Reproduction
Pseudomicrothorax dubius, silverstained cell showing the three adoral membranelles, the rows of somatic cilia, the sausage-shaped macronucleus and the spherical micronucleus. © William Bourland
Reproduction in ciliates is most commonly asexual, ocurring by binary fission. Sexual reproduction, which in ciliates is by a process of conjugation, is less common and has yet to be described for Pseudomicrothorax dubius.
Binary fission involves the replication of all ciliary and other structures prior to cell division. The process by which this occurs provides clues to a ciliate's evolutionary relationships. Of particular importance is the development of the oral ciliature (Foissner, 1996).
In P.dubius:
- the paroral membrane is derived from the parental structure
- the adoral membranelles originate from the leftmost rows of body cilia
- the parental oral ciliature is almost entirely reorganised
This indicates that P. dubius may be related to the hymenostome ciliates. It has even been suggested that P. dubius is a missing link between the hymenostome and gymnostome ciliates (Shi, 1980a)
The process of binary fission in P. dubius is described in detail by Thompson and Corliss (1958), Peck (1974) and Shi (1980).