**Bräucker R, Machemer-Röhnisch
S, Machemer H, Murakami A (1992) Gravity-controlled gliding velocity
in***Loxodes***. **
**Summary **
The locomotion of *Loxodes *as controlled by
the natural gravity vector was investigated employing a mass-cell
approach. Samples of cells were incubated for 4 hours in a 1.6 mm
deep well (41 x 85 mm) filled with defined experimental solution.
Their gliding locomotion on surfaces inclined between 0° and
90° was recorded by videocamera. Steady gliding rates (median
of total: 206 µm/s; n = 12711) were evaluated by calculating
the vertical component from observed tracks. At a given inclination
the rates of downward and upward gliding were similar. The sedimentation
rate of freely suspended nickel-immobilized specimens (S = 49 µm/s),
and vertical rates of displacement at 6 differently inclined planes,
and with cells in "sitting" posture as well as "hanging"
(upside down), were used to determine the gravity-dependent component
(delta = -49 µm/s) during gliding motion. Numerical equality
of the gravity force to produce S and of the counterforce to produce
delta follows from the observed constancy of gliding rates and identical
medians of vertical locomotion up and down (169 µm/s). It
is concluded that neutralization of sedimentation is a precondition
for Loxodes to migrate along a vertical O_{2} gradient in its freshwater habitat. |