Global panorama of studies about freshwater oligochaetes: main trends and gaps

Freshwater oligochaetes have been studied over the years in a wide range of habitats around the world. To analyse the data published about freshwater oligochaetes in the 31 year period between 1985 and 2015, we searched for documents in the ISI Web of Science, Scopus and SciELO databases. A total of 979 works were evaluated from 184 periodicals. The United States is the country with the most publications about aquatic oligochaetes, followed by France, Germany and Italy. Works related to the ecology and ecotoxicology of these organisms are most abundant. Studies carried out in the laboratory are most frequent, consisting of investigations involving bioassays, morphology, genetics and molecular biology. The results also show that spring, cave water bodies and swamps have been studied less than any other aquatic habitat and that countries of the Southern Hemisphere are under-represented in the studies of aquatic oligochaetes. Hence, there is a need for increased efforts to fill in gaps in the knowledge about these oligochaetes