Desmids - Beautiful single celled algae

There are many different types of algae, differing in both size, shape, color, habitat and more. Some types are multicellular and very large like seaweed, some are microscopic and colonial like Eudorina, while others consist of only a single cell. Some of these are called desmids (desmidiales).

Desmids are highly symmetrical unicellular green algae which can take on many different shapes depending on the specific species. The desmids also vary in size between species, the smallest being only a couple of microns and the largest reaching a size of several hundreds of microns and are visible with the naked eye. Desmids are most commonly found in freshwater where several thousand species can be found.

Desmids are made up of two identical semi-cells connected by a thin bridge called an isthmus. This is where the nucleus is located, which holds the cellular DNA. When the cell divides each semi-cell will grow a new mirror semi-cell leaving two full cells. Inside the cell is a single large green chloroplast where photosynthesis occurs. This produces energy for the cell, but if the energy is not needed right away, small round structures called pyrenoids form carbohydrates to store the energy for later use. These pyrenoids are especially visible in the desmid micrasterias rotata seen in the images above and below.

Note the clearly visible round pyrenoid structures inside the cell.