EFFECT OF UV-B RADIATION ON CILIATED PROTOZOA - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 229

speed increase. In fact, other motion parameters, such as frequency of directional
changes and frequency distribution of the angles of directional changes, did not show
any dependence on UV-B irradiation 19 .

0,15

Control

0,10

0,05

0,00

0 100 200 300 400 500

Speed [µm/s]

0,15 0,15

O > 370 nm (30 min)

O > 370 nm (60 min)

0,10 0,10

0,05

0,05

0,00

0,00

0 100 200 300 400 500

0 100 200 300 400 500

Speed [µm/s]

Speed [µm/s]

0,15

0,6

0,5

O > 280 nm (60 min)

0,10

O > 280 nm (30 min) 0,4

0,3

0,05

0,2

0,1

0,00

0

0 100 200 300 400 500

0 100 200 300 400 500

Speed [µm/s]

Speed [µm/s]

Figure 3. Histograms of the velocity distribution of samples of red B. japonicum cells under different
irradiation conditions (“visible”= Ot 370 nm, “UV-B”= Ot 280 nm) and times (30 and 60 min)
Redrawn from ref. 18.

The UV-B-induced speed increase was a reversible effect, as shown in Fig. 5,
and the time required for speed recovery depended on irradiation time: for short
irradiation time (3 min 45 s, 7 min 30 s, 15 min) the recovery occurred within about one
hour, for longer irradiation time (30 min, 60 min) it occurred within two hours and for
120 min irradiation speed resumed its initial value after three hours only 19 .