Reduction of brain volume correlates with behavioral changes in queen ants

Area of Science:

• Entomology
• Neurobiology
• Animal Behavior

Background:

• Reproductive female ants undergo significant behavioral and morphological changes transitioning from virgin to mature queens.
• This transition is marked by a single nuptial flight, wing shedding, nest excavation, and the commencement of egg-laying.

Purpose of the Study:

• To investigate the behavioral and neural changes accompanying the transition from virgin to mature queen in two harvester ant species.
• To determine if observed brain morphology changes correlate with behavioral shifts and reproductive status.

Main Methods:

• Comparative behavioral assays measuring phototaxis and area preference in virgin and mature queens.
• Morphological analysis of brain structures, focusing on visual system components, in both reproductive ant castes.

Main Results:

• Virgin ants exhibited positive phototaxis and preferred open areas, while newly mated queens showed negative phototaxis, preferred darkness, and initiated digging behaviors.
• Mature queens possessed significantly smaller brains compared to virgin females, with notable reductions in the medulla and visual processing areas.
• Behavioral repertoire was reduced in mature queens, correlating with decreased reliance on vision.

Conclusions:

• The transition to a mature queen ant involves adaptive neural reorganization, including brain size reduction, particularly in visual processing centers.
• These changes facilitate a shift towards a subterranean, dark-dwelling lifestyle, optimizing energy allocation and reproductive success.