cells possibly are instead produced less during the breeding season because increased testosterone levels may decrease immune responses. Additionally, this finding indicates males are at a greater risk from UVB radiation, as well as parasite and pathogen infection, during the breeding season. The role of schreckstoff as an immune response has additional implications in this age of increasing environmental change. Environmental stressors, including UVB radiation, pollution, and parasites, are increasing in the environment, and are likely to continue increasing over time. UVB radiation exposure is increasing due to decreases in stratospheric ozone, diseases are becoming increasingly important at both local and global scales, and pollutants, including heavy metals, are being introduced into ecosystems. If cadmium, the heavy metal affecting the fish's ability to produce schreckstoff in response to environmental stressors, increased in concentration in the environment, the immune response of many ostariophysan fishes would be compromised. References Sources Argentini, M. 1976. Isolierung des Schreckstoffes aus der Haut der Elritze Phoxinus phoxinus (L). University of Zurich. Atema, J., and D. Stenzler. 1977. Alarm substance of the marine mud snail, Nassarius obsoletus: Biological characterization and possible evolution. Journal of Chemical Ecology 3:173-187. Blaustein, A. R., J. M. Kiesecker, D. P. Chivers, and R. G. Anthony. 1997. Ambient UV-B radiation causes deformities in amphibian embryos. Proceedings of the National Academy of Sciences in the USA 94:13735-13737. Brown, G. E., J. C. J. Adrian, E. Smyth, H. Leet, and S. Brennan. 2000. Ostariophysan alarm pheromones: laboratory and field tests of the functional significance of nitrogen oxides. Journal of Chemical Ecology 26:139-154. Chivers, D. P., G. E. Brown, and R. J. F. Smith. 1996. The evolution of chemical alarm signals: Attracting predators benefits alarm signal senders. The American Naturalist 148:649-659. Chivers, D. P., and R. J. F. Smith. 1994. Intra- and interspecific avoidance of areas marked with skin extract from brook sticklebacks (Culea inconstans) in a natural habitat. Journal of Chemical Ecology 20:1517-1523. Chivers, D. P., B. D. Wisenden, C. J. Hindman, T. A. Michalak, R. C. Kusch, S. G. W. Kaminskyj, K. L. Lack, M. C. O. Ferrari, *R. J. Pollock, C. F. Halbgewachs, M. S. Pollock, S. Alemadi, C. T. James, R. K. Savaloja, C. P. Goater, A. Corwin, R. S. Mirza, J. M. Kiesecker, G. E. Brown, J. C. J. Adrian, P. H. Krone, A. R. Blaustein, and A. Mathis. 2007. Epidermal 'alarm substance' cells of fishes maintained by non-alarm functions: possible