Trachelomonas Euglenoid Under The Microscope

Trachelomonas is a genus of swimming, free-living euglenoids characterized by the presence of a shell-like covering called a lorica. Details of lorica structure determine the classification of distinct species in the genus. The lorica can exist in spherical, elliptical, cylindrical, and pyriform (pear-shaped) forms. The lorica surface can be smooth, punctuate or striate and range from hyaline, to yellow, or brown. These colors are due to the accumulation of ferric hydroxide and manganic oxide deposited with the mucilage and minerals that comprise the lorica. In Trachelomonas, the presence of a lorica obscures cytoplasmic details of the underlying cell. In each Trachelomonas cell, there is a gap at the apex of the lorica from which the flagellum protrudes. Thickening around this gap results in a rim-like or collar-like appearance. During asexual reproduction, the nucleus divides yielding two daughter cells one of which exits through the opening in the lorica. This new cell then synthesizes its own new lorica.

Trachelomonads are free-swimming, solitary, photosynthetic flagellates ranging in size from 5-100um, with an ovoid shape, sharing similar morphological characteristics with its sister group, Strombomonas These cells are enclosed in a rigid, shell-like envelope, made up of minerals and polysaccharide mucilage, with a defined collar or truncate extension that surrounds an anterior apical pore where the flagellum emerges from, also known as a lorica. The lorica can be distinguished between different species by the orientation of spines or other ornamentations, such as pores, warts or ridges, and can range from being colourless to orange/brown or even black based on the nutrients in their surroundings. Most species are phototrophic, having a characteristic green colour due to the discoid or flattened, shield-like chloroplast, which usually bears sheathed, projecting or naked pyrenoids. The few species that are osmotrophic, lack chloroplasts; therefore, they are colourless. Similar to other euglenoids, the cell has many paramylon bodies that are used for the storage of starch; these can be a distinguishing trait for species with similar lorica structures. The structure and ornamentation of the lorica is very dependent on the growth conditions, especially the availability of nutrients. Therefore, the size, shape, collar form and the presence of spines and pores can vary, showing morphological plasticity within species. This can make it difficult to describe species since morphological features can vary greatly. Trachelomonads also have an eyespot, a feature of photosynthetic euglenoids, located outside the chloroplast with orange to red pigmentation. These cells also have one long emergent flagellum that has previously been identified to emerge from the apical pore, and a shorter flagellum that is within the furrow and not used for motility. Under light microscopy, it is also possible to see condensed chromosomes.

[Microscopy]

A very good and informative video! I know that it is very difficult to make good footage of these algae due to their form and movement. Good work!

[bitbitk]

Thank you so much, I was trying to identify these ‘little orange balls’ for SO long and this video with their movement helped me be sure of it.