All type of sexual and a sexual reproduction processes that take place in paramecium is described here.

1. PARAMECIUM
REPRODUCTION
DR. MEENU VARSHNEY
ASSISTANT PROFESSOR ZOOLOGY

2. • Both sexual and asexual reproduction
• Various process of reproduction:
1. Binary fission – Asexual reproduction
2. Conjugation - Sexual reproduction by cross fertilization
3. Autogamy - Sexual reproduction by self fertilization
4. Endomixis – *Nuclear organization and multiplication
* Degeneration of old macronucleus and formation of new by fusion of micronuclei

3. 1. BINARY FISSION (Asexual Reproduction)
• Common method of reproduction
• Occurs transverse at the right angle to the longitudinal axis of the body
• Stops feeding before division and oral groove disappears
• Macronucleus divides by amitosis and micronucleus divides by mitosis then they move
towards the opposite end
• At the same time, the constriction develops at the middle part of the body which divides
cytoplasm into two equal parts
• A fully grown Paramecium is thus divided into two daughter individuals

4. STEPWISE REPRESENTATION OF PROCESS OF BINARY FISSION IN PARAMECIUM

5. • Daughter from anterior end is called protor and from posterior end is called opisthe
• They are of equal size and have a complete set of cell organelles
• Oral groove and cytopharynx are newly formed in both the daughters
• One contractile vacuole goes to protor and another to opisthe.
• Other two contractile vacuoles are newly formed.
• The whole process is completed within 2 hours and may occur one to four times a day.

6. CONJUGATION (A form of sexual reproduction)
• Continuous multiplication by binary fission is interrupted by conjugation as it is necessary
for the survival and rejuvenation of the race.
• Unfavorable conditions like some degree of starvation, shortage of food, a particular
bacterial food, a certain range of light and temperature and certain chemicals induce
conjugation.
• Temporary union of two individuals of same species for mutual exchange of genetic materials

7. • The two Paramecium of opposite mating types come in contact by their ventral surface
during swimming.
• They stick together through their oral groove region
• Cilia,Trichocysts and feeding apparatus degenerate
• Pellicle and ectoplasm degenerate at the point of contact and a cytoplasmic bridge
conjugation bridge is formed
• United paramecia are now conjugants

8. • Changes in macronucleus:
➢The macronucleus breaks up into fragments and these are later absorbed into the cytoplasm
• Changes in micronucleus:
• The micronucleus in each conjugant grows in size and then divides by meiosis to produce four micronuclei
• Out of these four micronuclei, three degenerate and disappear
• The remaining micronucleus divides by mitosis to form two unequal gamete nuclei
• The smaller gamete nuclei is active in migratory in nature and is called migratory gamete nucleus
• The larger gamete is passive and stationary in nature and is called stationary gamete nucleus

9. • The migratory gamete nucleus of one conjugant passes through the protoplasmic bridge into
other conjugant and fuses with its stationary gamete nucleus.
• This fusion results in the formation of a single diploid zygote nucleus (synkaryon) and this
process is called as *amphimixis.
(*The process of complete fusion of two nuclei from two different individuals to form a zygote
nucleus is called as amphimixis.)
• After the formation of zygote nucleus, the attached conjugants separate and now they are
called ex-conjugants.

10. • The zygote nucleus in each exconjugants divides thrice by mitosis forming eight nuclei
• Out of eight nuclei four grow in size to become macronuclei and the rest four small nuclei are called micronuclei
• Then three micronuclei degenerate and disappear.
• The remaining one micronucleus divides mitotically into two
• The exconjugants also divide into two daughter paramecia
• Now each daughter paramecia has 2 macronuclei and 1 micronucleus
• Micronucleus divides mitotically with the division of cytoplasm
• Resulted in four daughter paramecia each with one macronucleus and one micronucleus.
• In this way, 8 paramecia are produced as a result of conjugation four from each conjugant

12. AUTOGAMY (A form of sexual reproduction)
• Autogamy described in Paramecium aurelia by W. F Diller in 1936
• Paramecium aurelia has 1 macronucleus and 2 micronuclei
• Occurs within a single individual
• Macronucleus grows in size then fragmented and absorbed by the endoplasm
• Two diploid micronuclei divide meiotically and produce eight haploid daughter nuclei
• Out of these eight, seven disintegrate
• The remaining one nucleus divides by mitosis and produces two nuclei - gamete nuclei

13. • A temporary protoplasmic cone develops near the mouth.
• Two gamete nuclei enter this cone and fuse together to produce a diploid zygote nucleus
(synkaryon)
• Zygote nucleus divides twice by mitosis to produce four nuclei.
• Two of these nuclei grow to become two macronuclei and remaining two become
micronuclei
• Each micronucleus and the body of paramecium divide to produce two daughter paramecia
• Each paramecia has a macronucleus and two micronuclei

15. ENDOMIXIS (Asexual Reproduction)
• Woodruff Erdmann reported endomixis in Paramecium aurelia. It occurs in single individual
• The macronucleus degenerates and disappears.The two micronuclei divide twice by mitosis
and produce eight nuclei. Six of these eight degenerate
• The Paramecium divides into two. Each daughter Paramecium contains one nucleus.
• The nucleus divides again twice by mitosis to produce four nuclei.Two nuclei enlarge and
become macronuclei and two become micronuclei
• Each micronucleus and the body of Paramecium divide and produce two daughter Paramecia.
Paramecium gets one macronucleus and two micronuclei
• At the end of endomixis four daughter Paramecia are produced from a single individual