Question

Identify the correct sequence of events with reference to conjugation of vorticella.
(A) Amphimixis (B) Disappearance of macronucleus
(C) Attachment of the conjugants (D) Post conjugation fissions
(E) Prezygotic nuclear divisions (F) Post zygotic nuclear divisions

• A. C$\to$B$\to$E$\to$A$\to$F$\to$D
• B. F$\to$A$\to$D$\to$B$\to$C$\to$E
• C. F$\to$D$\to$A$\to$E$\to$B$\to$C
• D. C$\to$B$\to$A$\to$E$\to$D$\to$F

Answer 1

The correct option is A C$\to$B$\to$E$\to$A$\to$F$\to$D

Vorticella monilata is a protozoan of sub-phylum Ciliophora. Class ciliata of subphylum Ciliphora is further divided into 4 subclass. Holotrichia, Suctoria, Spirotrichia and Peritricha. The latter Peritricha consists of order -Peritrichida to which Vorticella belongs. Adult Vorticella is characterized without body cilia, while apical ends with buccal cilia. It common name is bell animal-cule. Conjugation is anisogametogony type. Gametes are formed by longitudinal and unequal binary fission. Macroconjugant is sedentary and stalked, while microconjugate (male) attach to the female conjugate (macroconjugate) within 24 hours. After attachment with macronuclei, in both conjugants disintegrate and disappear. (Seven and three number of daughter nuclei disintegrate and disappear in male and female conjugants respectively)In prezygotic divisions micronucleus of male and female conjugants undergoes meiosis I and II and produces 9 daughter nuclei and 4 daughter nuclei respectively. Now male pronucleus and female pronucleus are formed in conjugants only and the merger of two nuclei and the cytoplasm of two conjugants is termed as amphimixis. It does not take place in microconjugant and resultant nucleus of amphimixis is known as synkaryon. Such conjugant, located in female conjugant is called zygote; microconjugant persists after conjugation. Division after formation of zygote are called postzygotic nuclear divisions and three such divisions take place in Vorticella - the resultant nuclei in post zygotic divisions are eight. Among eight nuclei, 7 nuclei are changed to macronuclei and 1 is changed to micronucleus during postzygotic divisions. Zygote having 7 macro and 1 micronucleus undergoes fission thrice and are called post conjugate fission.

Thus, the correct answer is option A.