Program of the 2001 International Worm Meeting - Sternberg Lab ...

102
102. Sex Drive in C. elegans
Jonathan Lipton, Scott W. Emmons
Department of Molecular Genetics, Albert
Einstein College of Medicine, Bronx, NY 10461
C. elegans males cultured alone on a bacterial
lawn will not remain indefinitely on the food
source, a behavior we refer to as leaving. We
have analyzed leaving and found that it is a
regulated behavior with characteristics
consistent with the view that it is a
mate-searching behavior. Sexual behaviors such
as mate-searching and copulation are considered
motivated behaviors governed by ill-defined
states of the nervous system known as drive
states. Using a quantitative leaving assay, we
have determined physiological and
environmental variables that influence the
probability of leaving and have isolated both
constitutive and defective leaving mutants.
Thus, we are able to functionally and genetically
dissect an apparent nematode counterpart of sex
drive.
We have found that leaving can be
described as a stochastic process defined by a
probability that differs for males,
hermaphrodites, and juveniles. In a leaving
assay, a single animal is placed in the center of a
small bacterial lawn on a 9cm plate and the
subsequent time interval during which it leaves,
defined as wandering beyond a circle of 3.5cm
radius, is determined. Twenty or more animals
are assayed per experiment and the fraction of
non-leavers as a function of time is plotted.
Leaving can be described by a simple first-order
rate equation characterized by a single
probability of leaving per hour (P L ). In our
assay, P L for adult males is 0.17+/-0.008.
Leaving is both stage- and sex-specific: P L for
adult hermaphrodites is 0.002 and sexually
immature (L4) worms of either sex do not
express appreciable leaving (P L