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2M - Monitoring of function and structure (WEP/139) Intersexuality in Gammarus fossarum − occurrence and causes. Jungmann, Dirk1, Petzsch, Patrick1, Ladewig, Vanessa1, Nagel, Roland1, 1 Dresden University of Technology, Dresden, Saxony, Germany ABSTRACT- Intersexuality in the amphipod Gammarus fossarum was discovered first in the stream Lockwitzbach (Germany). The phenomenon is described for other gammarids too, however, the real cause of intersexuality is still unknown. Sex differentiation in gammarids is controlled by hormones. Hence, the cause of intersexuality seems to be an effect of endocrine disruption by chemicals, however, the occurrence of intersexuality might also be normal in the aquatic environment. We examined the occurrence of intersexuality in different populations of G. fossarum followed by an active effect monitoring in the field and laboratory. In 5 German streams a total of 8 sampling sites were investigated and the proportion of intersex varied greatly between the streams (0.2% to 24% of adults), however, were relatively constant at the sampling sites. In the population of the Lockwitzbach intersexuality occurs over an investigated period of 2 years. At 3 sampling sites the pooled data showed an abundance of intersexuality of 13%, 7.1% and 12%, respectively. In contrast intersexuality occurs seldom in the streams Koersch and Zschonerbach with an abundance below 1%. Intersex animals of G. fossarum are functional females and exhibited female behaviour. The median size of females in natural populations is smaller compared to males. The size of intersexes in the Lockwitzbach was significantly larger compared to females but was not different to males. Animals from Zschonerbach (lowest occurrence of intersexuality) were exposed in the Lockwitzbach and in the laboratory to Lockwitzbach water. The proportion of intersexuality increased significantly in these exposed animals to 4.2 and 4.6%, respectively, compared to the population from the Zschonerbach. Hence, a factor in the water significantly influences the abundance of intersexuality. This is an indication, however, no proof that xenobiotics are responsible for intersex induction in G. fossarum. Key words: Intersexuality, Gammarus fossarum, active effect monitoring, fieled and laboratory experiments |
