Roundworm infections cause several debilitating diseases in both animals and agricultural plants, yet relatively little is known about the factors that regulate either the population dynamics and/or infectivity of most parasitic or free-living nematode species. This proposal aims to uncover the mechanisms by which a specific set of closely related roundworm species regulate the ratio of males, females, and/or infective/dispersive larval forms amongst their offspring. A combination of cellular, chemical and genetic approaches will be used. Broader impacts of the proposal studies include establishing research and student training links between a primarily undergraduate institution (William & Mary) and an institution with a large proportion of minority students (UT-Arlington). In addition, these studies may ultimately lead to new avenues for controlling roundworm infections.