Euglena acus - Nature's Tiny Dynamo

What is Euglena acus? Euglena acus is a species of the genus Euglena, belonging to the phylum Euglenophyta. It is a flagellated protist that can photosynthesize like a plant due to the presence of chloroplasts, but it can also move and ingest food like an animal. This dual mode of nutrition—photosynthesis and heterotrophy—makes it a unique and adaptable organism.

Habitat and Distribution In Northern Ireland, Euglena acus is predominantly found in freshwater environments such as ponds, lakes, and slow-moving rivers. These water bodies provide the ideal conditions for Euglena acus to thrive, with ample sunlight for photosynthesis and organic matter for heterotrophic feeding. The nutrient-rich waters of Northern Ireland’s wetlands and bogs also support healthy populations of Euglena acus.


This specific specimen was taken from a Sphagnum Moss sample from the peat bog pools at Brackagh Bog, Portadown, Co Armagh.

Euglena acus - photographed at 400x magnification under a microscope 

Physical Charcteristics:

Cell Structure: Euglena acus is a single-celled organism with a flexible and elongated spindle-shaped body. The cell is encased in a proteinaceous layer called a pellicle, which provides structural support while allowing flexibility and movement.


Flagellum: One of the most distinctive features of Euglena acus is its long, whip-like flagellum. This flagellum emerges from a reservoir located at the anterior (front) end of the cell and is used for locomotion, enabling the organism to swim through water.


Chloroplasts: Euglena acus contains numerous chloroplasts, which are small green organelles responsible for photosynthesis. The chloroplasts contain the pigment chlorophyll, which captures light energy and converts it into chemical energy in the form of glucose. This gives Euglena acus its characteristic green colour.


Eyespot: Another unique feature is the eyespot, or stigma, located near the base of the flagellum. The eyespot is a reddish organelle that detects light, helping the organism orient itself towards optimal light conditions for photosynthesis.


Nucleus: Euglena acus has a well-defined nucleus that contains its genetic material (DNA). The nucleus is surrounded by a nuclear membrane and is responsible for regulating cellular activities and reproduction.


Contractile Vacuole: To maintain osmotic balance, Euglena acus possesses a contractile vacuole that expels excess water from the cell. This is particularly important in freshwater environments where this sample was taken, where the organism is constantly taking in water by osmosis.


Paramylon Granules: Euglena acus stores excess energy in the form of paramylon granules, which are composed of a carbohydrate similar to starch. These granules are distributed throughout the cytoplasm and can be used as a reserve energy source when light is insufficient for photosynthesis.


Cytoplasm: The interior of the cell is filled with cytoplasm, a gel-like substance that contains various organelles and supports the cell's metabolic activities.


Ecological Role 

Euglena acus plays several important ecological roles in Northern Ireland's aquatic ecosystems: