UC Irvine

Successful foraging is crucial to the energetic demands of fishes, but the role of lateral-line system during feeding remains unclear. In this dissertation I investigated how the lateral line mediates foraging throughout ontogeny of zebrafish. The results demonstrate the fish need the lateral-line system to successfully feed in the dark, and the types of lateral-line receptors play an important role during foraging.

My first chapter developed a series of lateral-line manipulations to test how flow receptors influences foraging success. I also examined the morphology of the receptors to determine if morphological changes in the receptors during early growth may improve flow sensitivity. The results suggest that the lateral line is not important when foraging in light, but in the dark, that lateral line is necessary. In addition, the receptors do not increase in size or numbers during early growth to explain improved sensitivity during growth, however, experiences to flows throughout development suggests that fish learn to forage on prey in 15-day old larvae.

In my second chapter, I investigated how zebrafish respond to various frequencies of oscillating flow in the dark created by an artificial stimulus resembling prey. I compared the bite attempts of fish with different lateral line profiles, presence or absence of receptors, to determine if growth enhances the ability of fish to detect flows in the dark. This improvement was greater at high oscillating-frequencies (above 50 Hz), compared to those below 50 Hz, suggesting that canal neuromasts, which develop in adults, improve foraging in the dark.

I modeled the sensitivity of the lateral-line receptors exposed to flows generated by the artificial stimulus in chapter three. A biophysical model predicting neuromast sensitivity was evaluated with the parameters of flows and zebrafish used in chapter 2. The flows generated by stimuli were measured using a novel digital partial image-velocimetry technique to determine which flows fish responded to in the dark. The biophysical model and flows suggest that fish respond best with the canal neuromasts, and the lateral line receptors exist as a network allowing fish to detect flows at great distances.