Case of the Dancing Dinoflagellate: A Micro-murder…


It all started when I was innocently making videomicrographs of Cyanobacteria at 1,000X magnification. That is when I witnessed the lightening attack…! It was a dark and rainy day.

But I am getting ahead of the story…

I had a sample of Cyanobacteria from pond OS1 in the San Francisco Bay Heron’s Head Park salt marsh. It had been sitting for awhile in the sunlight of my office window.

HH-OS1-Cyanobacteria-huddled 003

Notice that the Cyanobacterial Filaments had all huddled into a bundle in one corner of the container. This always happens when the sample contains no mud or sand. Something about the smooth plastic of the container causes the Cyanobacteria to gather, rather than to spread out. Sand or mud in the sample results in a uniform bottom mat forming over the mud, and even sending filaments up the walls.

This tells us that Cyanobacteria can “sense” their environment, perhaps by sending out, exchanging, and receiving chemical signals. The “ball-like huddle” is probably the result of signals that, in a salt marsh pond, result in a uniform Cyanobacterial mat over the muddy bottom of the pond. Increasingly, microbiologists are recognizing that bacteria send and receive chemical signals. Years ago, my friend Ken Nealson studied bioluminescent marine bacteria. He found that solitary bacteria, or even dilute suspensions of these bacteria did not glow. When the population reached a certain density, however, the luminescent apparatus was turned on – creating “sea glow”. This is an example of “quorum sensing”, where the concentration of a signal chemical being exchanged triggers group behavior.

You can see that this is really a “ball” of Cyanobacteria huddling near the wall of the container by looking at it from the side.

HH-OS1 Cyanobacteria-huddled 009

I placed about 100-microliters drawn from just above the top of the mound on a slide. This picked up a few filaments and, as expected, a few of the other critters that live with the Cyanobacteria. Cyanobacterial Filaments are one of the community-defining organisms of the salt marsh ponds and support a micro-community of many other organisms, from Diatoms and Ciliates to the larvae of insects and marine invertebrates.

Here is an earlier photomicrograph, taken at 1,000x magnification and 3x zoom, of a Cyanobacterial Filament. The arch is the filament. Notice that is is made of many “layers”, one after another along its length. The round disk on the upper left is a single Cyanobacterium [or, Cyanobacterial “cell”]. The “bullet-shaped” filament on the lower left is the end of another Cyanobacterial Filament.


I was after a videomicrograph of a moving Cyanobacterial Filament, using the Olympus microscope at 1,000x magnification. I wanted to use Hoffman Modulation Contrast optics to enhance the detail and contrast. The camera was the Nikon Coolpix 885 set at 3x zoom.

I got several videos of Cyanobacterial Filaments motoring along by themselves, but the most interesting shots included an Algal strand. You can see the algal strand next to the moving Cyanobacterial Filament in the videomicrograph at the beginning of this post. Notice that the algal strand is not moving and the Cyanobacterial Filament is.

The alga is multicellular and about the same size as the Cyanobacterial filament. Here it is in more detail:

Algae HH-1000xHMC-182

You can see the wall of the algal filament, the individual cells, and the chloroplasts inside the cells. Fossils of algae are found in rocks as old as 1.5-billion years. Algae are Eukaryotes, having true cells and nuclei with a nuclear membrane. The chloroplasts inside the algal cells have their own DNA, and it is thought that they originated as Cyanobacteria that entered into a symbiotic relationship with a non-photosynthetic cell.

Following the algal strand along, I came upon three cells of the colonial Diatom Melosira sandwiched between the algal strand and a Cyanobacterial filament.

Algae-Cyanobact-Melosira HH-1000xHMC-195

The Diatoms evolved much more recently, slightly before or around the time of the mammals. Melosira is a “centric” diatom, rather like a Petri dish in structure. You can see that more clearly in the next photomicrograph:

Algae-Diatoms HH-1000xHMC-169

Following the Cyanobacterial Filament, we see it here moving along by itself, having left the Algal strand behind.

Continuing further along the Cyanobacterial Filament, I came upon a Dinoflagellate hovering above it.

Dinoflagellate Over Cyanobacteria 1000xHMC 220

It is not unusual to see various microorganisms clustered around Cyanobacteria. Cyanobacteria are photosynthetic and release oxygen. Indeed, the action of Cyanobacteria like this one, over the last 3-billion years, produced the oxygen we breath. Usually the microorganisms around Cyanobacteria are small ciliates and aerobic bacteria. Sometimes the Cyanobacteria appear hairy from the clusters of fine rod-like bacteria.

I am not sure why the dinoflagellate hovered over the Cyanobacterial strand, but suddenly it went into a sort of dance…

When it came to rest, I noticed an ominous critter moving slowly downward toward it.

Moments before the attack 223

It was a large Ciliate, drawn not by oxygen, but by the prospect of lunch. The attack was sudden.

As quickly as that, the lovely red Dinoflagellate was gone. It was on its way to becoming “Ciliate”, along with several other Dinoflagellates that had been playing around the Cyanobacterial Filament.

Dinoflagellate becomes Ciliate 227

Especially for microorganisms, life has its ups and downs.

One Response to “Case of the Dancing Dinoflagellate: A Micro-murder…”

  1. Mike Barlow Says:

    The last video might be a good candidate for musical background… Again, thanks for posting these.