Biology subjects

Thamm, M.

Publications and source records attributed to Thamm, M..

5 recordsLinked to original sources

bioRxiv2024

Variability in honey bee cuticular hydrocarbon composition can be understood as a function of gene expression

Most terrestrial insects have a layer of cuticular hydrocarbons (CHCs) protecting them from desiccation and mediating chemical communication. CHC composition is regulated by the expression of genes coding for enzymes in the biosynthetic pathway of hydrocarbons. The diversity and expression of these enzymes determine the abundance and richness of compounds in the CHC profile of an insect. For example, elongases are enzymes that lengthen the hydrocarbon chain, while desaturases introduce double bonds in it. CHC profiles of honey bees (Apis mellifera) vary among castes, task groups, and subspecies. This makes A. mellifera an excellent model to study the molecular mechanism underlying CHC biosynthesis. Here, we examined the expression of specific elongase- and desaturase-encoding genes and correlated gene expression with CHC composition in bees from two different task groups of two highly divergent A. mellifera subspecies: A. m. carnica and A. m. iberiensis. We show that in A. mellifera, the specificity of desaturases and elongases shapes the CHC profiles of different task groups. Our results shed light on the genetic basis for the task-specific CHC composition differences in social hymenopterans and lay the ground for further studies aiming to unravel the genetic underpinning of CHC biosynthesis. Moreover, these results underline the importance of investigating different subspecies of A. mellifera to better understand the mechanisms driving CHC composition.

ecology↗

bioRxiv2022

Walking bumblebees see faster

The behavioral state of an animal has profound effects on neuronal information processing. Locomotion changes the response properties of visual interneurons in the insect brain, but it is still unknown if it also alters the response properties of photoreceptors. Photoreceptor responses become faster at higher temperatures. It has therefore been suggested that thermoregulation in bees and other insects could improve temporal resolution in vision, but direct evidence for this idea has so far been missing. Here we compared electroretinograms (ERGs) from the compound eyes of tethered bumblebees that were either sitting still or were walking on an air supported ball. We found that the visual processing speed strongly increased when the bumblebees were walking. By monitoring the bumblebees eye temperature during our recordings, we saw that the increase in response speed was in synchrony with a rise of the eye temperature. By artificially heating the bees head, we show that the walking induced temperature increase of the visual system is sufficient to explain the rise in processing speed. We also show that walking accelerates the visual system to the equivalent of a 14-fold increase in light intensity. We conclude that the walking-induced rise in temperature accelerates the processing of visual information in bumblebees, which is an ideal strategy to process the increased information flow during locomotion.

neuroscience↗

bioRxiv2022

Robustness of the neuro-muscular octopaminergic system in the face of cold stress.

In recent decades, our planet has undergone dramatic environmental changes resulting in the loss of numerous species. This contrasts with species that can adapt quickly to rapidly changing ambient conditions, which require physiological plasticity and must occur rapidly. The Western honeybee (Apis mellifera) apparently meets this challenge with remarkable success, as this species is adapted to numerous climates, resulting in an almost worldwide distribution. Here, coordinated individual thermoregulatory activities ensure survival at the colony level and thus the transmission of genetic material. Recently, we showed that shivering thermogenesis, which is critical for honeybee thermoregulation, depends on octopamine signaling. In this study, we tested the hypothesis that the thoracic neuro-muscular octopaminergic system strives for a steady-state equilibrium under cold stress to maintain endogenous thermogenesis. We can show that this applies for both, octopamine provision by flight muscle innervating neurons and octopamine receptor expression in the flight muscles. Additionally, we discovered alternative splicing for AmOAR{beta}2 and our results suggest that at least one isoform is needed to survive cold stress conditions. We assume that the thoracic neuro-muscular octopaminergic system is finely tuned in order to contribute decisively to survival in a changing environment.

physiology↗

bioRxiv2021

Intrasexual cuticular hydrocarbon dimorphism in a wasp sheds light on hydrocarbon biosynthesis genes in Hymenoptera

Cuticular hydrocarbons (CHCs) cover the cuticle of insects and serve as desiccation barrier and for chemical communication. While the main enzymatic steps of CHC biosynthesis are well understood, few of the underlying genes have been identified. Here we show how exploitation of intrasexual CHC dimorphism in a mason wasp, Odynerus spinipes, in combination with whole-genome sequencing and comparative transcriptomics facilitated identification of such genes. RNAi-mediated knockdown of twelve candidate gene orthologs in honey bees, Apis mellifera, confirmed nine genes impacting CHC profile composition. Most of them have predicted functions consistent with current knowledge of CHC metabolism. However, we found first-time evidence for a fatty acid amide hydrolase also influencing CHC profile composition. In situ hybridization experiments furthermore suggest trophocytes participating in CHC biosynthesis. Our results set the base for experimental CHC profile manipulation in Hymenoptera and imply that the evolutionary origin of CHC biosynthesis predates the arthropods colonization of land.

molecular biology↗

bioRxiv2021

Octopamine drives honeybee thermogenesis

In times of environmental change species have two options to survive: they either relocate to a new habitat or they adapt to the altered environment. Adaptation requires physiological plasticity and provides a selection benefit. In this regard, the Western honeybee (Apis mellifera) protrudes with its thermoregulatory capabilities, which enables a nearly worldwide distribution. Especially in the cold, shivering thermogenesis enables foraging as well as proper brood development and thus survival. In this study, we present octopamine signaling as a neurochemical prerequisite for honeybee thermogenesis: we were able to induce hypothermia by depleting octopamine in the flight muscles. Additionally, we could restore the ability to increase body temperature by administering octopamine. Thus we conclude, that octopamine is necessary and sufficient for thermogenesis. Moreover, we show that these effects are mediated by {beta} octopamine receptors. The significance of our results is highlighted by the fact the respective receptor genes underlie enormous selective pressure due to adaptation to cold climates. Finally, octopamine signaling in the service of thermogenesis might be a key strategy to survive in a changing environment.

neuroscience↗