MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(ARI-1117-790219) Effects of nonylphenol on the molting cycles of estuarine mysid shrimp Americamysis bahia.

Hirano, M¹, Ishibashi, H², Watanabe, N¹, Iwasaki, Y¹, Miyazaki, H¹, Arizono, K¹, ¹ Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto² Center for Marine Environmental Studies, Ehime University

ABSTRACT- The present study aimed to examine the effects of exposure to a xenoestrogen, nonylphenol (NP) on a marine crustacean, the mysid shrimp Americamysis bahia. Seven-days-old mysids were exposed to the nominal NP concentrations of 0.3, 1, 3, 10 and 30 microg/L for 14 days. The body length of the A. bahia was significantly decreased relative to the controls when exposed to 1, 3, 10 or 30 microg/L NP for 14 days. Moreover, the carapace length was significantly decreased in the 10 or 30 microg/L NP treatment groups, and the body weight exposed to NP of 30 microg/L for 14 days was also significantly decreased relative to the controls. Although the induction of immature gonad found in the 30 microg/L NP treatment group, no significant differences were observed in sex ratio with the appearance of secondary sex characteristics. The total number of molting exposed to NP for 14 days was significantly decreased in the treatment groups at 10 or 30 microg/L relative to the controls. However, no significant differences were observed in the 20-hydroxyecdysone levels in A. bahia at the end of NP exposure for 14 days in the control, solvent control and all NP treatment groups. Moreover, no abnormal sexual differentiation in gonads of mysid was observed in any of groups treated with NP. These results suggest that exposure to environmentally relevant concentrations of NP affected the development of A. bahia that were linked to delays in molting cycles.

Key words: Americamysis bahia, nonylphenol, molting cycle, 20-hydroxyecdysone