Nuclear functions in postconjugational development ofParamecium caudatum: Ability to form food vacuoles analyzed by nuclear elimination and implantation

✍ Scribed by Mikami, Kazuyuki

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 680 KB
• Volume: 13
• Category: Article
• ISSN: 0192-253X
• DOI: 10.1002/dvg.1020130308

✦ Synopsis

Paramecium caudatum loses the ability to form food vacuoles at the crescent stage of the micronucleus from 5 to 6 hr after the initiation of conjugation and regains it immediately after the third division of the zygotic nucleus. To assess the micronucleor function in the development of the oral apparatus after conjugation, prezygotic micronuclei was removed from cells at various stages of conjugation, and their ability to form food vacuoles were examined. 1 ) When all of the prezygotic micronuclear derivatives were eliminated before the stage ot tormation ot the zygotic nucleus, the exconjugant did not regain its ability.

2. When a zygotic nucleus or postzygotic nuclei were removed, in some cases the cell formed as many food vacuoles as did nonoperated cells after conjugation, while in other operated cells the number of food vacuoles was subnormal. 3) When a micronucleus from a cell at vegetative phase ( G l ) was transplanted into a cell of an amicronucleate mating pair at the stage between 8 and 9 hr after the initiation of conjugation, the implanted cell regained the ability to form food vacuoles. However, no cell regained the ability when the implantation was carried out within 1 hr after the separation of the mates. The results show that the micronucleus plays an indispensable role in the development of the oral apparatus at the stages of exchange of gametic nuclei and fertilization and that the micronucleus transplanted from asexual cells con fulfill this function. O n the other hand, removal of the macronucleus from exconjugants showed that the maternal macronucleus also has an indispensable function in regaining the ability to form food vacuoles. 0