NCBI ROFL: You know what they say about barnacles with long legs...

Modular phenotypic plasticity: divergent responses of barnacle penis and feeding leg form to variation in density and wave-exposure. "Traits can evolve both in response to direct selection and in response to indirect selection on other linked traits. Although the evolutionary significance of coupled traits (e.g., through shared components of developmental pathways, or through competition for shared developmental resources) is now well accepted, we know comparatively little about how developmental coupling may restrict the independent responses of two or more phenotypically plastic traits in response to conflicting environmental cues. Such studies are important because coupled development, if present, could act as an important limit to the evolution of functionally independent plasticity in multiple traits. I tested whether developmental coupling can restrict the direction of plastic responses by studying how penis form and leg form-both highly plastic traits of barnacles-varied in response to differences in conspecific density and water velocity. Penis length ...