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SUMMARY:Continuous spectrum of gaits controlled by mechanical stress in C.
  elegans - Félix Lebois - Laboratoire Matière et Systèmes Complexes (MS
 C)\, Université Paris Diderot
DTSTART:20101217T110000Z
DTEND:20101217T120000Z
UID:TALK28469@talks.cam.ac.uk
CONTACT:Alexandre Kabla
DESCRIPTION:C. elegans is a small (1mm long) worm living in the soil\, and
  extensively studied as a model organism for molecular biology and neurosc
 ience. It relies on undulatory locomotion to move through its natural habi
 tat: a wave of muscular contraction propagates from the head to the tail\,
  thus pushing the worm forward. Two examples of locomotion have been descr
 ibed in the laboratory. The worm crawls on the surface of agar gels\, wher
 e capillary forces constrain it to a bi-dimensional plane. In water the wo
 rm swims\, with a Reynolds number close to 1. These two locomotion modes a
 re characterized by distinct body shapes and bending frequencies. It remai
 ns unclear whether these two modes are the modulation of a single locomoti
 on mechanism or rather the expression of different patterns of neural exci
 tation.\n\nTo investigate the transition from crawling to swimming\, we de
 signed an original experimental set-up. A worm\, immersed in a liquid\, is
  gradually confined between an agar gel and a glass plate. We are thus abl
 e to observe a continuous evolution of the locomotion gait from free swimm
 ing to crawling as the degree of confinement is increased. The evolution o
 f the measured bending frequency\, wavelength and body curvature of the wo
 rm displays no discontinuity in the wild-type nematode as the confinement 
 is varied. Swimming and crawling thus simply result from the modulation of
  a single gait. Additional experiments\, where a crawling worm is suddenly
  released by lifting up the glass plate indicate that this modulation is s
 mooth and does not require an adaptation time when the environment changes
 . The use of mutants provides some additional clues about the neural and m
 olecular mechanisms behind this modulation: the regulation of the locomoti
 on in response to changes in the mechanical environment might rely on the 
 integration of external signaling as well as proprioception.
LOCATION:Engineering Department - Small Oatley Meeting Room
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