Tuesday, June 5, 2007
524

Ecological importance of a freshwater crab (Potomonautes emini) as a macroinvertebrate shredder in an East African stream

Clay Wilton, Department of Biology, Central Michigan University, Brooks Hall, Mt. Pleasant, MI 48859 and Catherine M. O'Reilly, Bard College, 1 Campus Road, Annandale-on-Hudson, NY 12504.

Few macroinvertebrates have been identified in tropical streams, and little is known about their ecology and behavior.  Here, we examined the role of a freshwater crab (Potomonautes emini), as a shredder in streams draining into Lake Tanganyika, Tanzania.  Being the largest invertebrate observed on existing leaf packs, this species was thought to have the potential to contribute significantly to the breakdown of allochthonous organic matter.  In this study, we examined the feeding preference of Potomonautes emini on four common riparian leaf species in the laboratory.  Leaves were collected from four native tree species within the riparian zone of the stream.  All leaves were conditioned in the stream and then cut into 10 cm2 discs.  Leaf discs of each species were placed in laboratory stream chambers with P. emini.  We found that Potomonautes emini strongly and consistently discriminated among leaf species, and that the preferred leaf species was rapidly shredded and consumed.  We suggest that possible differences in nutrient composition, microbial activity, and secondary compounds make the leaves available as a food resource, possibly at distinct times.  Our findings also indicate that P. emini is likely to play a significant role as a shredder in tropical African streams.

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