The genus of marine planktonic organisms known as Pleurosigma is named so for its shape. Sigma is a latin root used in reference to the shape of the organism. It has also been related to the orbital movement of electrons around an internuclear axis, which is similar to the orbital movement the Pleurosigma diatom makes around one of its tips during movement.3,6 The genus employs a pulsating of the body to induce gliding movement as well as occasional circular rotations around one end of the organism to change course.

Animation of a diatom from the Pleurosigma genus, observed in movement on 11/3/2015.

Animation of a diatom from the Pleurosigma genus, observed in movement on 11/3/2015. © 2015 Oliver Hickenbottom.

Pleurosigma is a genus of diatom. The organisms within the genus generally take the shape of an elongated diamond, with regularly pulsating inner organelles. The genus has these traits in common with the genus Gyrosigma, which has been observed to be much simpler in build and inner structure than the topic genus, Pleurosigma. It was first mentioned in published literature by W. Smith in 1853, after he had discovered the organism in 1852. In the years after the discovery, there was some confusion in planktonic studies wherein Gyrosigma was often confused with Pleurosigma, but the differences between the two diatoms have become much more apparent now.1,4,7 However, there are sometimes unclear lines between the two genuses in planktonic research depending on the appearance of each individual species.

Organisms categorized within the genus Pleurosigma appear all over the world, regardless of location.  The genus is one of the larger groups of diatoms, containing hundred of different species and also making it very difficult to identify exact taxonomy of organisms. Pleurosigma angulatum was the first species of the genus publicly discovered and recorded, and is considered the ‘parent’ of the species as a result.1,3,4

The Pleurosigma diatom has no specific environment, and is common all over the world as drifting algae.

The Pleurosigma diatom has no specific environment, and is common all over the world as drifting algae.

Pleurosigma organisms reproduce asexually, through cell division. They are single-celled organisms that split themselves into parts in order to multiply. It breeds particularly well in bays, inlets and ports. This makes it extremely common near civilian life, though it appears in the open sea that is uninhabited by humans as well. Given that Pleurosigma is part of the most abundant phylum of algae, this makes it a large part of marine ecosystems, contributing essential oxygen levels as well as possible negativity if nutrients in the water could induce eutrophication.4,8

A pelagic, or ocean-floating, genus, Pleurosigma organisms generally either float on the tides, sink to lower levels on top of the salt layer or attach to marine organisms. They are often hunted by animal larvae as well as other marine microorganisms, commonly dinoflagellates. They feed on a photosynthetic diet, like most other forms of marine phytoplankton.1,2,3,4

In the last ten years, research into a naturally-occurring organic compound called a Terpenoid has led some researchers to believe the Pleurosigma genus may be related to these very important compounds. Terpenoids are derived from hydrocarbon isoprene, and these compounds are often incorporated into everyday items like turpentine, perfume, rubber and food flavoring. Sesterterpenoids are rare, advanced Terpenoids with a C25 skeleton. Diatoms of the Pleurosigma genus have been tested and theorized to be highly related to the buildup of these Sesterterpenoids in the biosphere. These compounds have been isolated from the carbon matter of Pleurosigma diatoms.8,9

Limited research has been done on the organisms of the genus Pleurosigma in comparison to the genus Gyrosigma. However, there is evidence that Pleurosigma is more to our society and way of living than just a generator of Oxygen (important, nonetheless). These small planktonic organisms may be highly related to unique compounds found in and on our earth, as well as in the very products we consume every day.

Symbolic Pleurosigma

pleurosigma symbol illlustDespite the tiny size of the Pleurosigma diatom, it and its sister species, Gyrosigma, these slowly spinning and gliding organisms have a big impact on our lives–they help create the air we breathe. It is ironic, then, that the sesterterpenoid compounds they create also are used to create turpentine and car tires, products that are created at the risk of Earth’s health. 

  1. Deboyd L. Smith, A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae, Second Edition, 50-70, 1977.
  2. Robert Perry, A Guide to the Marine Plankton of Southern California, 3rd edition, 3-6, 2003.
  3. C.H. von Quillfeldt, Identification of Some Easily Confused Common Diatom Species in Arctic Spring Blooms, Botanica Marina Vol. 44, 378-385, 2001.
  4. Van Guelpen, L., G. Pohle, E. Vanden Berghe, and M.J. Costello. Marine Species Registers for the North Atlantic Ocean. 2005.
  5. F. A. S. Sterrenburg, Studies on the Genera Gyrosigma and Pleurosigma (Bacillariophyceae). The Typus Generis of Pleurosigma, some Presumed Varieties and Imitative Species, Botanica Marina 34:6, 561-574, 2009.
  6. F. A. S. Sterrenburg, Studies on the Genera Gyrosigma and Pleurosigma (Bacillariophyceae), Proceedings of The Academy of Natural Sciences of Philadelphia: 148, 165-169, 1997.
  7. Simon T. Belt, Important sedimentary sesterterpenoids from the diatom Pleurosigma intermedium, Chemical Communications 6, 501-502, 2000.

© 2015 Oliver Hickenbottom