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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Food webs 2
Freshwater crabs may be Africa's missing shredders.
M.K. Dobson. Department of Environmental and Geographical Sciences, Manchester Metropolitan University, Chester Street, Manchester, M1 5GD, UK
Invertebrate shredders are apparently rare in the tropics, despite the often high biomass of potential food resources. Africa, for example, is devoid of most of the 'classic' shredder groups, such as Limnephilidae, Gammaridae and Nemouridae. What Africa does possess, however, is freshwater crabs (Decapoda), with over 100 species so far identified. I collated published information about African freshwater crabs, complemented by field and laboratory studies in Kenya. Freshwater crabs are often extremely abundant, particularly in streams with undisturbed riparian vegetation, and commonly account for over 70% of total macroinvertebrate biomass. Although freshwater crabs are opportunistic feeders, the predominant food for most species is detritus, particularly among adults. In turn, they are a major food resource for a variety of vertebrate predators, including humans in some localities. The evidence currently available suggests that crabs are significant shredders in African streams. It also highlights the terrestrial foraging activity of many species, suggesting that they may be important in the transfer of energy between land and water.
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