Is there an orientation-dependent excursion of the Müller body in the ”statocystoid" of Loxodes ?

Abstract

The ciliate Loxodes possesses a number of vesicles at its anterior dorsal margin. These so-called Muller vesicles contain a spherical inclusion (Muller body) in which lie crystals of barium salts. The Muller body is connected via a stalk to the wall of its vesicle. It is presumed to function as a stato-organelle and to respond by visible motions to changes of the direction of gravity. We have attempted to document the motion of the Muller body with respect to the direction of the gravity vector. Living cells moving in a horizontal or a vertical plane have been viewed under the light microscope with differential interference contrast, documented on video film, and sequences of single frames have been evaluated. Apparent excursions of the Muller body by about 1.5 μm, corresponding to a deviation of 10° at the base of the stalk, are observed in cells moving in a horizontal plane. No larger excursions have been seen in the vertical plane. Implications of this result for a model of the stato-organelle are discussed.

Biomineralization in Ciliates

“…The fresh-water ciliate Loxodes forms crystals of barium sulfate (BaSO 4 , barite) as gravity sensors (Fig. 1) [12,13]. This so-called Müller bodies are spherical crystalline structures, with a diameter of 3-3.5 µm.…”

“…Located within the Müller vesicles they are fixed to a modified ciliary stalk. Therefore, they are also described as mechanosensors or statocysts [12,14,15]. Within the Müller's bodies of Loxodes nothing but Ba was detected, thus it was assumed that they are able to selectively enrich Ba and that they play an important role for lacustrine barium chemistry [13,16].…”

Gravitational Zoology: How Animals Use and Cope with Gravity

“…In contrast to Paramecium, another ciliate -Loxodesseems to perceive gravity via particular intracellular organelles, called "MUller-bodies", which consist of a membraneous pouch, containing a "heavy body" or "statolith" of BaS04 (Fig. 20.4) [15] (see also Chap…”

Graviresponses of certain ciliates and flagellates

“…These organelles are specialized vacuoles (7-10 m in diameter) containing a heavy body of BaSO 4 (3-3.5 m in diameter, density 4.5 g/cm 3 ), the Mü ller body, fixed to a modified ciliary stalk (50,51). Concerning the mechanism, it is proposed, in analogy to the graviperception of metazoa, that gravity is perceived by bending of a ciliary complex, which changes the membrane potential, which in turn determines the activity of the cilia and thus the swimming activity of the cell (51,52). Cultivation for up to 12 days in space did not affect the general morphology of the Mü ller vesicles, although there were first indications for less mineralization in Loxodes cells under microgravity without impact on the graviresponse, which was tested after the mission on the ground (44).…”