Cation regulation and alteration of water permeability in the amphipod Dikerogammarus villosus: an indicator of invasion potential
Brooks, Steven J.; Platvoet, Dirk; Mills, Chris Lloyd
published: Sep 5, 2008
ArtNo. ESP141017203002, Price: 29.00 €
The freshwater amphipod Dikerogammarus villosus (Sowinsky) can devastate gammarid communities that it invades. We investigated aspects of osmoregulation in D. villosus to determine whether it could adjust to altered salinity. D. villosus maintained relatively constant haemolymph Na+ concentration up to an acclimation salinity of 10 ‰, and haemolymph K+, Ca2+ and Mg2+ concentration up to a salinity of 16 ‰. Increasing acclimation salinity above 16 ‰ induced sharp increases in haemolymph cation concentrations, suggesting osmoregulatory dysfunction. Both sodium influx and the half time of exchange of water (t1/2) fell with increasing acclimation salinity. In addition, sudden transfer of freshwater acclimated D. villosus to 20 ‰ produced a rapid reduction in sodium influx to the rate found in amphipods acclimated to 20 ‰. This indicates that D. villosus can regulate water permeability and sodium influx, both of which are important osmoregulatory mechanisms in euryhaline gammarids. In conclusion D. villosus poses a serious invasion risk to areas accessible via transit through brackish water of salinity 20 ‰ or less. It is therefore recommended that complete mid ocean ballast water exchange is practiced, to reduce the risk of introduction of D. villosus to areas currently free of this amphipod, e.g. North America and the Great Lakes.