Adult neurogenesis in the mushroom bodies of red flour beetles (Tribolium castaneum, Herbst) is influenced by the olfactory environment

Ernst A Wimmer,Magdalina Schaaf,Stefan Dippel,Björn Trebels,Karthi Balakrishnan,Joachim Schachtner

doi:10.1038/s41598-020-57639-x

Ernst A Wimmer, Magdalina Schaaf + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-57639-x

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Abstract

Several studies showed adult persisting neurogenesis in insects, including the red flour beetle Tribolium castaneum, while it is absent in honeybees, carpenter ants, and vinegar flies. In our study, we focus on cell proliferation in the adult mushroom bodies of T. castaneum. We reliably labelled the progenies of the adult persisting mushroom body neuroblasts and determined the proliferation rate under several olfactory conditions within the first week after adult eclosion. We found at least two phases of Kenyon cell proliferation in the early adult beetle. Our results suggest that the generation of Kenyon cells during the first three days after adult eclosion is mainly genetically predetermined and a continuation of the developmental processes (nature), whereas from day four on proliferation seems to be mainly dependent on the odour environment (nurture). Considering that the mushroom bodies are linked to learning and memory, neurogenesis in the mushroom bodies is part of the remodelling of neuronal circuits leading to the adaption to the environment and optimization of behaviour.

Highlights

IntroductionFollowing development, when the nervous system first encounters environmental sensory input, it is crucial for the survival of an animal to adapt to the actual conditions and cues
The ground pattern of the central nervous system is genetically encoded
We confirmed that in T. castaneum, adult-born Kenyon cells usually derive from two neuroblasts (NB) per hemisphere and send their axons into the core of the mushroom body peduncle (PED) and lobes as shown by Zhao and colleagues[60] (Fig. 1C)

Summary

Introduction

Following development, when the nervous system first encounters environmental sensory input, it is crucial for the survival of an animal to adapt to the actual conditions and cues. The genetically encoded wiring scheme of the nervous system must be altered. This plasticity typically occurs in special time windows of elevated susceptibility to sensory input (critical periods or sensitive phases)[1]. The adult olfactory system of holometabolous insects is first confronted with environmental cues upon adult eclosion. These olfactory cues are mainly detected by the olfactory sensory neurons (OSN) housed in the chemosensory sensilla of the antennae and palps[23,24,25,26]. We concentrated on olfaction which is supposed to be a main input into the mushroom bodies of T. castaneum[26], to answer whether the adult persisting neurogenesis is genetically predetermined and continuation of developmental processes or if it is activity-dependent

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