Gammarus: important taxon in freshwater and marine changing environments
Gammarus spp. consist of more than 100 freshwater, brackish, and marine species in the Northern hemisphere. They represent important keystone species in aquatic ecosystems and are often present in high abundance. As shredders and detritus feeders, they contribute to the detritus cycle and the microbial loop. Gammarids are also carnivorous, feeding on small invertebrates and carrion. Due to their widespread distribution, significance in the food web, and sensitivity to a wide range of pollutants, they are important bioindicators for water quality assessment. Gammarus spp. are ecologically highly successful due to the following characteristics wide trophic repertoire and foraging plasticity, migration ability and tendency to drift, which allows them to easily invade and colonize ecosystems, high reproductive capacity with several broods per female per year, and a high number of offspring and relatively longevity (1-2 yrs).
Gammarus spp. and their American relative Hyalella azteca are standard test species in ecotoxicity testing in the USA and UK. A new OECD test guideline is currently being prepared for gammarids, which will consist of a variety of in situ and ex situ ecotoxicological studies based on different measurement parameters.
The evolution of gammarids is particularly interesting gammarids contain several Ponto-Caspian and Atlantic invasive species, which have spread throughout Europe. Some species are currently being divided into several geographical forms. Although the genome of Gammarus pulex has yet to be sequenced, 12345 expressed sequence tags are known, which might be the basis for future innovative knowledge in taxonomy and toxicogenomics.
Despite the taxon's importance in different fields of biology (e.g., ecology, evolution, ecotoxicology, taxonomy,...