Neonicotinoids are a widely used class of insecticides designed to target nicotinic acetylcholine receptors (nAChRs) in insects. Although their primary toxicologic target is the insect nervous system, increasing ecological physiology evidence indicates that neonicotinoid exposure can indirectly disrupt whole-organism performance, including thermoregulation. For pollinators such as bumblebees and other Hymenoptera, maintaining an appropriate body temperature is not merely a behavioral trait; it is an essential physiological requirement that gates muscle function, metabolic rate, neural signaling fidelity, digestion, and foraging capacity.
Thermoregulation in bumblebees relies on coordinated heat production and heat exchange. In many bees, flight and targeted behaviors depend on rapid warming of thoracic flight muscles, often supported by shivering thermogenesis and thermal insulation. At the organism level, thermoregulation emerges from the balance between endogenous heat generation and exogenous heat loss driven by ambient temperature, wind, humidity, and body surface properties. When this balance is perturbed, bees may show reduced ability to sustain thoracic temperature during cooling conditions, leading to impaired locomotion, diminished flight duration, and altered foraging efficiency.
Neonicotinoid exposure can impair thermoregulation through several mechanistic pathways. First, nAChR dysregulation can alter excitatory-inhibitory neural control of motor systems, including the neural circuits that coordinate muscle activation rhythms. Even when the bee survives acute exposure, sublethal effects may manifest as inefficient muscle performance, reduced shivering amplitude, or delayed heat generation in response to cooling. Second, neonicotinoids can influence energy allocation by perturbing metabolic regulation. If neural and muscular efficiency decline, metabolic heat output may drop for a given energetic cost, producing a lower steady-state body temperature. Third, stress physiology may exacerbate heat-loss dynamics. Physiological stress responses can increase oxidative load and affect cardiovascular-like hemolymph distribution patterns that support temperature uniformity across tissues.
A key observation in recent pollinator studies is that neonicotinoids impair thermoregulation and lower body temperature under challenging thermal conditions. Notably, these effects are not necessarily uniform across all aspects of physiology; rather, they may specifically reduce the capacity to maintain temperature during cooling or during periods requiring high muscle work. This makes thermoregulation a sensitive integrative endpoint: it reflects how neurotoxic action propagates through muscle function, metabolic heat production, and systemic thermal balance.
Near-infrared (NIR) light has emerged as a potentially relevant modulatory intervention in the context of this phenotype. NIR wavelengths can interact with biological tissues via photophysical and photochemical processes. In broader biomedical literature, NIR light is associated with photobiomodulation, wherein photons can influence mitochondrial function and cellular energy pathways, often described as changes in electron transport chain activity, reactive oxygen species signaling, and downstream modulation of gene expression related to stress and repair. While the exact biophysical mechanism in bees may differ from mammalian models, the conceptual framework is that NIR can partially restore physiological performance by enhancing cellular capacity to generate ATP and regulate stress responses.
Applied to thermoregulation, a plausible explanation is that NIR exposure improves neuromuscular and metabolic efficiency, thereby partially compensating for the heat-generation deficits caused by neonicotinoids. If mitochondrial activity and cellular energetics are improved, bees may regain a fraction of their capacity to produce heat during cooling. Alternatively, NIR could affect peripheral tissue properties or signaling pathways that support muscle activation thresholds, enabling the bee to initiate or sustain thermogenic responses more effectively.
Importantly, the reported effect is partial counteraction rather than complete normalization. This distinction matters clinically and ecologically: pesticide exposure may cause persistent neural receptor-level perturbations that cannot be fully reversed by light-based modulation alone. Nonetheless, even partial restoration of body temperature can have outsized consequences in nature, because small reductions in sustained thoracic temperature can shorten foraging bouts, decrease flight competence, and reduce pollen/nectar collection. From an environmental health perspective, this suggests that thermoregulatory vulnerability is a causal bridge between chemical stressors and downstream population-level outcomes.
The broader implication is that environmental toxicology should consider not only immediate mortality but also integrative physiological endpoints such as thermoregulation. Such endpoints capture the functional consequences of sublethal neurotoxicity and can better predict ecological performance. Future research directions include dose-response characterization, timing of NIR exposure relative to pesticide uptake, and mechanistic studies examining muscle activation dynamics, metabolic markers, and neural electrophysiology. These studies could clarify whether NIR benefits primarily reflect improved energetic throughput, altered stress signaling, or modified tissue responses.
For readers, the key takeaway is that neonicotinoids can impair insect thermoregulation through neuro-muscular and metabolic pathways, leading to reduced ability to maintain body temperature. Near-infrared light exposure appears to partially counter the decline in body temperature, consistent with the idea that photobiomodulation can enhance cellular energetics and physiological resilience. Source: [PeterGraystock]
Peter Graystock: Can light help bees cope with pesticide stress? 🐝 Tianqi from @richjgill lab shows neonicotinoid exposure impairs bumblebee thermoregulation, but near-infrared light exposure can partially counter the decline in body temperature 🚨 #Pollinator #Ecology. #breaking
— @PeterGraystock May 1, 2026
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