2021-07-22

Can crabs and fish feel pain? Should we give them more humane treatment?

By yqqlm yqqlm

Can crabs and fish feel pain? Should we give them more humane treatment?

In the lottery of life, non-mammalian marine life Usually treated unfairly. For whatever reason, our sympathy for dogs and cats (in fact, most mammals) does not seem to extend across the surface of the ocean, but this situation, at least from a legal perspective, will change ?

Currently, the British Parliament is discussing a bill that aims to establish an “animal perception” committee that will increase the welfare protection of fish and invertebrates. Conservative Party member Barones Fox said in the debate on the bill that I was shocked by the storage and killing methods of lobsters, crabs, squids and other animals. There is now ample evidence that invertebrates should be included in the protection bill.

In Australia, the animal welfare law is “appropriate to locality”. Animal welfare laws in different states are different. Whether a certain organism is subject to animal welfare laws usually depends on whether it is classified as an animal. In South Australia and Western Australia, fish and crustaceans are excluded from animal welfare laws, and Queensland and Tasmania also exclude crustaceans from the definition of animals. Some states and regions allow commercial fishing and recreational fishing.

Then Baronnis and her colleagues make sense? Should we follow Australia? The following is about fish, crustaceans, cephalopods and their scientific explanations for pain and other sensations.

First of all, we need to emphasize that the debate on whether fish and other aquatic organisms should be subject to animal welfare laws is still not over. The debate arose mainly on whether the fish’s painful response to something like a hook in the mouth was a pain response, or an unconscious response that could be compared to a conditioned reflex. The difference between these two reactions can be clarified by the example of burning hands on the stove. When people put their hands near the stove, the first reaction is to withdraw their hands. This kind of conditioned reflex occurs between the burned limbs and the spine. The process of signal transmission occurs before people experience pain; when people take their hands away, the pain will occur alone after the human brain neocortex is processed by complex signal pathways. Without this process, we would not feel pain , Although our hands have been withdrawn from the threat.

According to Brian Kaye, a professor of medicine at the University of Queensland, fishes are different from humans. They have no neocortex and no other organs or tissues to process complex signals about pain. He said:” We have done experiments before. After removing part of the fish brain, they still respond to stimuli with the same’conditioned reflex’, just like people withdraw their hands from a hot stove. This is the so-called autonomous response. ”

He also pointed out that it is difficult for people to believe that fish do not feel pain, because we often associate these reactions with our own experiences. Everyone has their own set of core values, but The most important thing is to poke it and it will respond, so it must have feelings, but whether it has pain or not has nothing to do with the intelligence level of fish, it has to do with whether they have enough “sensing hardware”, I think fish do not !

But fish respond to painkillers

On the other hand, some people believe that pain is a necessary condition for survival, and in a broad sense, survival is proof of suffering. This view holds that a negative or painful experience needs to permanently change the animal’s future behavior towards the source of the threat. Without this experience of changing behavior, animals will continue to put themselves in danger and inevitably suffer life-threatening injuries. A large number of studies have shown that fish will quickly change their behavior after experiencing what we think is the most painful experience. It is said that anglers need to change their previous “cruel” fishing methods, and they use more in many fishing waters. Thin fishing line and better camouflage hook.

There is also physiological evidence to support this view. Pain receptors are sensory neuronal tissues in human skin, which help transmit long-distance electrical signals to the brain. According to Kurum Brown, a fish behavior ecologist at Macquarie University, their initial discovery in rainbow trout is part of the evidence that effectively “overturns” the argument that fish feel pain. Since 2002, we have known that there are nociceptors in fish. In contrast, human nociceptors are related to nerves that detect painful stimuli.

Giving fish analgesics that are effective for humans can also change their response to “pain” and fear. Professor Brown said: “All animals including fish have a sense of anxiety. In terms of observation, we use various drugs to prevent anxiety on fish, and the results show that all these drugs are effective on fish.”

What about crabs, octopuses and other invertebrates?

Although the research on the pain experience of invertebrates is not as comprehensive as that of fish, some evidence shows that the sensation of invertebrates such as crabs is not just an unconscious conditioned response to stimuli similar to reflexes. However, this The controversy is not over yet.

Professor Brown said that invertebrates and vertebrates have very different nervous systems. However, we have found pain sensation in cephalopods (such as cuttlefish, nautilus, octopus, squid, etc.) Receptors. Marine creatures like squid and octopus, their nervous system is completely independent of vertebrate evolution, they are very similar to snails.

But surprisingly, some of our painkillers are still effective for cephalopods. A study in 2018 found that octopuses became more social and like to interact with other companions after taking drugs. This contact and interaction reflects a significant difference in drug use.

Although researchers have not found pain receptors on the bodies of crustaceans such as crabs, prawns, and crayfish, there are other clues that negative experiences can lead to long-term behavioral changes. In the experimental scenario, the crustaceans would avoid the objects being shocked, and the crayfish that received the shock had higher brain serotonin and blood sugar concentrations. The researchers attributed this to the stress response.

A 2014 study also found that an anti-anxiety drug can reduce the “fear” of lobsters. Professor Brown said: “When we talk about pain, we are actually talking about the ability to feel. It seems to be a sudden attribute from a complex nervous system. If you have a lot of sensory input from touch, smell, etc., and they are all in a state of centralized processing, then pain is a conditional feedback mechanism.”

But Professor Kaye said that similar experiments have been carried out in invertebrates such as fish. Part of the brain and nervous system of these animals has been removed, but their “autonomous response” to stimuli has not changed. We conducted experiments on mollusks, and the results were the same. Octopuses are a member of the mollusk family. They do not have “hardware organization” such as pain receptors, but people still say that they are intelligent creatures. In fact, the body structure of these animals Very complicated, but far less complicated than humans.

So, what are our views on whether animal cruelty laws should be used for humans to deal with fish and crustaceans? The scientific research conducted by Professor Brown and Professor Kaye may help ethicists solve these problems, but they say they are not ethicists.

Professor Brown said that with the continuous advancement of science and technology, the law on the humanitarian treatment of animals is likely to be extended. The real question at present is how far is the evolutionary history of animal pain receptors? What animals may be conscious, and what is their minimum tolerance range? I think crustaceans, ants, wasps and bees have pain perception.

But Professor Kaye said: “There is sufficient scientific evidence to prove whether pain is a common feature. We need to discern whether animal rights need to be included in the law, but this is not always reasonable. Yes, eventually any animal will have a sensory nervous system.”