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Weissburg, Marc J.

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Author: Fields, David M. ×

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    Chemoreception in the salmon louse (Lepeophtheirus salmonis): an electrophysiology approach
    (Georgia Institute of Technology, 2007-12-13) Fields, David M. ; Weissburg, Marc J. ; Browman, H. I.
    The search for effective and long-term solutions to the problems caused by salmon lice Lepeophtheirus salmonis (Krøyer, 1837) has increasingly included biological/ecological mechanisms to combat infestation. One aspect of this work focuses on the host-associated stimuli that parasites use to locate and discriminate a compatible host. In this study we used electrophysiological recordings made directly from the antennule of adult lice to investigate the chemosensitivity of L salmonis to putative chemical attractants from fish flesh, prepared by soaking whole fish tissue in seawater. There was a clear physiological response to whole fish extract (WFX) with threshold sensitivity at a dilution of 10–4. When WFX was size fractionated, L. salmonis showed the greatest responses to the water-soluble fractions containing compounds between 1 and 10 kDa. The results suggest that the low molecular weight, water-soluble compounds found in salmon flesh may be important in salmon lice host choice.
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    Evolutionary and ecological significance of mechanosenor morphology: copepods as a model system
    (Georgia Institute of Technology, 2005-02-18) Fields, David M. ; Weissburg, Marc J.
    The ability to sense fluid motion is strongly influenced by morphological properties of setae and by the way in which they are organized into an ensemble along the mechanosensory organ (i.e. the antennule). Setal length and orientation affect how setae encode basic properties such as velocity, frequency and direction, whereas the arraignment of setae mediate perception of more complicated properties, such as shear. Morphological and physiological data indicate that the design of setae and antennules bias an organism towards detecting particular types of disturbances, or for efficient operation in certain environments. These structure-function relationships provide potential insight into trophic status, predator detection abilities or distributions, and perhaps can explain the fantastic degree of variation in setal morphology. However, structure-function predictions remain largely unverified, because we generally lack complementary data on both the design and ecological roles of the mechanosensory system in a particular organism. Thus, an important challenge is to use a comparative approach to determine whether design principles of mechanosensory systems can explain organismal properties, and therefore provide insights into ecological interactions in the plankton.
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    Mechanical and neural responses from the mechanosensory hairs on the antennule of Gaussia princeps
    (Georgia Institute of Technology, 2002-02-13) Fields, David M. ; Shaeffer, D. S. ; Weissburg, Marc J.
    This study investigated the physical and physiological response of individual setae on the antennule of Gaussia princeps. We found significant differences in the physical and physiological responses of the setae to various intensities of water flow. No physiological evidence was found to suggest that individual setae are dually innervated; however, directional bias in both the displacement and subsequent physiological responses was evident. Although more easily displaced by fluid flow, the shortest hairs were physiologically less sensitive to angular deflection than were the longer setae, so that slow flows produced a greater neural response in the long seta. The combination of high resistance to movement and acute physiological sensitivity allows the long seta to respond to biologically driven, low-intensity flows while filtering out high-frequency background noise. This suggests that the most prominent, long, distal setae function as low-flow detectors whereas the short hairs respond to more rapid fluid motion. Each seta responds to only a portion of the overall range of water velocity in the copepod's habitat. Thus, the entire sensory appendage, which consists of an ensemble of setae of different morphologies and lengths, may function as a unit to code the intensity and directionality of complex fluid disturbances.