack an egg into a bowl, you’ll find a white spot on the yolk. That’s the germinal disk, and the chromosomes are inside it, along with 99% of the other organelles. ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [November 16, 2006, 9:03pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/19 "2006-11-16T21:03:39Z")
\*\* thinking \*\* Does roster sperm have to get through the shell and then find a needle in a haystack inside the egg? How’s that work? ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [November 16, 2006, 9:14pm UTC](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658/20 "2006-11-16T21:14:38Z")
[QUOTE=Inigo Montoya] \*\* thinking \*\* Does roster sperm have to get through the shell and then find a needle in a haystack inside the egg? How’s that work? [/QUOTE] Nope. The sperm is shared with the chicken before the eggs are shelled. Roosters don’t have penises. Rather, both roosters and hens have cloacas, which are usually internal tubes that carry waste. When chickens do the nasty, they evert (turn inside out and stick out of their bodies) their cloacas. The rooster cloaca has sperm on it, and he rubs it on the hen’s cloaca, which then retreats back into her body. Then the sperm fertilize the germinal disk inside her, before the shell is formed around the egg. Any hen has several eggs in varying stages of development inside her at once, and her body stores the sperm for a little bit to fertilize a bunch of eggs with it, not just one egg for one bout of sex. [Next page](https://boards.straightdope.com/t/is-an-egg-a-big-cell/380658.md?page=2)