Question

What is the mode of nutrition in Euglena?

Answer 1

Hint: All unicellular eukaryotes, irrespective of their mode of nutrition, are included in the kingdom Protista in Whittaker’s system. Protista includes autotrophic or photosynthetic organisms, consumer-decomposer organisms and protozoans.

Complete answer:

Euglenoids are unicellular, flagellate protists found in water or damp soil. Majority of them are freshwater organisms found in stagnant water. Euglenoid body is spindle-shaped with a blunt anterior end and pointed posterior end. Euglenoids belong to a group of chlorophyllous and non-chlorophyllous flagellate protists, and the largest genera amongst them is the Euglena. Nutrition in Euglena is photoautotrophic. 

However, it is capable of getting nourishment from dead and decaying organic matter in the substrate by secreting digestive enzymes (saprophytic nutrition) in the absence of light. This dual-mode of nutrition is absent in Euglena. Some forms are holozoic (Peranema) or saprobic (Rhabdomonas). So, Euglena is a type of protist (producer-decomposer).

Additional Information: 

Euglena is studied as a plant as well as animal and is called plant-animal.

Plant characteristic present in Euglena:

1. Presence of chloroplast with photosynthetic pigments.

2. Holophytic nutrition.

Animal characteristic present in Euglena:

1. Absence of the cell wall and the presence of the proteinaceous pellicle.

2. Presence of stigma and paraflagellar body.

3. Presence of contractile vacuole.

4. Presence of longitudinal binary fission.

Note: In Euglena the apical end of the cell bears an invagination with three distinct parts, i.e., mouth, canal and reservoir. It helps in the ingestion of solid food particles. 

In Euglena reserve food material is paramylon, stored in the cytoplasm in the form of paramylon granules. They are chemically beta-1, 3-glucan.