Inés: Some time ago I made a Halloween special about cyborg beetles, which explained how
scientists had applied their knowledge of how the nervous system and the flight muscles
of insects were connected to be able to make them fly using remote controlled electrodes.
It was definitely Halloween-worthy research, and there were some very insightful commenters
who wanted to know more about the ethics of performing such an experiment on insects and
whether insects were capable of feeling pain.
So with these questions in mind, today I’m joined by the wonderful Alie from Neurotransmissions
[Alie: hi!] and we are going to be exploring all things relating to insect pain and neuroscience!
[intro animation by Caro Waro and Cristina de Manuel]
Inés: The short answer to this question is that currently scientists do not have to clear
any ethics forms in order to experiment with insects and based on current research, it
is likely that they do not experience pain in response to harmful stimuli.
Nonetheless, I’m sure you appreciate that this is a very tricky ethical topic and that
there is a lot more to it to arrive at this conclusion.
So first of all… what is pain?
Alie: Well, in basic terms, pain is defined as physical discomfort caused by illness or
injury.
From a neuroscience perspective, pain is a sensation generated by our brain, usually
when it receives stimuli that it interprets to be a sign that something is potentially
causing harm or danger.
The type of nerve that transmits these signals are known as nociceptors, which comes from
the latin nocere, “to harm”, meaning they are indicators of harm.
Inés: Think back to any time you lent on a radiator that was too hot, got your finger
jammed in something or accidentally brushed a nettle - the painful feeling you felt was
originally transmitted by a nociceptor.
However, our experience of pain is a bit more complicated than that.
Alie: Pain per se isn’t just the signal transmitted from the site of the injury by
nociceptors.
It’s a combination of the injury signal and the brain’s reaction to that injury.
So when you feel pain, it’s both the physical response to the injury, and also the emotional
response generated by your brain.
We don’t understand everything about the process of pain in humans, precisely because
it is an individual and internal response.
Some of you might be familiar with trying to explain to a doctor that you experience
pain, and being disbelieved due to a lack of obvious external symptoms, which doesn't
negate the fact that the brain is generating the sensation, and so you're feeling it.
This makes understanding pain, suffering and distress in other animals even harder, but
it's an important question in bioethics and in the field of animal welfare, because we
don’t want to cause other animals distress.
Inés: Indeed!
And it's currently impossible for us to know exactly what another animal’s experience
is in response to a stimuli, and whether the way they process the world is in any way similar
to ours or not.
However, the best we can do to tell if an animal is in pain is to look out for external
signs that could indicate distress and pain in the animal.
Alie: For instance, from the examples Inés listed earlier, you might shout out loud when
you burn yourself, or nurse a nettle rash and avoid using the affected hand to prevent
further pain.
These are signs that we can recognise as pain in humans, and we can observe similar reactions
in most vertebrates.
Inés: The most common sign of pain in animals is lameness, which is generally an abnormal
gait that minimises contact and pressure between certain body parts and the ground.
Other signs could be licking, scratching or rubbing an injured site or vocalising when
approached or when the painful area is touched, as well as other changes in normal behaviour.
Alie: While we observe these behaviours in response to painful stimuli in vertebrates,
most invertebrates don’t show the same behaviour.
When an ant loses a leg, or when a beetle is turned into a cyborg, they don’t display
characteristic signs of lameness, nor do they alter their behaviour after the injury or
experiment.
It's worth clarifying that not displaying certain external behaviours doesn’t necessarily
mean that an organism isn’t experiencing pain.
Some animals might learn to hide their pain well to avoid being seen as vulnerable and
getting targeted by predators, and I’m sure we’ve all successfully hidden a headache
from our peers.
But even bearing that in mind, it's unlikely that insects perceive harmful stimuli in the
same painful way as we do, due to their external behaviours and their substantially smaller
nervous system.
It’s difficult to say how “aware” insects are - of themselves and the world around them.
One could argue that their nervous system just isn’t complex enough to both signal
an injury and generate an emotional response to it.
Inés: Nonetheless, research into pain and nociceptors is ongoing.
Whilst most invertebrates don’t require ethical clearance to be used in laboratory
experiments, cephalopods do as they are known to be intelligent animals and they do experience
pain.
There have also been plenty of studies suggesting that basic nociceptor responses may exist
in some insects.
For instance, Drosophila larvae thrash violently in response to being poked with a hot and
piercing stimuli of a needle.
However, this may simply be an innate response against a potential sting from parasitoid
wasps that are attempting to lay their eggs inside them, and exhibiting such an avoidant
behaviour will increase the larva's survival by reducing their risk of being parasitised.
Therefore, one could expect such a behaviour to evolve and become fixed.
However, this does not necessarily mean that the larvae is distressed or experiencing pain
in the same manner as we may do, but is rather performing a reflex.
Alie: Likewise, there’s been inconclusive research indicating that lobsters and other
crustaceans, which are phylogenetically close to insects, may experience pain.
They have opioid peptides, which mediate pain responses in vertebrates, and display certain
aversive responses such as flicking their telson when being boiled alive.
The truth is we do not know conclusively whether they do experience pain or not, but in Switzerland
they elected to legislate for lobsters to be stunned or knocked out prior to boiling
them.
Inés: And regardless of whether an organism experiences pain in the same manner as we
do or not, I will always advocate for treating living organisms around us with respect.
We believe that torturing or mutilating animals for entertainment or because we expect them
to be suffering is still sadistic behaviour due to the intent behind our actions, regardless
of whether the organism affected is experiencing pain or not.
In any case, I do hope we've been able to provide further insight into the complexity
behind this question - insects probably don’t experience pain, but due to the very nature
of pain itself, we might never know for sure!
I’m also curious to know - what do you think about this topic?
Also, given you’ve made it this far I take it you’re interested in this type of question
which means that you should go check out the video we made over on Neurotransmissions'
channel, which is all about whether insects have brains or not - I mean, what even is
and isn’t a brain?!
So for more cerebral content, go head over there and please let us know what your brain
thinks about it.
And as always, thank you so much for watching us and I’ll see you in
the next one - bye!
Alie: bye!
Inés: claps
[Channel art & Animation: Caro Waro & Cristina de Manuel]
[Music by Thastor & CryoSleepKitten] [Scripting and Hosting by Alie Caldwell (Neurotransmissions)
and Inés Dawson] [Subtitled by {your name} into {language}]