Cold Temperatures Increase Neural Connections in Fly Brains
Lower temperatures during development increase neural connections in fruit flies, altering brain wiring.
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The development of poikilothermic animals – such as insects, reptiles and fish – is largely dictated by temperature. A new study from Johannes Gutenberg University Mainz (JGU) has demonstrated that temperature during early development influences brain connectivity in fruit flies (Drosophila melanogaster), with lower temperatures leading to the formation of more neural connections.
Poikilothermic animals
Organisms whose body temperature fluctuates with environmental conditions. Unlike mammals and birds, these animals lack internal mechanisms to regulate body heat.
Focusing on the olfactory circuit, researchers found that fruit flies raised at 18 degrees Celsius during the pupal stage developed more than twice as many postsynaptic neurons in certain brain regions compared to those raised at 25 degrees Celsius. Since the sense of smell is critical for the survival of these insects, understanding how environmental conditions affect their neural wiring could provide insight into broader ecological and developmental processes.
Synapse
A junction between two nerve cells where electrical or chemical signals are transmitted. Synapses enable communication between neurons and are essential for brain function and behavior.
Olfactory circuit
A neural network responsible for processing odors. In fruit flies, as in other animals, the olfactory system plays a key role in detecting environmental cues and guiding behavior.
A metabolic perspective on brain development
Temperature plays a key role in regulating metabolic rates, which in turn influence the rate of biological processes. Previous studies have shown that temperature affects synapse formation in the Drosophila visual system, but the new research expands this understanding to the olfactory system.
Metabolism
The set of biochemical reactions that sustain life, including energy production and cell growth. Metabolic rates influence how quickly organisms develop and respond to environmental changes.The team proposed that differences in metabolic activity between neurons and other body cells might explain the increase in synaptic connections at lower temperatures. Specifically, they hypothesized that brain metabolism remains relatively high even at reduced temperatures, leading to prolonged neural development compared to the rest of the body. Ongoing experiments examining gene expression during development aim to further test this hypothesis.
Changes in behavior linked to developmental temperature
The impact of temperature extended beyond brain structure, influencing odor-driven behavior in adult flies. Flies that developed at the lower temperature showed a stronger attraction to butanone, a pungent-smelling chemical, compared to those raised at 25 degrees Celsius.
Despite increased neural connectivity, the researchers found no change in odor perception at the level of primary sensory processing. This suggests that the observed behavioral differences may stem from changes in brain regions responsible for processing and integrating sensory information, rather than from heightened sensory detection.
By investigating how temperature shapes neural circuitry and behavior, this study offers valuable insight into the developmental plasticity of poikilothermic animals and the potential effects of environmental changes on species with temperature-dependent growth patterns.
Reference: Züfle P, Batista LL, Brandão SC, D’Uva G, Daniel C, Martelli C. Impact of developmental temperature on neural growth, connectivity, and function. Sci Adv. 2025;11(3):eadp9587. doi: 10.1126/sciadv.adp9587
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