Zfish Research

Laboratory of Comparative Neurobiology
Dalhousie University, Department of Physiology and Biophysics
Sir Charles Tupper Medical Building, Halifax, Nova Scotia, Canada, B3H 1X5

Dalhousie University

Zebrafish Research
	Swimbladder development and buoyancy control in the zebrafish. We use the zebrafish to investigate the development of buoyancy control in the swimbladder from the time of first inflation to adulthood. Proper development of the swimbladder in the zebrafish and many other teleost fishes is crucial for the survival and ethology of these animals. The swimbladder plays a central role in depth regulation in the water column, as well as to maintain neutral buoyancy to reduce energy expended by swimming. By taking advantage of the transparency of larval zebrafish we are able to observe morphological changes in swimbladder anatomy from when this organ first develops as an outpocketing of the gut, to its final adult, double-chambered form. Using a combination of behavioural assays, morphometric analyses, and pressure changes experiments to simulate variations in swimming depth in the water column, this work will provide a better understanding of the contribution of the swimbladder to buoyancy regulation. Principal Researcher: Benjamin Lindsey

	The effect of the compliance of the swimbladder wall on buoyancy and hearing function in the zebrafish. The zebrafish (Danio rerio), as with any fish, must maintain neutral buoyancy within the water in which it swims to reduce related energetic costs. In the adult zebrafish this is accomplished via a gas-filled, double-chambered swimbladder, which acts as both an acoustic resonator and buoyancy control organ. Changes from atmospheric pressure act differently on the two chambers with the anterior chamber having greater compliance and response to pressure changes. Composition differences between the two chambers, allows for differential changes in the expansion and contraction of the swimbladder walls in response to simulated changes in depth. As a result, changes in swimbladder chamber conformation affect animal density and shift the center of buoyancy. In the zebrafish the anterior chamber has also been shown to allow perception of acoustic signals over a broad frequency range. As a result of the observed compliance and volumetric differences in the anterior chamber a deficit in hearing may result due to altered swimbladder resonance abilities. Principal Researcher: Matthew Stoyek

	Chemosensory processing and its modifications through learning in zebrafish. I am interested in the neurobiology and behavior of zebrafish chemosensation. This animal is particularly useful for such studies as it permits us to link the activity of individual neurons with whole animal behavior. I have recently developed a novel behavioral assay that allows us to study chemosensory behaviors in zebrafish of varying ages. Using this assay, I have also been able to train zebrafish to associate various odorants (conditioned stimuli) with the event and location of food rewards (unconditioned stimuli). This has led to robust changes in their innate response to odorants, and I am currently studying how such learned behaviors are represented in the olfactory system; i am using various anatomical, physiological and genetic techniques to map regions of the olfactory bulb that are modified by learning and ultimately I hope to study synaptic plasticity in the zebrafish olfactory system in vivo. Principal Researcher: Oliver Braubach

	Swimbladder physiology in the zebrafish. The zebrafish swimbladder is unique in that it is a simple organ which we can use to study complex physiological processes. The autonomic neurological control of organs is poorly understood in vertebrates, and this air-filled evagination of the gut is a good model for these processes. Using pharmacology and electrophysiology, we will attempt to identify neurochemicals released from the neurons that innervate the organ as well as the receptor substrates found on the post-synaptic effectors. The effects of the traditional autonomic neurotransmitters norepinephrine and acetylcholine, as well as peptides, amines and amino acids recently localized to the swimbladder will all be analyzed using agonists and antagonists. Changes in blood vessel caliber, blood flow and smooth muscle contraction will all be examined as indices of swimbladder volume change in response to neurochemicals. Principal Researcher: Tristan Dumbarton

	The effect of exposure of zebrafish to simulated microgravity on swimbladder anatomy, physiology and whole animal behaviour. Exposure to microgravity and hypergravity conditions results in changes in the vestibular system and normal behaviour of fish, amphibians, reptiles and mammals during space missions, parabolic flights or centrifugation. In the zebrafish recent work by Stephen Moorman has shown that both the vestibular anatomy (saccular and utricular otoliths) and normal behaviour of larvae are disrupted following exposure to simulated microgravity. To examine changes in swimbladder anatomy, physiology and whole animal behaviour, we make use of a bioreactor created by NASA. The bioreactor functions by maintaining eggs or larvae in a circular orbit, thus approximating a gravitational force near zero. Following exposure to simulated mcrogravity we apply a combination of techniques including immunohistochemistry, physiology, pharmacology, morphometrics and behavioural assays, to compare the response of larvae exposed microgravity conditions with age-matched controls. We are interested in the effects of short exposure times to simulated microgravity at two critical stages of swimbladder development: first inflation, and during maturation of the second (posterior) chamber of the swimbladder. This work is funded by the Canadian Space Agency. Principal Researchers: Benjamin Lindsey and Tristan Dumbarton

	Olfactory learning in the zebrafish. My interests include animal cognition, learning and memory. I am currently training adult zebrafish to discriminate between various amino acid and synthetic odorants in an olfactory learning paradigm. I hope to train larval zebrafish in the same type of task, perhaps uncovering the age at which this ability develops. Principal Researcher: Heather-Dawn Wood

	The characterisation of the anatomy of barbels in the adult zebrafish. We are studying the anatomy and development of the gustatory system in zebrafish. As in other fish, this system is spread virtually all over the fish's body, with few specialized areas such as the barbels and oral cavity. We are currently focusing on the anatomy and distribution of taste cells within these specialized areas and are also outlining their innervation by the nervous system. Future research will examine how this system is involved in the reception and coding of chemosensory stimuli, and how information about gustatory stimuli and olfactory stimuli converge in the brain. Principal Researcher: Oliver Braubach Researchers: Isela-Hernandez Plata, Lesley Roberts