38.5 Saturday, Jan. 5 The Contributions of Sensory Morphology and Prey Detection Behavior to Trophic Niche Differentiation in Two Sand-Feeding Lake Malawi Cichlids SCHWALBE, M.A.B.*; WEBB, J.F.; University of Rhode Island; University of Rhode Island firstname.lastname@example.org
The adaptive radiations of African cichlids resulted in a diversity of feeding morphologies and strategies, but the role of sensory biology in niche partitioning remains largely unexplored. Fishes in the Lake Malawi genera Aulonocara and Tramitichromis both feed on benthic invertebrates, but differ in sensory morphology and foraging strategies. Aulonocara slowly swims just above the sand and detects flows generated by prey with neuromasts in its widened lateral line canals. In contrast, Tramitichromis fills its mouth with sand and sifts out prey, but the role of the narrow lateral line system (less sensitive than widened canals) in prey detection is unknown. We hypothesized that Aulonocara and Tramitichromis use their visual and mechanosensory capabilities differently while foraging. To test this, we evaluated the ability of Aulonocara stuartgranti and Tramitichromissp. to feed on live and dead adult brine shrimp under light and dark conditions. Prey detection behavior (# prey strikes, detection distance and angle, prey preference [live vs. dead]) was analyzed. Both species ate vigorously in the light, but Tramitichromis detected prey at longer distances and with a narrower range of detection angles than Aulonocara, suggesting a particular dependence on vision. In the dark, Tramitichromis tended not to feed while Aulonocara successfully captured prey and preferred live prey (that produced hydrodynamic stimuli to which the lateral line system responds). Thus, Aulonocara and Tramitichromis, which differ in lateral line morphology, employ distinct foraging and prey detection capabilities, and we hypothesize that these factors are important for trophic niche differentiation in these sand-feeding taxa. Supported by NSF grant IOS-0843307 to JFW, NSF EPSCoR contract EPS-1004057.