  Pareatic snakes possess outstanding asymmetry in the mandibular tooth number,
which has probably been caused by its evolution to improve the feeding on the
predominant dextral snails. Gene mutation can generate chiral inversion on the
snail body. A sinistral snail population can thrive in this ecological context.
The interactions between dextral/sinistral snails and Pareas snakes are modeled
in this paper by using a new generalized functional response of Holling type
II. Distinct Pareas species show different bilateral asymmetry degrees. This
parameter plays an essential role in our model and determines the evolution of
the populations. Stability of the solutions is also analyzed for different
regimes in the space of parameters.
