Diatoms: Epithemia sp. dividing

[Beatsy]

A diatom caught (then cleaned) just before it became two diatoms. Girdle (side) view. This one is roughly 65 microns long and dead (it was cleaned in acid). A manual stack shot in bright field using a 20x plan objective. Near 100% pixel-for-pixel crop.

To briefly explain what you're looking at. Diatom valves are comprised of two halves called frustules. They are made of opaline silica and fit together like a funny-shaped pillbox and it's lid. When it's time to multiply, two new frustules begin to grow back-to-back *inside* the existing valve (the two lighter frustules in the pic). The growing frustules interlock with the original frustules (darker ones in the pic) and push them apart, making two new valves that each comprise one newly grown and one pre-existing parent frustule. The new diatom containing the larger half of the original valve (the "lid" of the pillbox) will be the same size as the original valve. The one that grows into the smaller half will result in a smaller valve. With each generation the average size of valves in the population decreases. Eventually, individuals become too small to produce viable offspring like this (asexually) and switch to sexual reproduction instead. This involves releasing auxospores and growing a new full-sized valve from scratch - and stuff. Mind boggling, really...

[Ramos Kenneth D]

Not that I do not know what a diatom is, I just would not have known exactly what I was looking at had you not included that informative narrative. Excellent photo and write up, well done!

[Mickyfynn]

Not that I do not know what a diatom is, I just would not have known exactly what I was looking at had you not included that informative narrative. Excellent photo and write up, well done!

Diatoms are algae found in fresh and salt water and soil. They are classified as eukaryotes.
About 20% of the air we breathe is created by these organisms!....
l

[dy5]

Thanks for including all that information with the excellent photo!

[75RR]

Great catch! Like Ramos Kenneth D, I too was unsure what I was looking at.

The one that grows into the smaller half will result in a smaller valve. With each generation the average size of valves in the population decreases. Eventually, individuals become too small to produce viable offspring like this (asexually) and switch to sexual reproduction instead.

They do seem to avoid sex as long as possible ... almost as if they can't be bothered. Cup of tea anyone?

[Bob-O-Rama]

I always wondered how that was managed. Great photo an narrative. I didn't know the subsequent divisions yields smaller and smaller daughters, that's an interesting twist to their life cycle.

[75RR]

.
Here is a visual representation
.

[wowjl]

Great science popularization

I wonder, what will happen to the same size as before?

[Beatsy]

...I wonder, what will happen to the same size as before?

It will die. The average diatom lifespan is (very approximately) 6 days. Given good conditions (temp, light, pH, nutrients, etc.) a population will double every 24 hours - if there's room to do so. So if the smaller diatoms didn't "reboot" into new full-sized forms, the entire population would disappear in a couple of weeks. A bit like the white dot on old CRT-based TVs

[wowjl]

I see. This means that I can keep observing and see the whole life cycle.

I will try....

[Beatsy]

I see. This means that I can keep observing and see the whole life cycle.

I will try....

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You certainly can observe the full life cycle, but not for individuals locked under a cover slip. AFAIK, conditions there are not conducive to multiplication at all (probably too little silica available for one thing). Best bet is to create a culture in a jar and continually sample that over time to find forms at the different stages. More of a statistical sampling than direct observation of individuals.

[Lou Jost]

That's a fantastic image. How did you get the diatom pair to exactly stand on edge? That must have been hard.

[Beatsy]

That's a fantastic image. How did you get the diatom pair to exactly stand on edge? That must have been hard.

Thanks Lou. Pure chance and trivially easy in this case. It had simply settled that way in the strew!

But it's easy enough to place them with a manipulator too as static tends to hold them in place until the mountant is activated (by breathing on the arrangement to slightly wet it). Some awkward ones can tip over again when wetted, but it's easy enough to hold individuals steady with a needle while the mountant re-dries - which only takes a few seconds. Putting several on edge in the same mount can be frustrating though