Bacillaria paxillifer - Is Not a Caterpilififer - Video

Mitch640 · Post by **Mitch640** » Thu Oct 04, 2012 12:33 pm

This has got to be one of the weirdest lifestyles around. It's common name is Carpenters Rule Diatom. A bunch of individual diatoms form a commune to.... Do what? What is the real purpose for a species to do this? Or is there even a purpose? Another mystery of the small world.

http://youtu.be/klMGTnqMwfg

curt0909 · Post by **curt0909** » Thu Oct 04, 2012 1:12 pm

One possible advantage would be locomotion. As a group they are more mobile than as individuals. I'm curious if they are the result of individual diatoms finding each other and attaching themselves or if they form their attachment on division(reproduction). I would lean towards the latter since it seems like the easier option.

Mitch640 · Post by **Mitch640** » Thu Oct 04, 2012 1:55 pm

Hi Curt. I kind of got that they are a species, and I assume, their behavior is programmed into their DNA. They get too many members, they break off and start another chain.

Maybe this activity is a way to spread the spores so to speak. There did seem to be a lot of them. I was only able to find one other video when searching and it only had 5 or 6 individuals, but was still doing the active movement thing.

And sorry for the poor quality, but he was in all that junk and rather than clip the not so good spots, I left them in in the interest of science. Even if it wasn't in focus all the time, at least you could see what it was doing.

Rylee Isitt · Post by **Rylee Isitt** » Thu Oct 04, 2012 2:41 pm

Colonial behaviour often offers benefits in terms of safety and division of labor.

Sponges, for example, are one of those organisms that blur the lines between a colony of a micro-organisms and a true multicellular animal. A sponge is an assemblage of cells, with each closely resembling a free-living micro-organism (eg, the collar cells are rather like solitary choanoflagellates), but these individual organisms benefit from living together. Eventually, they co-evolve for so long that they become dependent on the specialized services offered - individual cells cannot do everything needed to survive.

Your specimens here might just be on the very beginnings of this kind of colonial to multi-cellular organization - still having everything they need to survive alone, but benefiting in some way from grouping up.

Mitch640 · Post by **Mitch640** » Thu Oct 04, 2012 3:03 pm

Thanks Rylee, that sounds logical. Did you see the "cilia" on the bodies of the diatoms? What do you think those are?

Rylee Isitt · Post by **Rylee Isitt** » Thu Oct 04, 2012 9:47 pm

Possibly flagellae - used for moving around.

I did a bit of Googling and curt0909 seems to have hit the mark with the comment that the colonial nature aids locomotion. Apparently, they can move very quickly as a result. I imagine they can use this ability to quickly migrate up/down the water column.

Mitch640 · Post by **Mitch640** » Fri Oct 05, 2012 3:57 am

When I found them, they were at the top of the sediment in a gallon jar. sitting in my window with full sunlight. But I can see in nature where they would want to get near the light. They seem to be full of chloroplasts.

Bruce Taylor · Post by **Bruce Taylor** » Fri Oct 05, 2012 4:11 am

Rylee Isitt wrote:Possibly flagellae - used for moving around.

Pennate diatoms do not have motile flagella, or cilia. Many have fixed setae, but I don't know if Bacillaria has these (I'm on a small laptop, and couldn't see the structures Mitch describes).

Mitch640 · Post by **Mitch640** » Fri Oct 05, 2012 4:26 am

Bruce, what I saw as cilia or flagella, were more like "bristles". They did not move in themselves, but they stood straight out from the body and most of the individuals did seem to have them. They are more visible in frames very near the end of the video and you should be able to see them at 720p and full screen, maybe even on the laptop.

I'll see if I can get a frame grab of them.

René · Post by **René** » Fri Oct 05, 2012 8:25 am

The 'bristles' (I haven't seen them in the movie) most likely are attached bacteria, very common if you start growing things yourself. Bacillaria moves just like a lot of pennates do: they secrete polysaccharides through the raphe slit, laying down a track, and then move up and down this track with motor proteines. In this case however, the cells slide alongside eachothers raphe. They are not planktonic, live on the (mud) surface and can indeed very quickly move to another place. How these tiny cells coordinate their gliding movement in one direction at the time (which generally they seem to do) is an interesting question to solve. Can't come up with a way to study this mechanism, it's worth a couple of PhD's if not a professorship.

Best wishes, René

Mitch640 · Post by **Mitch640** » Fri Oct 05, 2012 8:49 am

Thanks Rene. Being a rank amateur, I saw the "bristles", called them cilia and generally did not know what they really were. It did cross my mind that they were indeed some form of hitchhiker growing on the shells of the individuals, but couldn't find a way to rationalize them not being scraped off in the violent movement of the organism against the sand particles. He certainly wasn't taking care to be easy on them. LOL. The bristles certainly do behave like other organisms I have seen attached to the shells of cyclops though, along with the other dustbunnies.

<edit> With all the junk attached to his shells, it would seem that he is not a new kid on the block and has been around for awhile.

Rylee Isitt · Post by **Rylee Isitt** » Fri Oct 05, 2012 9:12 am

René,

Thanks for that great info!

What is their worldwide distribution? I wonder if it's possible for me to find some of these in our local shallow lake, or any of the nearby wetlands...

It's a shame we can't (yet) watch a living organism under a scope that gives you resolution fine enough to see the structure of small molecules, a field of view wide enough to see a whole organism, and frame rate high enough to slow down the process of metabolic pathways. If I had to guess, we won't be able to do that any time soon, either.

I guess you could look at protein structure and try to infer their purpose. Knock out or inhibit the coding DNA or mRNA for suspect proteins and see if this breaks the coordination, and that way you can (slowly) identify the protein components involved. Maybe you can grow diatoms in different jars treated with microRNA that degrades the specific mRNA sequences you want to target.

But you'd still be left with having to figure out how the pieces interact, and recognize that non-protein messenger molecules may be involved. Plus, the movement is directional, so there are likely two different pathways here.