Morphology and behavior of crabs and gastropods from Lake Tanganyika, Africa: implications for lacustrine predatory-prey coevolution

The endemic thiarid and viviparid gastropods from Lake Tanganyika have significantly thicker shells and higher frequencies of terminal apertural lip thickening than closely related cosmopolitan taxa from outside the lake. Tanganyikan gastropods also display considerably higher incidence of shell repair, following nonlethal shell damage, than comspolitan taxa of the same families. The endemic Tanganyikan potamonautid crab Platytelphusa armata (a molluscivore) possesses larger, more robust crushing chelae than other African potamonautid or potamonid crabs. Experiments with the endemic gastropods Spekia, Neothauma, Lavigeria spp., Paramelania spp. and the crab Platytelphusa armata showed that increased size, apertural lip thickness or shell sculpture reduced the successful predation rate of P. armata. Crabs with large chelae have a greater ratio of successful:unsuccessful attacks than crabs with small chelae. Among cases of successful predation, crabs with large chelae used predation methods that required less time and energy than the methods used by crabs with small chelae. Data together provide strong support for the idea that the endemic gastropods and crabs of Lake Tanganyika have coevolved over the past 7 M yr. -from Authors