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First published online October 18, 2006
Journal of Experimental Biology 209, 4304-4312 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02521

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Influence of ultraviolet radiation on selected physiological responses of earthworms

Shu-Chun Chuang¹, Wei-Shan Lai¹ and Jiun-Hong Chen^1,2,*

¹ Institute of Zoology, National Taiwan University, No. 1 Roosevelt Road, Section 4, Taipei 106, Taiwan
² Department of Life Science, National Taiwan University, No. 1 Roosevelt Road, Section 4, Taipei 106, Taiwan

^* Author for correspondence (e-mail: chenjh{at}ntu.edu.tw)

Accepted 30 August 2006

The purpose of this study was to investigate the adverse effects of ultraviolet (UV) radiation on earthworms. Earthworms that crawl out of the soil may die within a few hours after sunrise. This study shows that UV exposure can be lethal. In general, UV-B had a stronger damaging effect than UV-A. Different species of earthworms had different tolerances to UV exposure. In this study, Pontoscolex corethrurus showed the highest tolerance of the three tested species to UV radiation, while Amynthas gracilis was the most sensitive. UV radiation induced both acute and chronic responses. The acute response, which occurred immediately on or after UV exposure, was characterized by the appearance of abnormally strong muscle contractions, including S-shaped movements and jumping behavior, possibly caused by bad coordination between the circular and longitudinal muscles. The chronic response included damage to the skin and muscle cells, which resulted in a high mortality rate. Oxygen consumption by A. gracilis was significantly decreased after exposure to UV-A or UV-B. Since the circulation in earthworms is mediated by muscle contraction and the skin is the main organ of respiration, it is reasonable to expect that abnormal muscle contraction and a damaged epithelium could cause suffocation. Because of their sensitive responses, we propose that some earthworms, such as A. gracilis, could serve as a new model for studying UV-induced photodamage.

Key words: invertebrate, ultraviolet, earthworm, crawling behavior, oxygen consumption