Non-indigenous invasive freshwater crustaceans (Crustacea: Malacostraca) in Slovakia - page 6

Isopoda

Jaera sarsi Valkanov, 1936 is the only species of the genus Jaera that occur in the main course of the Slovak section of the Danube River (Figure 11). Brtek (2003) described a new species to science found in the Danube River in Slovakia, the Jaera danubica Brtek, 2003. The recent study by Borza (2012) revealed that J. danubica is merely a product of the time lag between the molting of the different body regions. The change in shape of the J. danubica was affected by the lateral (and the concurrent longitudinal) growth of the anterior half of the body (Borza, 2012). Jaera istri Veuille, 1979 was described based on J. sarsi (Nesemann et al., 1995; Brtek, 2003) however, the concept received criticism, implying that the characteristics distinguishing J. istri from J. sarsi fall within the confines of intraspecific variability (Borza, 2012). Occurrence of the species in Slovakia can be dated back to the 1930s (Strouhal, 1939; Brtek, 1953). J. sarsi is a species that extended its range of occurrence in the Southern corridor reaching the Main-Danube canal, from where it spread further to Western Europe through the Rhine River (Tittizer and Banning, 2000; Bij de Vaate et al., 2002).

Mysida

Limnomysis benedeni Czerniavsky, 1882 was the first species from the order Mysida known in the Slovak part of the Danube River (Figure 12) (Brtek and Rothschein, 1964). The species extension route is the Southern corridor and its extension is well documented (Bij de Vaate et al., 2002). The species successfully invaded the whole Southern corridor and is to be found in the Dutch Rhine River section as well (Kelleher et al., 1999).

Hemimysis anomala (Sars, 1907) is one of the most successful invaders of European inland and coastal waters and continues to colonize new areas (Borza, 2008). The species is photophobic and is active at night forming pelagic swarms. H. anomala avoids strong current and during the day hides in the deeper waters (Borza, 2007; Borza, 2008). The species was first recorded in the Slovak stretch of the Danube in 2005 by Wittmann (2007) (Figure 12).

 

Fig11
Figure 11: Distribution of J. sarsi according to Elexová et al. (2010) (circles) and the research in 2011 (triangles).

 

Fig12
Figure 12: Distribution of H. anomala (squares), K. warpachowskyi (circles) and L. benedeni (diamonds) according to research of Wittmann (2007) and Elexová et al. (2010).

 

Katamysis warpachowskyi Sars, 1877 is a Ponto-Caspian species that extended its range in the upper and middle Danube River. It was found for the first time in 2001 at several sites of the Austrian, Slovakian and the Slovakian-Hungarian reach of the Danube (Figure 12) (Wittmann, 2007; Borza, 2007). The species prefers deeper waters and tolerates strong current (Borza, 2007).

 

Conclusions

There are 17 non-indigenous invasive higher freshwater crustacean species (class Malacostraca) known to occur in Slovak waters and some of them have become a permanent part of the zoocenosis in the country (Figures 1-12). Our data shows a lack of native crustaceans from each locality inhabited by the alien ones. Invasive species occur only in the main course of the river. Non-indigenous amphipod species showed that they are more tolerant to the conditions of the Danube River and are more fecund compared with the native ones. Alien freshwater crayfish species are more tolerant to the environmental and biological conditions as well, thus the expansive character of the species is to be expected. Monitoring of the development of the aquatic ecosystems invaded by the non-indigenous species and identification of its development is of vital importance for conservation management implementation strategies. In the future new invasive species are expected in Europe, representing one of the major problems facing scientists in the 21st century.

 

Acknowledgements

The author would like to thank Katarína Necpálová for her help with identification of amphipods and, Barbora Vitázková and Vladimír Janský for their support and provided data.