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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

View larger version (7K): [in a new window]   Fig. 1. S-shaped movements of Amynthas gracilis exposed to UV-A or UV-B. (A) UV-A exposure. As the dose of UV-A increases, the frequency of the S-shaped movements increases. (B) With UV-B exposure, the same phenomenon is seen.

View larger version (6K): [in a new window]   Fig. 2. Jumping behavior of Amynthas gracilis exposed to UV-A or UV-B expressed as the percentage of individuals showing this behavior. When the earthworms were exposed to less than 1000 J m-2 of either UV-A or UV-B, no individuals jumped. But after exposure to higher doses, abnormal jumping behavior appeared. As the dosages increased, the cumulative percentage of jump individuals was significant increased (2 test, N=30, P<0.001).

View larger version (12K): [in a new window]   Fig. 3. Relative crawling time of earthworms after exposure to either UV-A. The crawling time of P. corethrurus and A. gracilis exposed to 1500 J m-2 of UV-A was significantly increased compared to controls (two-way ANOVA, N=6, *P<0.01), but that of M. posthuma shows no significant difference.

View larger version (14K): [in a new window]   Fig. 4. Relative crawling time of earthworms after exposure to either UV-B. After UV-B exposure, P. corethrurus and M. posthuma show a significantly increased crawling time compared to controls (two-way ANOVA, N=6, *P<0.01), but A. gracilis does not.

View larger version (16K): [in a new window]   Fig. 5. Oxygen consumption of Amynthas gracilis and Metaphire posthuma after UV exposure. (A) After UV-A exposure (1500 J m-2), the oxygen consumption of A. gracilis is lower than that of controls (NEST design, N=6, P<0.01), but that of M. posthuma is not affected. (B) After UV-B exposure (1500 J m-2), the oxygen consumption of A. gracilis is lower than in controls (NEST design, N=6, P<0.01), but that of M. posthuma is not affected.

View larger version (12K): [in a new window]   Fig. 6. Mortality of earthworms after UV-B exposure. (A) M. posthuma shows significant mortality after exposure to UV-B (1000 or 1500 J m-2; two-way ANOVA, N=20, P<0.01), the effect being dose-dependent. (B) A. gracilis only shows significant mortality after exposure to UV-B (1500 J m-2; two-way ANOVA, N=20, P<0.01). In addition, the survival time of A. gracilis was shorter than that of M. posthuma after UV-B exposure (ANOVA, P<0.01).

View larger version (106K): [in a new window]   Fig. 7. Tissue structure of A. gracilis before and after exposure to 1500 J m-2 of UV-B. (A) Cross-section of A. gracilis without UV-B exposure, clearly showing the cuticle (C) and epidermis (E). (B) Section of A. gracilis immediately after exposure to UV-B. The cuticle swelled and the epidermis necrosed. (C) After 2 h exposure, the cuticle shows breakdown, and the epidermis, circular muscle (CM) and longitudinal muscle (L) show necrosis. (D) After 18 h exposure, the epidermis and circular muscle are destroyed and only the longitudinal muscle is present. Scale bar, 50 µm.

View larger version (116K): [in a new window]   Fig. 8. Tissue structure of M. posthuma before and after exposure to 1500 J m-2 of UV-B. (A) Cross-section of M. posthuma without UV-B exposure, showing the cuticle (C) and epidermis (E). (B) Right after UV-B exposure, no obvious damage was seen in the cuticle or epidermis. (C) After 36 h exposure to UV-B, the cuticle and epidermis are pleated, and some epidermal cells show necrosis. (D) After 48 h exposure, the epidermis is destroyed and some circular muscle (CM) is deformed (arrow). L, longitudinal muscle. Scale bar, 50 µm.