Diatoms By Stephanie La Vecchio Are you a

Diatoms By: Stephanie La Vecchio

Are you a diatom? l l l l Diatomae, also known as Diatoms’ are unicellular eukaryotes. For the most part, Diatoms’ are photosynthetic micro-organisms, although some may live heterotrophically. All Diatoms’ are enclosed by a frustule, siliceous skeleton that is made up of two values fitted together by a connective zone called a girdle. They are found in almost every aquatic environment including fresh and marine waters, soils in fact almost anywhere moist. They are non-motile, or capable of only limited mobility along a substrate by secretion of mucilaginous material along a slit-like groove or channel called a raphe. Being autotrophic they are restricted to the photic zone, water depths down about 200 m deep. Diatoms are commonly between 20 -200 microns in diameter, although sometimes they can be up to 2 millimeters long.

Sexually or Asexually or both? l l Diatoms can reproduce in two different modes, sexual and asexual. But, Diatoms have also been known to be both male and female. The temperature of the water, where the Diatom is located, and other such things can affect the gender of this organism. Diatoms have a unique “shrinking division” mode of asexual reproduction. After cell division, the two valves of the test separate. Each forms the epivalve of a daughter cell, and new hypovalves are secreted within each of the parent valves. The result is one cell that is the same size as the parent cell, and one cell that is slightly smaller. Due to the rigidity of the test material, growth of the cell is impossible once the test is secreted. Thus, the average diatom size gets progressively smaller with each round of replication. Very small diatoms may switch to a sexual mode of reproduction. The sexual reproduction mode allows for growth of the zygote to relatively large size.

Where are you hiding… l l l Diatoms can be found in both fresh water and marine environments. Generally, Diatoms inhabit most bodies of water in all parts of the world, if provided with sufficient amount of nutrients. In fresh water habitats, diatoms prosper throughout the year, especially in the spring and fall months. Not only do diatoms exist in streams, lakes and other bodies of water, but they can be found on the rocks, plants, and mud that are present within or at the border of water. In marine environments, diatoms have the capacity to exist within animals’ digestive tracts, in their shells, on macroalgae, or even on ice floats! The currents can serve as a method of moving organisms to new habitats. The Gulf Stream, for example has the capacity to move organisms from the East Indies up the eastern coast of the Unites States. Since diatoms can also become attached to the legs of insects and birds, as well as the scales of fish and the sides of ships, they are able to travel far and wide in order to inhabit new places. Diatoms can be found in the littoral, the ranges

What does a Diatom look like? l l l Individually, Diatoms do not tend to have strong, highly visible color. Though when diatoms are visualized in groups, there is a yellow tint that can be seen due to the presence of photosynthetic plastids. When observed as larger masses, the color takes on a darker color, often deep brown or black. Some diatoms also have a blue or green color, but these are the exception. l The size of these diverse micro-organisms varies greatly, spanning l a large range of values. Diatoms can form small colonies, and filaments have been seen to measure over two feet.