Date of Award


Degree Type


Degree Name

Master of Science




Biology (MS)

First Advisor/Chairperson

Neil Cumberlidge


Lake Malawi is the southernmost lake in the East African Rift Valley and is home to a single species of freshwater crab, the Malawi Blue Crab. Little is known about species diversity and the phylogenetic relationships of the freshwater crabs of Lake Malawi, in contrast to the lake’s highly-diverse cichlid fish species flocks. The Malawi Blue Crab is presently assigned to Potamonautes lirrangensis (Rathbun, 1904) sensu lato, which was originally described from a single female specimen from the D. R. Congo. While the distribution of P. lirrangensis s. l. ranges from the Congo River basin to other Rift Valley lakes, its current taxonomic status remains controversial. Detailed comparative morphological analysis coupled with preliminary DNA sequence data were used to determine the taxonomic status of the Malawi Blue Crab, and to determine the phylogenetic relationships between the Malawi Blue Crab and the freshwater crab fauna of the Lake Malawi basin, particularly the common and widespread species, P. montivagus. The morphological and molecular data presented here indicate that: (1) P. lirrangensis should be restricted to those specimens from the Middle Congo River in the D. R. Congo (referred to here as P. lirrangensis sensu stricto); (2) that the specimens from Lake Kivu formerly assigned to P. lirrangensis s. l. be recognized as a new species (Potamonautes sp. 1); and (3) that the Malawi Blue Crab should be properly referred to as P. orbitospinus (Cunnington, 1907). In addition, it is likely that the specimens from two crater lakes in southwest Tanzania initially identified as P. montivagus belong to a new species (Potamonautes sp. 2).

Access Type

Open Access

Justification for Restricting Access

Temporary restricted access to thesis requested because findings will be published in a scientific journal prior to being made open to the public.