(Click here to listen to an audio version of this blog!)
Emotions are hard to quantify and have been a difficult area of research in non-human subjects. Long standing cautions against anthropomorphic explanations or descriptions in animal behavior studies have only recently been modified in large part due to pioneering behavioral studies on several of our most closely related primate species. As Frans de Waal put it in his July 1997 article in Discover magazine (“Are We in Anthropodenial?”): “To endow animals with human emotions has long been a scientific taboo. But if we do not, we risk missing something fundamental about both animals and us.”
Even Charles Darwin, the standard of objectivity and clarity for most of the biologists I know, wrote of emotions like love and joy in the animals he observed. Later interpretations of his writings, though, often alleged, without any direct, corroborating evidence, that he was he was using these terms metaphorically.
Anthropomorphism is a powerful tool, and it must be applied carefully. Otherwise we could easily end up with cartoon-like images of the animals we were studying. This would not only obscure reality, but it would also would demean and degrade the non-human species around us.
I talked about emotions like love and happiness in last week’s blog. They were the physiological and evolutionary impetus for the formation of groups, and they were the products of hormones and brain neurotransmitters creating an existence matrix within which an organism feels content and safe (i.e. “happy”) or anxious and stressed (i.e. “unhappy”) due to the physical, visual, auditory or olfactory contacts (or lack thereof) with other members of that organism’s species. These contacts flood the herding animal or potential herding animal’s brain with soothing neuropeptides and generates a tangible force for the “pursuit of happiness” that is full of ecological and evolutionary implications!
Some researchers are extending these models of happiness into groups of insects. Bumblebees, for example, display a number of behaviors that can be interpreted as happiness or optimism especially in response to sugar-rich treats and rewards!
Experiments by Clint Perry and colleagues at the Bee Sensory and Behavioral Lab at Queen Mary University in London were published a few years ago in Science (September 30, 2016). Perry and his co-workers trained bumblebees to fly through a blue colored portal (rather than an adjacent green portal) in order to receive a sugary treat. After the bumblebee had gotten its sugary reward the experimenters then put the bees into an experimental chamber that had portals painted with an ambiguous color (purple). They found that the bees that had received the sugary treat were more likely to fly through the new colored portals than those that had not received any sugar. The researchers interpreted these data as evidence that the sugar-rewarded bumblebees had an elevated sense of optimism about the possible consequences of flying through the new type of portal.
In a second experiment, the Queen College researchers simulated a spider attack on a bumblebee (an event that does occur on flowers visited by the bees). The simulation involved a clasping device that temporarily held onto the bee by its leg. They found that bumblebees that had had a sugary treat prior to the “attack” recovered from the trauma of the attack much more rapidly than those bumblebees that had not had any sugar. The researchers interpreted these data as also indicating an increasingly positive, optimistic mind set in the sugar treated bumblebees.
Dopamine is a brain neurotransmitter typically associated with pleasure and reward. Dopamine is found not only in the synapses in mammalian brains but also in the synapses in insect brains and ganglia. When the above experiments with bumblebees were repeated using bees that had been given a dopamine blocking drug none of the positive (“optimistic”) effects of the sugar rewards were observed. These results supported the hypothesis that the sugar reward stimulated dopamine production which then caused the bumblebees to be in a more positive, optimistic state which then led them to more freely explore their environment and recover from the trauma of a simulated predator attack. These bumblebees, then, were happy!
Researchers at Queen Mary University are also looking at bees in other ways. Recently, they explored the remarkable plasticity of a honeybee’s DNA and published their results in Genome Research (August 22, 2018). All of the individual honeybees in a hive have identical DNA, but many of the individual bees have very different appearances and functions within the hive. The differences between the different castes and functional types of bee begin almost immediately as an egg hatches into a larva. Nurse bees (one of the specialized types of worker bees) feed the newly hatched larvae specific foods that alter the histone proteins in the larvae’s DNA. These histone epigenetic changes, then, regulate the subsequent expression of the larvae’s genes and control their development into a specific caste or functional class of worker.
A few years ago a paper published in Nature Neuroscience (September 16, 2012) demonstrated that some of these epigenetic changes that regulate the formation of the functional types of workers are reversible. Nurse bees in a hive could change into foraging bees in matter of a few hours depending on the specific group needs of the hive community. Further, foraging bees could likewise be changed into nurse bees if the hive’s functional economy demanded it. All of these changes were mediated through the methylation and demethylation of the histone proteins around the bee’s DNA and the altered specific activity of the genes that coded for these functional roles.
So dopamine makes bumblebees happy and optimistic enough to go exploring for food and rewards. Nurse honeybees mix concoctions that alter the shape and expression of the individual larvae’s DNA and cause those individuals to develop into different castes and functional workers. And, if the needs of a hive begin to change and greater demands for pollen and nectar gathering or rearing of the young arise, these same concoctions can alter the activity of grown bee’s DNA and cause them to take on different roles in the hive.
Bees are amazingly elegant animals!