Gene Activity May Help Explain Why Some Ants Rescue Trapped Nestmates

Some worker ants respond to a nestmate in trouble by trying to free it, while others approach without attempting a rescue. A new study suggests that the difference may be linked to gene activity in the ants’ nervous systems rather than to their size, body structure or available energy. Researchers from Johannes Gutenberg University Mainz and Tel Aviv University studied workers of the desert ant species Cataglyphis niger. In laboratory tests, one ant was restrained on the floor of a sand-lined chamber before another worker from the same colony was introduced. The researchers observed each encounter for 15 minutes. They classified an ant as a rescuer if it pulled at the restrained nestmate or dug around it. Ants that approached but did not try to release the trapped worker were categorized as non-helpers. Similar actions are seen when these ants attempt to uncover nestmates buried in sand, according to the research report. The team then examined RNA from the ants’ antennae and several brain regions, including the optic lobes and mushroom bodies. Mushroom bodies are central processing areas in insect brains that integrate sensory information and are involved in learning and behavioral control. The clearest differences appeared in the mushroom bodies. Fifteen genes were more active in rescuing ants in that tissue, including genes associated with odor detection, hormonal regulation, metabolism and immune functions. Across all the tissues examined, the researchers identified nine genes that were more active in rescuers than in non-rescuers. The findings offered no evidence that rescuing ants were simply stronger or better supplied with energy. Instead, the researchers said differences in how sensory signals are processed, along with molecular signaling pathways, may affect whether an ant reacts to a nestmate in danger. The study also highlighted immune-related genes. Earlier research has linked such genes in insects not only to defense against pathogens but also to activity, sleep and social behavior. The researchers said immune activity might help regulate social responses, although rescuing ants could also face greater risks of injury or infection during these encounters. Published in the Journal of Experimental Biology, the study does not establish one cause of rescue behavior. The researchers describe helping as a likely result of several interacting processes, including detecting distress signals, processing them in the nervous system and regulating the readiness to respond.