Water flows shape lateral line morphology in an arid zone freshwater fish

Question: Trait plasticity can act to buffer populations from human impacts, but can sensory traits be plastic? Hypothesis: Early exposure to water flows affects the development of the lateral line sensory system in fishes. Organism: Western rainbowfish (Melanotaenia australis). Methods: Juveniles of wild-caught fish were allocated to replicate fast- or slow-flow channels and the morphology of the lateral line system was evaluated using fluorescence imaging. Results: Exposure to water flows influenced the development of the lateral line sensory system depending on the body region of the fish sampled. Fish reared in fast water flows had more sensory cells on the tail fin and fewer in the nasal region than those raised in slow flows. Sensory plasticity can potentially allow populations to persist in modified flow regimes, but this requires an understanding of the relationship between plasticity and directional selection for both modified and ancestral populations.