SEX AND THE DYNAMICS OF INFECTION IN THE ENTOMOPATHOGENIC NEMATODE STEINERNEMA-FELTIAE

An infection experiment was conducted to assess the change in the prop ortions of Steinernema feltiae Filipjev (Site 76 strain) infective juv eniles becoming male or female on exposure to the test host Galleria m ellonella L. Using a mathematical model for the infection interaction, the per capita probability of penetration per unit time (transmission coefficient), for those juveniles becoming male or female, and the ma gnitude of the male and female classes in the infective juvenile pool were estimated. The results show that S. feltiae infective juveniles w hich subsequently become female have a greater probability of invasion into test hosts than their male counterparts, which leads to markedly female biased sex ratios during the initial stages of the infection i nteraction. As the infection progresses, however, it was found that th e sex ratio became balanced. This was because the underlying sex ratio in the infective stage pool was balanced. The implications of this dy namism in the sex ratio of the entomopathogenic nematodes are discusse d with respect to the infection interaction, transmission and the like ly environment in which the infective juveniles reside.