portrait

Descrição:

Portrait of Metacystis recurva (Penard,1922), a loricate prostomatid ciliate. The body is elongate but quite contractile. The anterior is bluntly truncate and the posterior broader and rounded. There is usually a distinctive large clear protuberant posterior vacuole but this may be lacking (as in this case) leading to confusion with the similar genus, Vasicola. The oral aperture is apical, surrounded by four rows of peribuccal cilia. The kinetids of the longitudinal kineties line up with one another to form horizontal rows called paratenes. The cell surface may be transversely furrowed along these paratenes. There is often a long laterally located posterior cilium (not seen here). The central macronucleus and posterior contractile vacuole are not well seen here. The highly refractile material in the neck of the cell is an aggregate of cytoplasmic crystals. The lorica is a narrow curved truncate cone shape open at the anterior end with 12-15 transverse corrugations (thanks to Martin Kreutz for his translation of Kahl’s species description). The lorica is nearly colorless in young individuals and becomes sepia color with age, presumably due to deposition of minerals. The overlying cladocercan shell distorts the color in this image. Loricae are often found inside the vacant shells of cladocercans. Metacystis is said to feed on sulfur bacteria. From sapropelic freshwater aquaculture tank near Boise, Idaho. DIC optics.