Student Theses and Dissertations

Date of Award

2011

Document Type

Thesis

RU Laboratory

Hudspeth Laboratory

Keywords

Aplocheilus lineatus, sensory stimuli, sensory antenna, ridges, lateral line, superficial neuromasts

Abstract

The perception of sensory stimuli by an animal requires several steps, commencing with the capture of stimulus energy by an antenna. As the interface between the physical world and sensory transduction, the antenna modifies the stimulus in ways that enhance the animal’s perception. For example, the mammalian external ear collects sound and spectrally alters it to increase sensitivity and improve the detection of directionality. The surfacefeeding killifish Aplocheilus lineatus is able to hunt in darkness by detecting surface capillary waves with the lateral-line system atop its head. This cephalic lateral line consists of 18 stereotyped mechanosensitive neuromasts, each bordered by fleshy ridges. Each neuromast has a single axis of sensitivity along its longitudinal axis. The ridges bordering each neuromast form a channel parallel to the neuromast’s axis of sensitivity. The ridges direct water oscillations along the length of the channel and are able to block the transmission of surface waves. The neuromasts respond to stimulation ranging from tens of hertz to hundreds of hertz at amplitudes from tens of nanometers to a few micrometers peak-to-peak. Each neuromast has a unique receptive field defined by its directional sensitivity to stimulation of the water surface. The receptive field is sharply modulated in angle, which cannot be explained either by changes in response to angle of the waves on the surface of the water or by the angular sensitivity of the hair cells within the neuromast. Instead, the receptive field is determined by the ridges altering the flow of water over and around each neuromast. Modification of the hydrodynamic environment by the addition of a supplemental ridge perturbs the receptive fields of adjacent neuromasts and affects the transmission of waves over the head. We found that the addition of a supplemental ridge inhibits the fish’s behavioral performance by significantly increasing both the fish’s reaction time to a stimulus and the probability that it fails to respond to a stimulus. We propose that the ridges constitute a hydrodynamic antenna for the cephalic lateral line of Aplocheilus lineatus.

Comments

A thesis presented to the faculty of The Rockefeller University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

Permanent URL

http://hdl.handle.net/10209/394

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