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Updated: Sep 28, 2026
Circadian Entrainment of Drosophila Melanogaster
Published on: June 3, 2020
Mushroom body influence on locomotor activity and circadian rhythms in Drosophila melanogaster
Charlotte Helfrich-Förster1, Jörg Wulf, J Steven de Belle
1Max-Planck-Institut für Biologische Kybernetik, Spemannstrasse 38, D-72076 Tübingen, Germany.
Abstract:
Whether or not mechanisms underlying circadian locomotor rhythms and learning are related anatomically through the mushroom bodies (MBs) was investigated by monitoring behavioral rhythmicity in flies with MB lesions induced by chemical ablation and by mutations in five different genes. All flies tested were later examined histologically to assess (1) MB neuroanatomy, and (2) the condition of the putative pacemaker cells--the ventral Lateral Neurons (LN(v)s) and their terminals that project to the vicinity of the MB calyces. All groups of flies had normal rhythms except for mushroom body miniature (mbm; only in a wild-type Berlin genetic background) and mushroom body defect (mud). MB ablation had no effect on the gender-specific differences in the rhythmic activity profile that are typical of wild-type flies. However, ablated males had a slightly longer period than untreated males and were more active under constant dark conditions. LN(v)s and their arborization patterns appeared normal in MB-ablated and in most mutant flies. Activity defects of mbm flies were attributed to genetic background rather than to the mutation alone. Misrouted LN(v) projections and approximately 14% arrhythmia of mud flies were uncorrelated and attributed to pleiotropy rather than to specific effects of MB lesions. Our results imply that MBs are not involved in circadian activity rhythms but that they do have an inhibitory effect on activity levels of male flies.
Insights
The mushroom bodies (MBs) in flies are not involved in circadian rhythms. However, MB lesions in male flies showed an inhibitory effect on activity levels, suggesting a role in regulating arousal.
Area of Science:
- Neuroscience
- Chronobiology
- Animal Behavior
Background:
- Circadian rhythms and learning mechanisms are crucial for organismal survival.
- The mushroom bodies (MBs) are key brain structures in insects, known for their roles in learning and memory.
- The potential anatomical link between MBs and circadian locomotor rhythms remains largely unexplored.
Purpose of the Study:
- To investigate the anatomical relationship between mushroom bodies (MBs) and the neural mechanisms governing circadian locomotor rhythms in flies.
- To determine if MB lesions affect circadian rhythmicity and associated behaviors.
Main Methods:
- Induction of MB lesions using chemical ablation and genetic mutations in five different genes.
- Monitoring of behavioral rhythmicity in genetically modified flies.
- Histological examination of MB neuroanatomy and ventral lateral neurons (LN(v)s).
Main Results:
- Mushroom body lesions did not affect circadian rhythmicity in most tested flies.
- MB ablation did not alter typical gender-specific differences in activity profiles.
- Ablated male flies exhibited a slightly longer period and increased activity under constant dark conditions.
- LN(v)s and their projections appeared normal in most MB-ablated and mutant flies, with exceptions noted for specific mutations.
Conclusions:
- Mushroom bodies are not intrinsically involved in the generation or maintenance of circadian locomotor rhythms.
- MBs exert an inhibitory influence on the overall activity levels in male flies.
- Observed activity defects in certain mutants were attributed to genetic background or pleiotropy, not direct MB-circadian rhythm interactions.
