Here we have a beautiful chlorophyte, Pediastrum duplex. The overall genus of Pediastrum has a large array of species associated with it, each with minor characteristics that allow them to be separated based on morphology and the inevitable genetic component. For instance, Pediastrum duplex is separated out from other species by having very large and conspicuous inter-cellular spaces, as clearly shown below in the picture.
In our master guide of references that we use on a daily basis, what makes one organism, lets say, species A as compared with species B, can be as minor as how small or large the individual cells of the organism is. If it happens to be outside of the size range, more than likely it doesn’t fit the characteristics of that species.
For example, in our reference, The Freshwater Algal Flora of the British Isles, Pediastrum duplex, has some of the following characteristics: Coenobia 35-135 (-212) micrometers across, with cells adjoining inter cellular spaces having concave side walls, and marginal cells 7-24 (-28)x 6-24 (-28) micrometers bearing short, cylindrical tapering truncate projections.
Here is a link to Algaebase, which is a database of information on algae that includes terrestrial, marine and freshwater organisms. This link is for the genus Pediastrum, which includes a general description in more detail, along with all species currently recognized.
Enjoy!!
Science Thursday 