largest cell on Earth?

Pflieger Jean-Francois pfliegej at ERE.UMontreal.CA
Wed Feb 19 09:31:55 EST 1997


thedoms at mindspring.com (Marco Domeniconi) writes:
>lance at neuro.pharmacology.ubc.ca (Lance Corey) wrote:
>>brians at interlog.com (Brian Scott) wrote:
>>>Andrew Doherty  <A.Doherty at Bris.ac.uk> wrote:
>>>>> >long. Is the ostrich's egg really a single cell?!
>>>>> >
>>>>> Sure it is...isn't it?  I mean, it's an ovum and if it's fertilized
>>>>> it starts dividing right?  Help me out here people!  :-)
>>>>> 
>>>>Well, I'm not so sure an ostrich egg, as such, is a single cell. Surely
>>>>the ostrich ovem is the cell, which becomes the egg i.e. produces the
>>>>shell, yolk sac, albumin...etc. So the ostrich egg may only contain one
>>>>cell, but is not itself that cell - I think - sort of - d'ya get what I
>>>>mean? I'm not sure I do, but then I'm not an ostrich biologist!!!
>>>
>>>According to _Molecular Biolog of the Cell_ by Alberts et al.,  bird's 
>>>eggs are single cells.  
>>
>>IMHO, I don't blieve that the whole egg is one cell; more likely, it is a
>>cell surrounded by yolk and albumen.
>>
>According to my Cell Bio text (Alberts, etc. 3rd ed) an egg is defined
>as an highly specialized cell, containing stock piles of all materials
>needed for initial development of the embryo.  It is noted that
>mammalian eggs do not need to as large as birds or frogs because the
>embryo can take up nutrients from the mother.

>I do not think it is correct to state that the ostrich egg is not a
>single, large cell based on its high contents of nutrients reserves
>and fats (up to 95%). If such param for the identification of a "true"
>single cell was correct, then it would also exclude our own adipose
>cells, among the largest in our bodies.

>I do not have any ref to confirm the ostrich egg, but I recall having
>read somewhere that it is indeed the largest cell.

If you consider that spermatozoids (postmeiotic "cells") are true cells, 
you could consider that unfertilized ostrich eggs are cells. Fertilized 
eggs are "cells" (because dividing rapidly).

I think that postmeiotic structures (ova and spermatozoids) could not be 
considered as "cells" by comparison with somatic cells, for a given species. 
But it's a personal point of view.

If I remember well, there is an alguae which is visible without 
microscopic intrument (ressembling as a small "flower"), but has only one 
cytoplasmic compartment and one nucleus... a good large cell no? :-)

			Jean-Francois

-- 
Jean-Francois Pflieger		      "DINANZI A ME NON FUR COSE CREATE,
Universite de Montreal		       SE NON ETERNE ED IO ETERNA DURO:
Sciences Neurologiques		       LASCIATE OGNI SPERANZA, VOI CH'ENTRATE"
pfliegej at alize.ere.umontreal.ca	      (Dante, "l'Enfer, Chant III, vers 7 a 9)



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