Unexpected Parallels Between Insects and Mammals
For decades biologists drew a clear line: mammals savor flavors, insects merely react. Recent experiments conducted by Southern Medical University in Guangzhou and Macquarie University in Sydney challenge that divide. By filming bumblebees in slow motion, researchers observed a striking licking motion after the insects sipped sugary water—a behavior reminiscent of how mammals lick their lips after tasting something pleasant.
How the Test Was Set Up
Eighteen bumblebee colonies were presented with a sequence of droplets ranging from highly concentrated sugar solution to weak sugar, plain water, salty water, and bitter quinine solution. When a bee finished a sugary droplet, it repeatedly extended and retracted a tongue‑like organ called the glossa, especially with the stronger solution. By contrast, the same bees either ignored plain water or made vigorous head shakes and foreleg wipes when presented with salty or bitter liquids.
Beyond Reflex: Motivation vs. Pleasure
To determine whether the licking was a simple reflex or an expression of enjoyment, the scientists manipulated the bees' internal states. When the insects were heated to 40 °C until they became lethargic, they began to accept water and salty solutions and displayed the same licking pattern afterward—mirroring how thirsty rats will suddenly find salty water palatable when they suffer from a sodium deficit. This shows that the response hinges on physiological need rather than a static chemical trigger.
Further experiments separated “wanting” (the drive to obtain a fluid) from “liking” (the hedonic assessment). By mixing sugar with salt, bees still drank the mixture, yet the post‑drink licking dramatically declined. Even when the final droplet was fully consumed, the licking response was minimal, indicating that the motivation to drink persisted while the pleasure signal evaporated. This dissociation mirrors classic mammalian studies where dopamine fuels the desire to eat, whereas endocannabinoids like anandamide modulate the feeling of enjoyment.
Neurochemical Insights
Pharmacological tests reinforced the parallel. Boosting dopamine’s insect counterpart, octopamine, heightened the bees’ eagerness for sugar but left the licking unchanged. In contrast, applying anandamide—a molecule that partakes in mammalian reward pathways—increased the licking frequency. This suggests that the bumblebee’s “liking” circuitry engages mechanisms comparable to those identified in vertebrates.
What This Means for Insect Cognition
The authors stop short of claiming conscious pleasure in bumblebees, yet their findings provide quantifiable, repeatable evidence that these insects exhibit a behavioral pattern indistinguishable from the mammalian “liking” response in timing, chemistry, and form. If taste enjoyment can be parsed in insects, the evolutionary roots of reward may run much deeper than previously thought.
These insights open doors to new comparative studies, potentially reshaping how we view insect sentience, pollinator health, and the broader principles governing taste perception across the animal kingdom.
Source: https://scientias.nl/onderzoek-onthult-opmerkelijke-overeenkomst-tussen-hommels-en-zoogdieren/
