Constant illumination reduces circulating melatonin and impairs immune function in the cricket Teleogryllus commodus

Area of Science:

• Environmental Science
• Immunology
• Chronobiology

Background:

• Constant light exposure negatively affects behavior and physiology, notably reducing immune function in diverse taxa.
• Melatonin suppression due to light at night is hypothesized as a key mechanism underlying these immune changes.

Purpose of the Study:

• To investigate the relationship between constant illumination, melatonin levels, and immune function in the Australian black field cricket, Teleogryllus commodus.
• To provide evidence for the impact of artificial light at night on invertebrate physiology.

Main Methods:

• Crickets were reared under a 12h light:12h dark cycle or constant 24h light.
• Haemolymph was analyzed to assess circulating melatonin concentration and immune parameters: haemocyte concentration, lytic activity, and phenoloxidase (PO) activity.

Main Results:

• Constant illumination significantly reduced melatonin concentrations in crickets.
• Reduced haemocyte concentrations and lytic activity were observed under constant light conditions.
• The effect of constant light on phenoloxidase (PO) activity was less pronounced.

Conclusions:

• This study presents the first evidence linking constant illumination to altered haemocyte concentration in an invertebrate model.
• The findings suggest a complex immune response to constant light exposure in invertebrates.
• Further research is needed to determine if ecologically relevant light levels at night impact invertebrate immunity similarly to vertebrates.