| Summary: | Polar Crustacea show high taxonomic and functional diversity and hold crucial roles within regional food webs. Despite the differences in the evolutionary history of the two Polar regions, present data suggest rather similar species richness, with over 2,250 taxa recorded in the Antarctic and over 1,930 noted in the Arctic. A longer duration of isolated evolution resulted in a high percentage of endemic species in the Antarctic, while the relatively young Arctic ecosystem, subjected to advection from adjacent seas, shows a very low level of endemism. Low temperatures and seasonal changes of food availability have a strong impact on polar crustacean life histories, resulting in their slow growth and development, extended life cycles, and reproduction well synchronized with annual peaks of primary production. Many species, Antarctic amphipods in particular, exhibit a clear tendency to attain large size. In both regions, abundant populations of pelagic grazers play a pivotal role in the transport of energy and nutrients to higher trophic levels. The sea-ice habitat unique to polar seas supports a wide range of species, with euphausiids and amphipods being the most important in terms of biomass in the Antarctic and Arctic, respectively. Deep sea fauna remains poorly studied, with new species being collected on a regular basis. Ongoing processes, namely a decline of sea-ice cover, increasing levels of ultraviolet radiation, and invasions of sub-polar species, are likely to reshape crustacean communities in both Polar regions.
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