Density-dependent sex-biased development of macroptery in a water strider

Photoperiod controls wing polyphenism in a water strider independently of insulin receptor signalling

Insect wing polyphenism has evolved as an adaptation to changing environments and a growing body of research suggests that the nutrient-sensing insulin receptor signalling pathway is a hot spot for the evolution of polyphenisms, as it provides a direct link between growth and available nutrients in the environment. However, little is known about the potential role of insulin receptor signalling in polyphenisms which are controlled by seasonal variation in photoperiod. Here, we demonstrate that wing length polyphenism in the water strider Gerris buenoi is determined by photoperiod and nymphal density, but is not directly affected by nutrient availability. Exposure to a long-day photoperiod is highly inducive of the short-winged morph whereas high nymphal densities moderately promote the development of long wings. Using RNA interference we demonstrate that, unlike in several other species where wing polyphenism is controlled by nutrition, there is no detectable role of insulin receptor signalling in wing morph induction. Our results indicate that the multitude of possible cues that trigger wing polyphenism can be mediated through different genetic pathways and that there are multiple genetic origins to wing polyphenism in insects.

Genomics of the semi-aquatic bugs (Heteroptera; Gerromorpha): recent advances toward establishing a model lineage for the study of phenotypic evolution

Gerromorpha, also known as semi-aquatic bugs, present the striking capability to walk on water surface, which has long attracted the interest of many scientists. Yet our understanding of the mechanisms associated with their adaptation and diversification within this new habitat remain largely unknown. In this review we discuss how new transcriptomic and genomic resources have contributed to establish the Gerromorpha as an important lineage to study phenotypic evolution. In particular we outline the impact of recent comparative transcriptomic analyses and first published genomes to advance our understanding of genomic basis of adaptations to water surface locomotion and sexual dimorphism.