A Desmid’s Mossy Home

What am I looking at?

This is a desmid (an alga in the order Desmidiales) sitting on top of a moss leaf (Cinclidium stygium). The desmid is cylindrical and green with purple and orange outlines (1). The moss leaf is the lattice structure behind the desmid (2). You can see the individual cells of the leaf outlined in orange and purple (3). You can also see the chloroplasts within some of these plant cells in green (4).

Click on the right arrow to see another desmid on a moss leaf.

Biology in the background

Desmids are green algae that come in many different shapes and sizes, but they all have one thing in common – they are made of symmetrical halves called semicells. At first glance, the two halves seem to be mirror images of each other, but in fact, one of them is rotated by 180 degrees. This makes them incredibly fascinating to look at, almost like living snowflakes. You can find them in water that is fairly acidic and with a low mineral and nitrogen content, like ponds, swamps, or bogs.

Moss is a type of plant that can grow on land or underwater. They are nonvascular plants, which means they don’t have “veins” that carry water and nutrients like trees and many flowering plants do. Many mosses have leaves that are often only one cell layer thick, making them hard to see with the naked eye but fascinating to look at under a microscope.

Desmids range from 40 micrometers to 300 micrometers long, or roughly half to four times the width of a human hair. Moss often grows low to the ground and does not normally exceed a height of 10 centimeters, or roughly five times the width of a human thumbnail. However, there are mosses that can be 50 centimeters tall, or roughly 20 inches high.

Technique

These images were created using a form of light microscopy known as polarized light microscopy.