Question

Which one of these species has one mega nucleus and two micronuclei?
A. Paramecium Aurelia.
B. Paramecium bursaria.
C. Paramecium caudatum.
D. Paramecium multimicronucleatum.

Answer 1

Paramecium has two kinds of nuclei, one is a large ellipsoidal nucleus called a macronucleus and other is (at least) one small nucleus called a micronucleus. Paramecium cannot survive without the macronucleus whereas it cannot reproduce without the micronucleus.

Complete answer:
-Paramecium aurelia comes under phylum ciliophora and are unicellular organisms. All the components of the cells are dispersed in cytoplasm. As it is a complex organism, it has two types of nuclei i) one mega nucleus and ii) two micronuclei. The metabolism such as feeding and maintenance is controlled by the mega nucleus and it is polyploidy. Whereas in reproduction the micronucleus plays an important role, and is diploid.
-Paramecium bursaria is about 80-150micrometers in length, with one wide oral groove, two contractile vacuoles, and a single macronucleus as well as a single micronucleus. P. bursaria is the only species of Paramecium that forms symbiotic relationships with algae.
-Paramecium caudatum is 170–330 micrometres long (usually 200–300 micrometres). This species of paramecium has two nuclei i) a large macronucleus and ii) a single compact micronucleus. It cannot survive without the macronucleus and without micronucleus it cannot reproduce.
-Paramecium multimicronucleatum is about 200-350 micrometers in length and is the largest of the commonly studied paramecia. It contains one macronucleus and three to four micronuclei. It is a unicellular organism and exhibits the property of movement by using cilia or ciliary-derived structures.
Hence, the correct option is (A) Paramecium Aurelia.

Note:
-In paramecium, the macronucleus is the centre of all metabolic activities. The micronucleus acts as a storage site for the genetic material and contains copies of chromosomes. It gives rise to the macronucleus and which is responsible for the genetic reorganization that occurs during conjugation.
-Paramecium species have two types of nuclei, each differ in their shape, number, content and function.