In todays post, we will be taking a look at a very interesting and, in my opinion, a very beautiful diatom. This is special because I composed a stack of five different pictures at various angles to complete a composite of Actinocyclus normanii.
At a glance, the Genus Actinocyclus has some features that may only be visible with an SEM. Now here is an interesting fact: Actinocyclus normanii, may be considered invasive, which I never knew! This species in considered to be very cosmopolitan, being found in coastal, brackish, and planktonic environments.
Let us discuss some of the features that characterize this particular organism.
- Areolae radiate in pseudosectors
- Areolae similar in size across valve
- Rimoportulae marginal
Valves concentrically undulate, with radiate areolae. Areolae are 8-12 in 10 µm and maintain constant size throughout the valve. Rimoportulae (4-8) are located equally spaced along valve margins. The pseudonodule is not visible due to its position on the valve/mantle interface.
Now, there can’t be a diatom name that doesn’t cause confusion, due to the ever-ending process of name changing. From the good folks over at Algaebase, comes the narrative of the confusion. ” A freshwater species A. normanii has been recorded under various names during the last century (see Hasle, 1977) and caused much confusion. Hasle has shown clearly that it is truly an Actinocyclus. It is one of several basically marine algae which are becoming established in freshwaters, probably due to increasing eutrophication.”
First discovered and published as Coscinodiscus normanii in 1859 and inevitably changed names, the original picture shows a very good interpretation of how the areolae form radiating radicals. Compare that picture to the one below, and the similarities are uncanny. The stacked image of 6 individual pictures from different orientations ultimately show the complexity of the organism.
Science Thursday 