Study of Euglena

• Phylum :- Protozoa (Unicellular)
• Subphylum :- Sarcomastigophora (Cilia absent, locomotion by pseudopodia)
• Class :- Phytomastigophora (Chromatophores present in majority)
• Order :- Euglenida (Larger forms with one or more flagella)
• Genus :- Euglena

General Study of Euglena

Euglena is free-living and solitary. It occurs in stagnant water of ponds, pools and ditches with decaying nitrogenous organic matter. During rainy season it is so abundant that it imparts green colour to the water.

Its body is fusiform or spindle-shaped with blunt anterior and pointed posterior end. Its size is microscopic varying from 53- 100u. The blunt anterior end of the body has a funnel shaped depression. Its openings are called cytoplasm or mouth. It leads into a spherical reservoir through a short tube, the cytotpharynx or gullet-The two flagella arise from two tiny granules, the kinetosomes or blepheroplasts lying at the base of the reservoir.

The body is enclosed in a tough but flexible pellicle or periplast that lies inside the plasma membrane and is formed of elastic fibrous protein. Due to toughness pellicle gives a definite form to the body.

Its elasticity permits slight changes in body form. The cytoplasm is distinguished into:an outer thin, clear layer of ectoplasm, an inner granular and more fluid-like central mass of endoplasm.

Its cytoplasmic inclusions are the chromatophores which are oval, disc-like, plate- like or rod[1]like chloroplasts. They possess chlorophyll a and b and help in the synthesis of food. The Paramylon body which is a polysaccharide (B-1, 3 glucon).There is a large contractile vacuole that lies on one side of the reservoir. An orange or red-coloured stigma or eye spot lies in contact with the reservoir that is formed of haematochrome and is sensitive to light.

Euglena progresses in two different ways ie by flagellar movement where the long highly contractile flagellum acts as a locomotory organ and the euglenoid movement, where the pellicle being flexible, permits the organism to perform worm like wriggling movements of the body.

Euglena exhibits mixotrophic type of nutrition i.e as it feeds in more than one way-holophytic or autotrophic nutrition- (Plant-like) in bright sunlight Euglena synthesizes its food from CO2 and water with the aid of chlorophy II (Photosynthesis which is stored in the pyrenoid bodies or is found scattered as paramylum bodies. Saprozoic nutrition or saprophytic nutrition – In the absence of sunlight .Euglena absorbs decaying organic matter by the general body surface .Euglena is sensitive to light as it avoids strong light but moves towards moderate light. It orients itself parallel to a beam of ordinary light and swims towards the source of light. Euglena also reacts to the stimuli of touch, temperature and chemicals.

In Euglena, Respiration is aerobic. It absorbs dissolved oxygen from the surrounding medium by diffusion. In day-time, oxygen is liberated during photosynthesis. During day-time CO₂ produced during respiration is used in photosynthesis Unused CO₂ escapes out by diffusion through body surface. Nitrogenous wastes also escape the same way.In Euglena excess of water is eliminated out by the contractile vacuole. The accessory vacuoles collect excess of water from the endoplasm and release their contents in the main vacuole which gradually increases in size and finally contracts to force the fluid into the reservoir.

Under favourable conditions, Euglena reproduces by longitudinal binary fission, multiple fission and palmella stage- To tide over the unfavourable condition Euglena secretes a gelatinous cyst around its body. Off its flagellum, stops swimming and gets rounded. Euglena divides longitudinally into two but these may divide further forming 4, 16 or 32 daughter individuals. All of them remain entangled in a common cyst forming the so called Palmella stage. On commencement of favourable conditions the cyst and daughter euglenae are set free, which develop flagella and start free existence.

Identifying feature

• Euglena is a unique animal with floral and faunal mode of reproduction having chloroplast occurring in the form of 7-8 thick bodies surrounding a central paramylum granules and scattered pyrenoid bodies.

Special feature

The position of Euglena is still a debatable question as it is considered as an animal by zoologist and plant by botanists. It is included in the kingdom facts.

• The proteinous nature of pellicle and absence of cellulose covering over the body.
• Presence of contractile vacuole.
• Presence of photosensitive stigma or eyespot.
• Saprophytic and even holozoic mode of nutrition among some species of
• Movement from place to place 6. Longitudinal division of the body.