Lethal effects of UV-radiation on lumbricid earthworms (Eisenia fetida andLumbricus terrestris)

The detrimental effects of solar radiation, in particular its UV-B componen t, on lumbricid worms on the surface of the ground have been analyzed. Eise nia fetida and Lumbricus terrestris were irradiated with a quasi-solar ligh t-spectrum including visible (VIS) and UV wavelengths. With a special filte ring technique the spectral composition in the UV range was varied without changing the total quantum yield: VIS + UV-A or VIS + UV-A + UV-B. As a con trol, the animals were also exposed to visible radiation alone. Even radiat ion limited to the visible range had lethal effects on the animals. Under n atural VIS intensities worms died within a day. The lethal duration was fur ther shortened by adding UV-A to the spectrum and shortest when quasisolar UV-B was also present. The lethal radiation time (LT 100) decreases exponen tially with increasing radiation intensities regardless of spectral composi tion in the UV-range, approaching a limit of ca. 7 h under UV-B for both lu mbricid species. At low intensities, however, L. terrestris lives considera bly longer than E. fetida. The LT 100 cannot be decreased unlimited by rais ing intensity, within the range of natural solar radiation, because the ani mals have protective mechanisms (pigmentation, mucus) that enable them to s urvive for some time under UV.