Organisms such as Strombidium sulcatum are classified as ciliates because the cell membrane has many hairlike projections, called cilia, that are used in locomotion.
In Strombidium sulcatum, the cilia are restricted to a collar at one end of its spherical body. There is no test. Among protists, ciliates have the most complex cells, with two nuclei. The macronucleus is needed for growth and reproduction, and the micronucleus is essential for sexual reproduction. Strombidium sulcatum reproduces asexually by splitting in two, but during sexual reproduction, two cells join together for a considerable period and swap parts of their micronuclei. When the genetic composition of the joined micronuclei has become identical, the cells separate again. Further changes occur and both cells then split into two. This form of sexual reproduction is called conjugation.
- Kingdom Ciliata
- Diameter 0.045 mm
- Habitat Surface waters
- Distribution Atlantic, Pacific, and Indian oceans