Ciliary Organelles and Associated Fibre Systems in Euplotes Eurystomus (Ciliata, Hypotrichida)

Abstract

Euplotes eurystomus bears 8 rows of single, non-motile simple cilia, 18 ventral cirri, and a row of adoral membranelles. Each cirrus contains 40-120 cilia in tight hexagonal packing, and each membranelle consists of 3 rows of 10-40 cilia; the component cilia adhere together in life, but no means of adhesion, other than small protuberances of the ciliary membrane, has been seen. The kinetosomes of compound organelles, but not of the simple cilia, are associated with rootlet fibres. The kinetosomes of the component cilia of compound organelles are linked together at two levels by characteristic arrays of fibres. Single rootlet microtubules (about 20 mµ in diameter) interconnect individual kinetosomes of adjacent membranelles, but the rootlet microtubules arising from cirri are found as bundles, each of which corresponds to one of the fibres seen in the light microscope. The bundles of microtubules of most cirri arise at dense bars near the edge of the cirrus base, and terminate at or near the pellicle, without interconnecting cirri directly or indirectly. The rootlet microtubules of the anal cirri run the length of the base of the cirrus near the inner end of the kinetosomes and join into large bundles; these run anteriorly to join with each other and attach to the distal end of the membranelle row. The anal cirri and the adoral zone of membranelles form one structurally united part of the locomotor apparatus.