Size of individual cells?

This thread reminded me of an old question: Are the individual cells which make up various creatures approximately the same size?

I’m thinking specifically of cells which make up multi-cellular animals, I’m aware that single-celled creatures vary greatly in size. And I realized that specialization of a cell will incease or decrease size of that type.

But as huge as the dinosaurs were, would their individual cells have been larger? Would an elephant’s muscle or retinal cells any larger than those of a mouse?

Cell size doesn’t necessarily scale with animal size. You’ll see a larger variation from cell specialization.

For a truly remarkable example, look at a giant squid axon. Those can get up to a millimeter in diameter and are visible to the naked eye. By contrast, human axons are only a few microns.

generally, a cell’s nucleus size is determined (very roughly!!) by the size of the DNA of the animal. Dinosaurs had huge long DNA, so their nucleus sizes were considerably larger. Large cells need large nuclei, for effective mRNA transport (because they have a larger surface area and more pores) and for faster protein assembly in the cytoplasm.
Also, by straight-up observation you can clearly see the bone-cells in a dinosaur’s fossils are a lot larger than in other animals.
This is thought to be one of the ‘reasons’ junk DNA exists, to pad-out cells and ensure correct nucleus size.

From this you can extrapolate that larger animals with longer DNA (which is normally true) will have larger cell sizes, but there are huge variances and you can’t make a perfectly reliable conclusion based on this

It’s a complicated question, and the answer is “yes and no.”

Some cells in certain animals (notably neurons,) are going to be MUCH bigger. Giraffes and giant squid have neurons that are a few meters long. Even humans have neurons over a meter long. Compare this to a small rodent or bird, who’s largest neuron might be less than a centimeter.

Can I have a citation for this? To the best of my knowledge, no one has yet isolated any dinosaur DNA at all. There have been a few claims, which haven’t panned out, yet even those that made those claims were only claiming to have isolated a few hundred nucleotides at best.

To the OP: there’s a fair bit of variability in cell size. Probably the most dramatic is that between prokaryotic (bacterial) cells and eukaryotic (everything else) cells. This site is useful for visualizing relative sizes.

That is actually squid giant axon, i.e., the giant axon that is found in a regular squid, not a regular axon from a giant squid; which actually makes its size all the more impressive. (I don’t know if giant squid have giant squid giant axons, but if they do they are probably not much thicker than regular giant squid axons, just longer.)

Of course, when it comes to colossal squid, all bets are off!

They haven’t actually found the DNA, but they have looked at the cell sizes, from which they know the properties of the nucleus, from which they can get that they had large DNA to fit into the nucleus, there a number of articles on this on the internet but they all reference thispaper

Xenophyophorea is a deep-sea phylum of amoeboids (a branch of eukaryotes containing not just little protozoa but also slime molds etc. and the shelled foraminifera, to which the xenophyophores are probably closest) in which each organism is single-celled, and yet can be a few feet in diameter.

I’ve seen pictures of an amoeba engulfing an arthropod of some sort. Clearly, that arthropod has teeny tiny cells.

An unfertilized chicken egg is a single cell, and it’s clearly a much bigger cell than even the largest cell in a human body. Cells can vary enormously in size.

I’ve read in the past that bird cells are smaller than the cells of other animals; the hypothesis as to why is that it’s an adaption for flight. Smaller cells allow for more relative surface area for each cell, and a higher metabolic rate.

There is a single cell INSIDE a chicken egg. Most of the egg is no part of the cell.

I’ll admit to being surprised eltro102 did turn out to have a citation for that. :slight_smile:

My confusion stemmed from the current understanding that birds are dinosaurs, so we could in theory look at bird nuclei to answer questions about dino nuclei.

However, the abstract from the paper is pretty confusing to me:

Aside from the usual confusion caused by the apparent fact that birds do not come from the ornithischian (“bird-hipped”) dinosaurs, what baffles me is the idea that the bone cells in the saurischian dinosaurs were supposedly unusually small; those animals included the largest land animals ever known. I’m also shocked to see that the differences between the saurischian and ornithischian lines go all the way down to the cellular level; that seems like too fundamental a thing to vary among lineages so similar and so related.