Ref ID : 4767
Igor B. Raikov, B.P. Karadzhan, and Raminder Kaur; Fine Structure of Macronuclei and Micronuclei of the Lower Marine Ciliate Trachelocerca obscura (Karyorelictida). Arch.Protistenk 137:25-44, 1989
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Trachelocerca obscura Raikov et Volkonitin (order Karyorelictida) is a large pigmented (dark brown) ciliate from the mesopsammal of the Japan sea. The nuclear apparatus of T. obscura is represented by a single loose group of 7-14 macronuclei (usually including two developing ones) and 2 micronuclei. The micronuclei are filled with condensed chromatin, the lacunae of which enclose curved laminae (chromosomal kinetochores persisting during interphase). These nuclei regularly contain also needle-shaped crystalloids with an oblique periodicity. The micronuclear envelope has practically no pores and is coated externally with a multi-layered capsule of flattened agranular cisternae. The macronuclear envelope, on the contrary, carries numerous pore complexes and lacks multimembranous capsule. Adult macronuclei have large peripheral chromocenters which sometimes fuse into a continuous layer of condensed chromatin. One or two aggregates of nucleoli, micronucleoli, and granular lamellae which are derivatives of the nucleolar cortex, occur nearer to the centre of the nucleus. Many macronuclei contain a microfibrillar sphere which contacts the nucleoli and is often coated with nucleolar granular lamellae. The sphere is resistant to pronase digestion. Some macronuclei also contain bundles of 5-6 nm thick microfilaments which contact the condensed chromatin. Developing macronucler primordia are filled with heterochromatin bodies and lack nucleoli which first appear only in young macronuclei.