Pattern Variability in Microtubular Arrays Associated with the Tentacles of Actinobolina (ciliatea: Gymnostomatida)

Structural-functional roles of microtubules in cells and cell appendages are becoming well established . A "static" supportive function could be assigned to the microtubular arrays in the axonemes of Heliozoa (Actinophrys, 7 ; Echinosphaerium, 18) and Radiolaria (Nassellaria, 5), in the tentacles of Suctoria (Acineta, 3 ; Tokophrya, 12), and in the endosprits of the ciliate Cyathodinium (9) . Models for "dynamic" functions of microtubular arrays have been proposed for the ciliary axoneme (4, 13, 15), the coccid sperm flagellum (11), the extension of heliozoan axonemes (16), and the transport of cellular substances (2, 19) . A new pattern of microtubular arrays is revealed within the retractable tentacles of the curious gymnostome ciliate Actinobolina. This note briefly describes the array, reports on its variation, and suggests a functional model for tentacle extension and retraction .