title: The orthonematocyst, a new type of extrusome found in Remanella rugosa and Remanella brunnea (Ciliophora: Karyorelictida).
abstract: A new type of extrusomes has been found in Remanella rugosa Kahl and R. brunnea Kahl (Karyorelictida) at the non-ciliated (left) body side and the non-ciliated rims of the flattened body. The extrusomes are spindle-shaped membrane-bound organelles measuring about 2.5 urn in length and 0.75 μm in diameter. The extrusome consists of a lamellated (myelin-like) outer wall, an apical cone, a thin-walled capsule, and a straight tubular filament inside the intracapsular matrix. Extrusion of the filament has not been observed. The structure of the extrusomes seems to be intermediate between that of the nematocysts of Remanella multinucleata which have coiled filaments [24] and that of toxicysts. They are termed orthonematocysts.
authors.affiliation: Institute of Cytology of the Russian Academy of Sciences, St. Petersburg, Russia.
authors.forename: I B
authors.initials: IB
authors.lastname: Raikov