Hair cell bundle loss as a function of tone frequency and saccule location. Phalloidin-labeled saccular epithelia showing evidence of differential hair cell bundle loss between rostral (A, C) and caudal (B, D) regions in goldfish exposed to 100 (A, B) versus 2000 (C, D) Hz tones. Rostral areas photographed show locations 7-9 (rostral-caudal axis region 3). Caudal areas photographed show regions 11-13 (rostral-caudal axis region 5). Scale bars = 50 μm.