Intrinsic and extrinsic drivers of hypometabolic states in insects
06 Nov 2025 - Philipp Lehmann, University of Greifswald| 10h30 | Hybrid Seminar
CASUAL SEMINAR IN BIODIVERSITY AND EVOLUTION
Diapause is a deep resting stage that facilitates temporal avoidance of unfavourable environmental conditions, and is used by many insects to adapt their life cycle to seasonal variation. Although considerable work has been invested in trying to understand each of the major diapause stages, we know very little about the extrinsic and intrinsic drivers of transitions between stages, especially diapause termination. Here I will present three studies using pupae of the butterfly Pieris napi. (1) In this species, diapause is associated with both temperature-dependent and -independent processes. While the general diapause phenotype is established in a temperature-independent fashion, diapause termination is temperature-dependent and requires a cold signal. (2) The shape of cold-accumulation follows a unimodal nonlinear thermal reaction norm, with optimal rates at winter temperatures. We model this reaction norm as a mirrored version of a typical thermal performance curve and use it to successfully predict diapause termination in multiple fluctuating laboratory temperatures. (3) A putative underlying physiological mechanism of thermal accumulation involves the key developmental hormones prothoracicotropic hormone (PTTH) and ecdysone, whose temperature-dependence we have studied and manipulated during diapause. While PTTH is present throughout diapause in two pairs of neurosecretory cells in the brain, it is absent in the axons and PTTH concentration in the haemolymph is significantly lower during diapause than during post diapause development, indicating that the PTTH pathway is silenced during diapause. At low temperatures, reflecting natural overwintering conditions, diapause termination propensity after ecdysone injection is precocious compared to controls. The link between ecdysone sensitivity and low -temperature dependence reveals a putative mechanism of how diapause termination operates in insects that is in line with adaptive expectations for diapause.
Philipp Lehmann received his MSc in Physiology from Helsinki University, Finland, in 2009, and subsequently did his PhD in Ecology and Evolutionary Biology at Jyväskylä University, Finland, graduating in 2013. He then moved for a postdoctoral fellowship to the University of Stockholm, Sweden, in 2014. After a short research visit to Stellenbosch, South Africa, he started his own group, funded by the Swedish Research councils VR and Formas, in Stockholm in 2018. In 2021, he took up the professorial chair in animal physiology at the University of Greifswald, Germany. He also maintains a position in Stockholm as associated researcher. Lehmann is an ecophysiologist with broad interests, but his main research focus is animal adaptations to seasonal environments, with emphasis on bioenergetics and biological timing mechanisms. He mostly works with insects and hypometabolic adaptations but is also interested in how endo- and heterothermic animals such as mammals are able to plastically adjust metabolic performance.
[Host: Zbyszek Boratynski, Biodiversity of Deserts and Arid Regions - BIODESERTS]
Zoom Link (Passcode: 332211)
Zoom Link (Passcode: 332211)