Growth, breakdown, repair, and rapid contraction of microtubular axopodia in the heliozoan Actinophrys sol

Morulate bodies in Actinophryid heliozoa: A fixation artefact derived from microtubules?

“…This co-existence could only be harmonized with the concept that morulate bodies are derived from axonemes if we assume that different axonemes within one cell have different degrees of stability. This suggestion is not implausible as we know that selective breakdown and reassembly of axonemes is employed during heliozoon feeding, movement and cell division (9)(10)(11)(12)28 …”

Axopodial Contraction in the Heliozoon Raphidiophrys contractilis Requires Extracellular Ca2+

“…In actinophryid heliozoons such as Actinophrys sol and Echinosphaerium akamae , axopodial contraction can be induced only when a prey cell attaches to the axopodial surface, and mechanical stimulation is not effective in inducing contraction (Kitching, 1960;Ockleford and Tucker, 1973;Suzaki et al ., 1980). In centrohelid heliozoons such as Ciliophrys and Heterophrys , on the contrary, axopodial contraction has also been reported to be induced by mechanical stimulation (Davidson, 1969(Davidson, , 1973.…”

“…Rapid axopodial contraction in actinophryid heliozoons also belongs to this class of motility . In actinophryid heliozoons such as Actinophrys and Echinosphaerium , rapid axopodial contraction occurs when a prey protozoan attaches to the tip of an axopodium, and the food organism is conveyed by the contraction toward the cell surface (Ockleford and Tucker, 1973;Suzaki et al ., 1980, Kinoshita et al ., 2001. Recently, we have shown that Ca 2+ -dependent contraction of the "contractile tubules structure (CTS)" is responsible for the axopodial contraction in Actinophrys sol and Echinosphaerium akamae .…”

Microtubules in Protozoan Cells. IV. Effects of Sulfhydryl-Blocking Reagents on Axopodial Degradation and Reformation in Heliozoa

“…Several studies have revealed that heliozoan microtubules, as well as those in the mitotic apparatus, are conspicuously labile to various physical and chemical stimuli such as hydrostatic pressure (2,5,23), low temperature (10,22,24), colchicine (4,10,21,24), light metal ions (18,19), heavy metal ions (14,16), dilute urea (17), and concanavalin A (25). Roth,Vollet and Davidson (15) also have demonstrated that the cell surface itself may be involved in regulating various conditions of the axonemal microtubules and that some of these actions can be experimentally and reversibly controlled.…”