Cytoplasmic streaming in as single Spirogyra cell
This is a single green alga cell, from the genus Spirogyra. Spirogyra gets its name because inside each cell is a ribbon-like green chloroplast that coils and gives the cell its spiral appearance. Cells are filled with cytoplasm–a clear water-based fluid packed with proteins, nutrients and vesicles–that constantly circulated in the cell to keep all its contents moving and distributed around the entire space. In a big algal cell like this one you can see cytoplasmic streaming in action.
Chloroplast rotation in Mougeotia sp.
The filamentous green alga Mougeotia has broad flat chloroplasts. Broad and flat is good for harvesting energy from sunlight, like a solar panel, but sometimes light can be too bright and that can be bad for those big flat chloroplasts.This is because when chloroplasts are exposed to too much light it can lead to damage and degradation of some of the proteins contained in the chloroplast. You really can have too much of a good thing. To prevent this damage the chloroplasts in Mougeotia are able to pivot and in this video, you can see the chloroplasts doing just that. In this time-lapse video (that covers about six minutes in real time) you can watch the green chloroplasts pivot around in the cell and change from being broad, flat side on, to an edge-on orientation. In this new edge-on position only the thin edge of the chloroplasts is exposed to the light and thus the damage caused by overexposure to light is reduced. Such clever little chloroplasts.
Phagocytosis - Collodictyon triciliatum
A single cellular predator, Collodictyon tricilatum seeks out and eats two green algae cells. Yum. This video is sped up six times, total process takes roughly six minutes.
Phagocytosis - An amoeba from the salt marsh in Brooklyn.
This little character is an amoeba. It's shaped like a blob. Amoebas are predators, they need to eat to survive. In this clip, you can see it trying to eat a long alga. The alga is far too long to fit inside the amoeba, and sure enough (after a thorough investigation) the amoeba gives up on its lunch. This clip is sped up four times, so covers about four minutes in real-time. Amoebas are slow.
Motility - Gilding motion in a pennate diatom
This is a pennate diatom from genus Gyrosigma. Many species of pennate diatom are able to glide. They glide by excreting a mucus out the bottom of their cell, which gives them a nice slick surface to move over.
Prey capture and phagocytosis - Histiobalantium ciliate
This ciliate is covered in tiny hair-like structures called cilia. Those cilia are extremely sensitive and allow the ciliate to sense movement in the water nearby. It can sense when prey is near, and spin itself around at breakneck speed to snatch up any small unlucky cells that get too close. The ciliate has an "oral cavity" in its cell that acts like a mouth. It holds the prey in this cavity by covering it over with a flap of its cell membrane. Once it has the prey trapped it phagocytoses it, engulphing it in a digestive vacuole inside itself. The ciliate will pump acids and digestive enzymes into that vacuole, slowly digesting the little cell inside.
Colony gliding motility - Bacillaria diatoms
Many pennate diatoms are capable of gliding motility, but Bacillaria diatoms take it to the next level by leveraging that gliding motility while in colony formation. The colony is made up of many individual cells. Each cell is long and narrow and is attached to its neighbors along the long edges of the cell. When they glide they push or pull against each other, allowing the colony to extend and contract to move about in a step-wise manner. By working together like this the colony can move much quicker than just a single diatom alone.