Do oysters feel pain?

Do oysters feel pain when you bite into the inside, or when you crack open the shell? I tried google searching it to no avail. When you bite inside the oyster or when you break the shell to open the oyster, does it feel pain?

EDIT: (Since some people think that mine is a duplicate) I'm asking if the oysters feel pain when we eat the inside, or when we crack open their shell. To the least of my knowledge, ants and oysters have a different body so I don't know if they do feel pain.

There are fundamental problems with defining what it means for an animal to feel pain, especially when the animal is a life form as different from us as an oyster.

I wasn't able to find any specific info online about oysters, but there is quite a bit of information that allows us to reason by analogy with related species.

Oysters are molluscs, and molluscs do have brains and sensory systems, but their level of sophistication varies a lot. Cephalopod molluscs, such as squid, octopuses, and cuttlefish, have extremely sophisticated nervous systems, and it has been argued (Peter Godfrey-Smith, Other minds, 2016), that we should think of intelligence as having arisen twice on earth through parallel evolution: once in vertebrates and once in the cephalopods. Cephalopods have sophisticated communication systems, and they can use tools and solve problems. There has been extensive research on pain in cephalopods.

So it's inherently pretty plausible that cephalopods can (in some difficult to define sense) suffer and feel pain, and by extension that their less advanced cousins the oysters can as well. However, the nervous system of an oyster is much more rudimentary than that of a cephalopod. A better analogy might be with snails, and there is some research on snails. They avoid damaging stimuli, have opioid systems, and respond to morphine and naloxone analogously to humans (e.g., showing less aversion to a hot plate when they've been dosed with morphine). So it seems likely to me that oysters can feel pain (for some reasonable definition of the word), but this whole area is one where people don't really know the answers to the questions or how to construct the philosophical foundations.

It is very unlikely that oysters feel pain however it's not clear what the question actually means

What does it mean to say something feels pain? The most reductive biological interpretation is to say that "feeling pain" is simply the capacity to sense damage, or the threat of damage, to the body and communicate that to the nervous system in a way that elicits a response. However, that's not really what we're usually talking about feeling pain, but rather the unpleasant sensation that accompanies these signals.

And that's more difficult, because we know that the two are not equivalent. For example, disabled athletes are able to improve performance by inflicting injuries they cannot directly feel, but their bodies still respond to. In this case the reductive biological pathways are active but the sensation of pain is absent.

Oysters have no brain, but simply an couple of enlarged ganglia that perform some rudimentary centralised functions, and so it seems very unlikely indeed that they are capable of experiencing any sensations and thus almost certainly do not experience pain in the sense we would usually use of "feeling pain". But they do have a nervous system which can respond to stimuli including damage, or threat of damage, to their tissues so they have what could be described as having a pain response.

Referring to this research article on PubMed, oysters have their sensory system and organisation like humans. So any change or invasion in the system of Oyster is communicated through sensory organs. So Oysters do feel pain. It's like, pain is a result of something harmful or negative is going on.

Regarding break opening the shell, as it is a sort of insult to their protective system, they have the sense of removal of the covering, we can term it as 'pain'.


Invertebrates are the most common animals on earth, composing 97% of known species (“Articles 16 September 1988,” n.d.), and have complex behavior and nervous systems. While it may be impossible to tell conclusively whether a non-human species can feel pain or not, there are concrete factors that may increase the chance that a given species feels something analogous to pain in humans. There are six such factors that are experimentally verifiable, and can be studied in species both related and distant from humans: identified pain-related neurons and brain structures, the presence of natural opioids, behavioral responses to damaging stimuli (either general responses or altered response to the damaged body part), evolutionary similarity to humans, and a wide repertoire of behaviors.

Raw oysters are alive when you eat them – but do they feel pain?

If you’ve ever eaten raw oysters lying open on a bed of ice with a fresh wedge of lemon, or Tabasco or vinegar to drizzle over them, those oysters will have been alive.

Those salty little (supposed) aphrodisiacs were living and breathing organisms when you snapped them for Instagram and tipped their shells towards your lips… and that’s a good thing.

Dead oysters cannot be eaten raw, because they contain bacteria that can be very dangerous for humans. If you eat a dead oyster raw, you’re probably going to get poorly (fever/chills, vomiting, diarrhoea – among other symptoms).

But if you want to enjoy your oysters raw (and alive), are you causing them pain?

Seafish, a non-departmental public body set up to improve efficiency and raise standards across the seafood industry, say that whether or not oysters feel pain is still up for debate.

‘Unfortunately there’s no definitive proof either way. There are groups that argue oysters might feel pain, and others who say because they don’t have a central nervous system then they don’t feel pain in the way other seafood species might. We currently don’t have research in this area.

‘As for when they actually die, this is likely to happen when they are shucked, rather than when they are chewed or swallowed.’

Shucking is when the two shells of an oyster are levered apart and fully opened.

So oysters probably aren’t alive when you bite into them or when they hit your stomach if you choose to swallow them whole.

If you’ve bought oysters to open and eat raw at home, you can tell whether an oyster is safe to eat raw quite easily.

Is the shell completely closed? If so, the oyster inside should be alive.

If the shell is slightly open, flick it with your finger. The shell should close.

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If it doesn’t, that means the oyster inside is dead and should only be eaten cooked.

Bruce Rennie of chef and owner of The Shore, Penzance told ‘You really want to eat the oysters when the lid is tightly closed and shuck them yourself to guarantee freshness.

‘Also it’s best to store them in the fridge with the deep part of the shell downwards to retain the moisture before preparing them, they should easily live 5-7 days in a properly chilled fridge like this.

‘The reason for eating them alive is simply for freshness and flavour as they still have most of their iron/sea flavoured juices within the meat.

‘Personally, I love the iron flavour. They are far more versatile than most people give credit for. Currently I have Porthilly oysters on poached with mackerel, cucumber, sesame and wasabi…but they are also great breaded and fried or tempura as an easy introduction to them.

‘They were classically paired with meat dishes due to the strong iron flavour and used to be cheaper than most meat.’

Remember that if you buy shell-less oysters in a bag or jar, they’re absolutely not intended to be eaten raw. You must cook them.

What About Shellfish?

When people decide to stop eating animals, they may leave some species on their plates because they believe that those animals don’t feel pain. It’s now generally accepted in the scientific community that mammals, birds, and fish have feelings, preferences, and the ability to sense pain. But what about shellfish?

The term “shellfish” covers a wide range of invertebrate aquatic animals used by humans as food. The most frequently eaten shellfish are crustaceans (shrimps, lobsters, and crabs) and mollusks, a broad category that includes cephalopods (squids and octopuses) and bivalves (animals with hinged shells such as clams, oysters, and scallops).

Cephalopods are considered among the most intelligent of the invertebrates. An octopus named Otto in a German aquarium passed the time by juggling the hermit crabs in his tank.

He mystified the staff by causing frequent electrical outages until they finally caught him in the act of climbing up on the edge of his tank and firing a jet of water at the light fixture. Octopuses have even successfully navigated mazes. Squids and octopuses have very different physiology than mammals do, but they can play, learn, and think—and they don’t deserve to be served for dinner.

Some people believe that shrimps, crabs, and lobsters—all of whom are more closely related to insects than to vertebrate animals—cannot feel pain at all. But recent scientific studies have shown that crustaceans have central nervous systems very much capable of generating the sensation of pain. Crustaceans release stress hormones (analogous to our adrenal hormones) in response to painful events. If you’ve ever seen a lobster or crab lowered into a pot of boiling water, you’ve seen these animals fight just as hard for their lives as any other animal would in the same situation. A lobster can’t scream, but that doesn’t mean he doesn’t feel agony in the time it takes for him to boil to death. And crustaceans suffer in other ways—they are often transported alive to restaurants and grocery stores and crowded into tanks where they are so stressed that their claws must be banded shut to prevent them from attacking each other.

Without obvious legs or faces, bivalves look less animal-like than other shellfish. But they’re capable of a surprising variety of behavior. Scallops can swim away from predators by “flapping” their shells. They can detect light and movement with small eyes that are located around the perimeter of their bodies. Clams can escape by burrowing through sand. Mussels are able to gradually move to a better home, reanchoring themselves in a new location. Oysters protect their soft bodies by snapping their shells tightly closed at the first hint of danger.

As we learn more about the many animal species with whom we share this planet, we keep discovering that they are more intelligent, more feeling, and more empathetic than we had previously realized. The evidence for sentience in squids, octopuses, and crustaceans is increasingly clear. We don’t yet know whether oysters feel pain, but if they do, they represent a very large number of suffering animals—a single meal might require the deaths of 12 or more oysters. We don’t need to consume oysters, scallops, and clams to survive. Is the flavor of Oysters Rockefeller or New England Clam Chowder so important to us that we can’t give these animals the benefit of the doubt?

Little-known fact about raw oysters is disturbing people for a good reason

They&aposre a popular delicacy across the world and considered an aphrodisiac by many.

But while lots of people enjoy eating oysters, it seems there&aposs one thing people don&apost really know about them.

And that&aposs that raw oysters, the kind served on ice with a wedge of lemon, are still alive.

It&aposs no secret, but it&aposs something that people are still disturbed to learn.

Learning the truth has led to lots of questions on social media, including if oysters feel pain when we eat them.

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One person wrote on Twitter: "Just read that raw oysters are still alive when you eat. Thank god I don&apost eat shellfish."

Another added: "I just found out that oysters are alive when you eat them and I feel really guilty I’m gonna cry."

Despite the fact that it sounds incredibly gross and cruel, it&aposs actually better for you to eat them in this way.

That&aposs because dead oysters which are eaten raw can contain bacteria that is harmful to humans and can make us ill - with symptoms including a fever, vomiting and diarrhoea.

Do oysters feel pain when you eat them?

Seafish , an organisation set up to raise standards in the seafood industry, say that the debate of whether or not oysters feel pain is still ongoing.

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A spokesman told Metro: "Unfortunately there&aposs no definitive proof either way.

"There are groups that argue oysters might feel pain, and others who say because they don&apost have a central nervous system then they don&apost feel pain in the way other seafood species might. We currently don&apost have research in this area."

When do they die?

As for when exactly they die, this is also up for debate - is it when they are shucked? Or when you eat them?

Seafish have a theory about this as well.

"This is likely to happen when they are shucked, rather than when they are chewed or swallowed."

They think this because an oyster&aposs heart is right next to the bottom adductor muscle, so separating it from the shell kills it.

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Things we&aposve all been doing wrong

How can I tell if an oyster is dead?

If an oyster is dead it should be eaten cooked, not raw, or it could make you very ill.

Recently a 71-year-old man died from contracting a flesh-eating bacteria from a dead oyster.

So how do you avoid making this mistake?

There&aposs an easy way to check whether the oyster is alive - and it&aposs all to do with the shell.

If the shell is tightly closed then the oyster inside should be alive.

If the shell is ajar slightly, give it a light flick. If it closes, the oyster is alive.

If the shell doesn&apost close, then most likely it is dead and needs to be cooked.

Oysters aren&apost the only food that people eat while it&aposs still alive.

Other foods include shrimp, sea urchins and octopus - though these can also be eaten cooked as well.

Why we eat oysters alive

Most people think it's a food safety issue. Keep the oyster alive as long as possible, to reduce the risk of bacterial contamination. And there is a little bit of truth to that. Oysters can carry a scary flesh-eating bacteria called vibrio vulnificus. You can get it from oysters or from swimming in warm brackish water. But let's put that into perspective.

Julie Qiu: "The risk of running into a bad oyster is lower than people think it is. My biggest pet peeve is that people go crazy over one bad oyster but they don't really care that hundreds of thousands of pounds of lettuce are contaminated with salmonella"

About 100 people die from vibrio infections (including from vibrio vulnificus) each year, about 450 die from salmonella. Plus, the FDA requires that oyster farms have to test water quality before sending oysters out to markets and restaurants. And that's important, because oysters are filter feeders. They soak up basically anything that's in the water around them — including fecal matter which can come from rain runoff.

But there's a clever way to check if your oysters are good.

Julie Qiu: "one thing that you can ask for is a shellfish tag, which every retailer or restaurant is required to have for every bag of oysters that they purchase for up to 90 days after they make that purchase. So that tag, if they don't have it, don't eat those oysters."

This tag is a way for restaurants to track where and when their oysters were farmed. Qiu says that she looks for the most recent dates on the tag. Anything further out than two weeks won't taste as good and increases the risk of a bad oyster.

Some chefs may look at you funny for asking for the documentation, but it's a strategy that apparently works.

Julie Qiu: "I've had thousands of oysters and never had a bad one"

Ok great, so basically, oysters are safe, why on earth are they sometimes alive when we eat them??

Julie Qiu: "You really want your raw shellfish to be really fresh and the freshest you can get is something that is recently killed, so it goes back to not only the food safety but the actual taste and texture is going to be far superior when it's a fresh oyster."

So yeah, freshly killed oysters taste better. And it's hard to tell exactly when an oyster dies, because before it's served, it's shucked. It's not a gentle process. Shucking involves separating the oyster's abductor muscle from the shell. This muscle gives the oyster control over opening and closing its shell. Similar to how your spinal cord helps you move. So, severing the their abductor muscle is almost like severing your spine. Yikes.

Most restaurants in the US keep their oysters alive — on ice — up until this shucking process, which afterwards, either leaves the oyster dead, or immobile. Since they don't move around much in the first place, it's not easy to tell which.

So you're eating an oyster that was either just killed or is dying. And that seems pretty cruel, right? But considering that the oyster's biology is very primitive, it's possible they might not even feel pain at all.

Julie Qiu: "They don't have a brain, they're not really processing pain the same way the same way we are feeling so I don't think they're feeling pain the same way we are thinking of it."

So really, it's up to you. If you don't want to eat oysters, that's fine. If you do, you'll be far from the first.

Julie Qiu: "It's one of the few foods that have not changed for thousands and thousands of years so being able to appreciate that is something that's really special and remarkable and something that should be celebrated for what it is."

For more information about oysters from Qiu, check out her blog In A Half Shell or follow her on Instagram.

EDITOR'S NOTE: This video was originally published in September 2018.

The Benefits of Oyster Farming

All of man’s activities are a give-and-take between pros and cons. Even harvesting grains or fruits requires fossil fuels to power tractors, which causes pollution. But time and again, the pearling industry has demonstrated that it is committed to the wellbeing of marine ecosystems. In fact, farming oysters actually helps the environment.

Consider that some oysters filter between 70 and 100 liters of water every hour, sifting particulates and materials from the oceans. Even after factoring in the carbon footprint of man in this industry, the net environmental outcome is positive: water quality is enhanced over-exploitation is kept in check through intelligent farming forests are encouraged to thrive (deforestation causes runoff, the chemicals in which threaten oysters) pesticides are unneeded no grain or nutrient supplements are required to feed oysters and where pearl farms move in, biodiversity increases.

Do bivalves feel pain?

Do simple molluscs (clams, oysters, muscles) feel pain? They have simple ganglia, but no brain. They are not motile, so they (seemingly) have no need to feel pain from an evolutionary stand point.

While your question is very valid, the premise that bivalves are strictly sessile isn't. See this example.

I recall that scallops and a few others are the exception, but that most don't move, I could he wrong.

I'm sure this is a widely debated topic, but here is a good start debating that invertebrates are incapable of pain.

That page talks about insects, but from what I understand the decapoda are believed to experience pain. That is your crabs, your lobsters and your shrimp.

It would be a fairly horrible quirk of evolution to enable a creature that is completely immobile, to feel pain.

Not all bivalves are sessile. Most are motile when young but become sessile such as oysters. Some bivalves such as scallops are capable of swimming quite energetically into maturity. As for the original question I would say very likely not, they can respond to stimulus but their response probably would not be characterized as "feeling pain". They lack the capacity to register the sensation in a way beyond reflex.

Exactly, my thoughts exactly, especially given how simple their nervous system

Too true. Perhaps that's why the only animals that don't move don't feel pain ( adult tunicates & sponges. cnidarians on the edge). However if you want to claim bivalves don't move you're dead wrong.

To my mind, the key question here isn't so much "pain" but "experience". We don't really know what subjective experience is or what causes it, so it's hard to guess how widely distributed it is in the animal kingdom. People have estimated everything from "just humans" to "all animals." It's not really tractable to experimental research, either.

For what it's worth, my own guess would be that they probably don't experience much. Although they do exhibit increased heart rate when they smell crabs and other predators.

That's a really good point, we can't know if anyone but ourselves truly feel pain, but we can observe certain reactions to typically painful stimuli. But just because something reacts (heartbeat increase, retracting appendages, releasing hormones) does not equate fear or pain. Plants release hormones when there is noxious stimuli but don't feel pain or fear

There ways to try and test it, and it is done, I think the journal Applied Animal Welfare Science has some articles. They mostly involve either the presence of altered behaviour which endures after the stimulus, like limping or rubbing the affected area, and whether or not afflicted animals will seek out painkillers when provided (sometimes in spite of unpleasant taste, and its usually demonstrated that healthy animals don't seek them out first). The articles I have read are mostly insects and fish since the notion of other vertebrates having an experience of pain is pretty well accepted. Now there are counter arguments regarding fish that their brain structure and such are too different to allow them to feel pain the same way as us, but I think that the demonstrated responses speak for themselves, and it's more likely that their nervous system produces the response in a slightly different way. Pain is useful after all. Those methods of research aren't really suited to non-motile creatures though.

The esteemed Dr F. Mike has this to say on the matter.

Salient points from this excellent assay:

Clams [. ] don't have central nervousness, no spinal cord.

I think you got downvoted as you made an argument with a few illogical statements, not because it was some Reddit conspiracy. Things like:

"You see feeling pain is the way that a body gets the organism to avoid detrimental (bad) behaviors. You can understand that as long as something has the ability to move and avoid this, they're going to have a pain circuit."

I think this is you anthropomorphising animals, looking at their behaviours through a human lens. Amoeba and phytoplankton will also move from danger, but I doubt anyone would claim that this indicates a pain response.

Grouping animals by edibility is also hardly a valid scientific grouping. The DNA % argument you make is also pretty irrelevant: we share 50% of our sequence with bananas, but this doesn't mean that bananas can feel pain either.

Others here have made the more accepted evolutionary argument regarding (some, adult) bivalves: if they cannot move, why bother investing energy on a neurological process by which they could perceive pain, given that they are unable to do anything about it when it happens?

Why Everyone Should Eat Oysters

It makes sense to prevent the suffering of other living organisms whenever possible, which carries over to our food choices. Most vegans, vegetarians, and plant-based eaters draw the line at plants versus animals. In other words, from an ethical standpoint, plants are okay to eat, but animals are not.

The reason? As far as we know, other animals can suffer just like humans because they too have nervous systems, whereas plants do not have nervous systems and therefore presumably lack the ability to suffer. Oysters also lack nervous systems, making it unlikely that they feel pain [1].

One ethical argument against eating oysters is that they take action when they sense danger or feel threatened, but so do plants, in a variety of ways. It’s possible that organisms without nervous systems, like oysters and plants, can indeed feel pain, but if that’s the case, then oysters do not feel any more pain than spinach, corn, or peas.

Unlike most farmed food, oysters actually have a BENEFICIAL impact on the environment.

While the sustainability of much fish is dubious, oyster farming is a regenerative farming practice, actually improving the environment, not just lessening the burden.

Unlike farmed fish, pigs, and chickens, oysters do not require agricultural feed. Oyster farmers simply run sea water through bags or tanks of oysters, and the oysters feed on phytoplankton or small bits of algae naturally present in the water. As a result, oysters are one of the most sustainable foods on the planet.

What’s better than zero carbon footprint? A negative carbon footprint. Oysters are like little carbon capture tools, purifying the water they’re in and capturing CO2 from the atmosphere. Ninety-five percent of oysters we eat are sustainably farmed in a way that benefits the environment, removing any concern of overfishing (the other five percent are typically wild caught) [3].

Our oceans are becoming over-carbonized, and oysters are a great way to remove that carbon from the ocean and turn it into pure human nutrition.

Gram for gram, oysters are literally the most micronutrient-dense food on the planet, second only to liver.

Think of oysters as organic whole food multivitamins served on a half shell. Not only are oysters nutrient-dense, they are full of some of the vitamins and minerals in which Americans are most deficient, namely Zinc, Iron, and Vitamin D.

The above chart shows the average % weekly value of the ten most important micronutrients for different foods. A 3.5-ounce (100 gram) serving of oysters also contains the following daily values:

  • Vitamin D: 80% of the Recommended Daily Intake (RDI)
  • Zinc: 605% of the RDI
  • Thiamine (vitamin B1): 7% of the RDI
  • Niacin (vitamin B3): 7% of the RDI
  • Vitamin B12: 324% of the RDI
  • Iron: 37% of the RDI
  • Magnesium: 12% of the RDI
  • Phosphorus: 14% of the RDI
  • Copper: 223% of the RDI
  • Manganese: 18% of the RDI
  • Selenium: 91% of the RDI

Just a few oysters, about 68 calories wroth, gives you a week’s worth of immune-boosting Zinc and one to three days’ worth of Vitamin D, Selenium, Copper, and Vitamin B12 [6].

Oysters are high in omega-3s and low in mercury, a common concern in seafood.

Oysters fall within the top-ten most omega-3-rich sources of popular seafood, with about as much omega-3 as swordfish and bass, but with significantly less mercury.

In fact, oysters contain all three major classes of omega-3s: ALA, DHA, and EPA.

Among many other roles, EPA helps to reduce inflammation, while DHA is important for brain development in kids and brain function in adults. The form of omega-3 typically found in plants, ALA, must first be converted into EPA and DHA before it can be used by the body. Unfortunately, this conversion process is inefficient only 1–10% of ALA is converted into the bioavailable forms EPA and DHA.

Getting enough EPA and DHA is important for health and typically requires consuming seafood like salmon and sardines. As an alternative, oysters offer a way to get more bioavailable omega-3s without eating fish [7].

While mercury is a somewhat controversial topic, it’s advisable to avoid regular consumption of high-mercury seafood such as shark and swordfish. Among all seafood, only scallops, shrimp, and clams have a lower mercury content than oysters.

Oysters contain a recently discovered, natural antioxidant called DHMBA that exhibits powerful antioxidant effects.

In test tube studies, DHMBA (3,5-Dihydroxy-4-methoxybenzyl alcohol) is shown to be 15x more effective in reducing oxidative stress than Vitamin E [8]. In mice, supplementing with DHMBA-rich oysters also reduces markers of oxidative stress, including inflammation [9].

Test tube and animal studies can’t be used to predict outcomes in human studies, so more research is needed to determine whether DHMBA is effective at fighting free radicals in humans, but the early research looks promising.

Oysters come in all shapes and sizes.

Today most consumers prefer smaller, more petite oysters, which are harvested between eight months to two years in the U.S., depending on where they’re grown. But, like plants, oysters continue to grow if not cultivated, and if left to grow for four or five years, oysters can grow to over seven inches in length, as chef Dan Barber shows in the photo above, and describes below:

Oysters can be eaten fresh or smoked (canned).

Oysters aren’t only for fine dining or eating raw. Smoked and canned oysters make a great (occasional) afternoon snack, once every week or two. While oysters are extremely nutritious, eating a can every day would likely be too much of a good thing.

Once you get used to them, oysters are a delicious treat, and a good investment.

Like wine, chocolate, and coffee, oysters can be an acquired–and expensive–taste, but once that taste is acquired, they make a delicious snack or appetizer. Trying different oysters and noting the subtle differences between Kumamoto, Miyagi, and Fanny Bay, as well as experimenting with lemon juice, tabasco, vinegar, and horseradish toppings, makes for a fun culinary experience.

Oysters at a high-end restaurant can be expensive, but learn to shuck and prepare your own oysters and you can get them for much cheaper, sometimes .75 per oyster or less.

A half dozen oysters would cost less than five bucks, and provide more nutrition for that price than nearly any other food. Plus, those six oysters would have filtered and cleaned over 50,000 gallons of sea water during their 1–2 years of life [10].

For a country that’s overfed and undernourished, and a world that’s experiencing a crisis in ocean health and marine pollution, oysters are one of the best investments you can make.

The Case for Vegans Eating Oysters, Mussels, & Other Invertebrates?

If you’ve reached this article, then you are well acquaint e d with the definition of veganism, which is a stance against the purposeful exploitation of animal species as is practical. It’s troubling to find numerous members in the vegan community supporting the exploitation of animal species based on articles unsupported by a single shred of evidence. More alarming is how these articles try to establish oysters, mussels, and even other animals in the vegan community as being akin to plants, rocks, and as one stated, “a disembodied finger.”

Modern molecular and taxonomic advances have led scientists to base classification of living beings in very specific ways. I won’t further delve into the subject, but I will say that oysters and other animal species are not comparable to plants. The plant and animal kingdom are separate for good reason regardless of what supporters of bivalve eating in the vegan community will have you believe. One of the most important differences is that plants do not have a nervous system while bivalves do.

The same bivalve eating individuals claim that mussels and oysters are not sentient because they do not have “brains,” and while it is true that mussels and oyster do not have a brain in the sense that you or I do, they do have ganglia. Ganglia, in simple terms, is basically their form of a brain — how they get their systems to function and respond when they need to. Yes, invertebrates have much simpler nervous systems than vertebrates, but they still have nervous systems. How developed their nervous system depends on the species. More importantly, their form of a nervous system allows them to respond to their living conditions and survive in them.

Most, if not all, invertebrates have the capacity to detect and respond to noxious or aversive stimuli. That is, like vertebrates, they are capable of ‘nociception” (Smith 1991). Responses to negative stimuli, such as pain, which is very subjective depending on the individual, can indicate that something more than a simple nociceptive reflex is involved. Together, they may help the animal to recover from damage caused by the painful event and avoid being harmed in the future” (Smith 1991). While invertebrates probably do not feel pain in the same way humans do, Smith stated that, the issue isn’t closed. He further stated that, “Mather (1989) suggests, we should simply accept that these animals ‘are different from us, and wait for more data.’

It would be unreasonable to apply the same guidelines of pain that we apply to ourselves and other vertebrates to species that are completely different to us. Smith (1991) warned that, “pain might incorrectly be denied in certain invertebrates simply because they are so different from us and because we cannot imagine pain experienced in anything other than the vertebrate or, specifically, human sense.”

Unfortunately, “reports are notably lacking in sessile molluscs, primarily due to the difficulty of quantification of behaviours that occur in these generally small animals whose behaviour is characterized by minimal movement carried out over comparatively long time periods. Such movement may, however, be critical in survival and its quantification may provide insights into strategies and environmental conditions of consequence for this important animal group (Robson, Wilson, and Garcia de Leaniz 2007).”

Supporters of vegan bivalve eating claim mussels and oysters cannot respond to stimuli simply because their reaction to it doesn’t stem from a central nervous system while ignoring the fact that they do have a nervous system. However, if mussels and other bivalves are but barely living filtering rocks without the ability to respond to, well, anything, why do mussels, for example, have a need to detect and respond to predators, or even respond to stress at all?

As you may have noticed, I’ve taken most of my text from scientific literature. I am doing this on purpose to demonstrate that I am backing all my statements and thoughts on this subject with actual scientific evidence. To counter the misinformation being used to justify animal exploitation and to bring accurate science into the discussion, below, I attempt to set the science straight and provide examples that exemplify how those in support of eating these bivalves are erroneously advocating for unethical behavior in the vegan community. I also do not try to make the case (or not) for sentience because it just doesn’t make sense. You’ll see what I mean.

“Scientifically accepted definitions of pain and nociception neatly distinguish these concepts (e.g., Merskey and Bogduk 1994), but drawing a line between the two can be difficult in practice. Furthermore, no experimental observation of nonverbal animals (nonhumans) can demonstrate conclusively whether a subject experiences conscious pain (Allen 2004). Suggestive evidence for painlike experiences in some animals is available, and nociceptive responses measured at the neural and behavioral levels in molluscs have provided evidence that is both consistent and inconsistent with painlike states and functions. Unfortunately, inferences drawn from the relatively small body of relevant data in molluscs are limited and prone to anthropocentrism. Identifying signs of pain becomes increasingly difficult as the behavior and associated neural structures and physiology diverge from familiar mammalian patterns of behavior, physiology, and anatomy, making interpretation of responses in molluscs particularly difficult.” This does not only refer to cephalopods though. This is a general statement inclusive of all mollusks.

Gartner & Litvaikis (2013) found that blue mussels “selectively alter byssal thread production and movement in the presence of injured conspecifics and potential predators.” In addition, Robson, Wilson, and Garcia de Leaniz (2007) found that “mussel response to predation is graded and complex and may well indicate animal-based assessments of the trade-off between effective feeding and the likelihood of predation.” Couldn’t this be considered a form of decision-making?

Opioid receptors have also been observed and studied in mussels (Aiello 1986 Cadet and Stefano 1999) AND to quote the biggest proponent of bivalve eating in the vegan community, the Sentientist herself, “Many animals have opiate receptors, indicating they are making painkillers and regulating pain within their own nervous system.”

Well, “investigations have shown that similar opiate systems may have a functional role in invertebrate nociception (Fiorito, 1986 Kavaliers, 1988). In addition, “Opiate binding sites, with properties similar to those of mammalian opiate receptors, have been shown to be present in the neural tissue of the marine mollusk Mytilus edulis (Kavaliers et al., 1985).” It should be noted that M. edulis is a species of mussel.

In summary, studies that show the opposite of what the bivalve eating supports claim exist. Mussels have responses to stimuli (Stephano 2002), including stress (Anestis et al. 2008), and as we have seen, may make decisions based on threats of predation ((Gartner & Litvaikis (2013) Robson, Wilson, and Garcia de Leaniz (2007)).

Unlike plants, but like most other invertebrates, oysters do have nervous systems. How developed those systems are does not automatically reduce them to the level of plants. Because they have simple nervous systems does not mean that one can deduce that they are unable to respond to stimuli or have the inability to experience their own environment, particularly because we are incapable of truly understanding what pain and sentience are in other animals.

Carroll & Catapane (2007) stated that, “Bivalve molluscs [this includes oysters] have a relatively simple bilaterally symmetrical nervous system composed of paired cerebral, visceral and pedal ganglia, and several pairs of nerves. The cerebral ganglia (CG) are connected to the visceral ganglia (VG) by a paired cerebrovisceral connective and the VG innervate each gill via branchial nerves.”

Unfortunately, based on my review of the available data, there aren’t that many studies focused on oysters. And those that exist seem to have an interest in human application or farming. As of this date, I could not find a specific paper devoted to the examination of nociception in oysters per se. However, that is not conclusive proof that nociception does not exist in oysters.

“The full length cDNA of a homologue of δ-opioid receptor (DOR) for [Met(5)]-enkaphalin was cloned from oyster Crassostrea gigas” by Liu et al (2015). These results, as outlined by Liu et al. (2015), “collectively suggested that CgDOR for [Met(5)]-enkephalin could modulate the haemocyte phagocytic and antibacterial functions through the second messengers Ca(2+) and cAMP, which might be requisite for pathogen elimination and homeostasis maintenance in oyster.” Varga et al. (2004) describe, “delta opioid receptor (DOR) agonists are attractive potential analgesics, since these compounds exhibit strong antinociceptive activity…”

In addition, mu opioid receptors have been found in both blue mussels (Mantione et al. 2010) and oysters (Zhang 2012) these receptors are also antinociceptors.

Opioid peptides have also been documented in oysters. Liu, Chen, & Xu’s (2008) described that, “The nervous and immune systems of invertebrates can exchange information through neuropeptides. Furthermore, some opioid peptides can function as endogenous immune system messengers and participate in the regulation of the immune responses.” Their study concluded that their “data strongly suggests an involvement of opioid peptides in the regulation of the antioxidant defence systems of the Pacific Oyster.” Endogenous opioid peptides have been described as inducing, “analgesia in humans and antinociception in animals. These peptides act in several regions of the CNS to mediate pain control, because antinociception is observed in animals whether endogenous opioid peptides are administered into the peripheral circulation into spinal sites or into various regions of the brain, such as the raphe nuclei, PAG region, or medial preoptic area. Many events or stimuli that are experienced as painful, stressful, or traumatic can induce the release of endogenous opioid peptides. These peptides then act to make humans and animals less sensitive to noxious events by inducing euphoria and analgesia or antinociception(Froehlich 1997).”

Why would oyters have any of these receptors or mechanism for antinociceptive activity? If they have antinociceptors, does that mean that they could have noticeptors as well? Regardless, it has been established above that opioid receptors have been found in oysters, and “opiate systems may have a functional role in invertebrate nociception” (Fiorito, 1986 Kavaliers, 1988).

The following studies further show that oysters, although thought of as simplistic as plants by many, have nervous systems that are still complex and may use many of the same responses and regulations as other animal species.

Harrison et al. (2008) found that their study confirmed and quantified, “histamine as an endogenous biogenic amine in C. virginica in the nervous system and innervated organs…Histamine is a biogenic amine found in a wide variety of invertebrates, where it has been found to be involved in local immune responses as well as regulating physiological function in the gut. It also functions as a neurotransmitter, especially for sensory systems1. Histamine has been well studied in arthropods and gastropods, but has been rarely reported to be present or have a function in bivalves other than the limited reports identifying it in ganglia and nerve fibers of the Baltic clam.” The authors further stated that, “Bivalves, including the oyster, Crassostrea virginica, contain dopamine, serotonin and other biogenic amines in their nervous system and peripheral tissues. These biogenic amines serve as neurotransmitters and neurohormones and are important in the physiological functioning of the animal.” They also stated that,”The mantle rim of bivalves is a sensory structure containing various sensory receptors. The involvement of histamine in sensory systems of invertebrates, particularly gastropods, coupled with our preliminary physiology research, strongly suggest histamine to be a sensory neurotransmitter in the mantle rim of C. virginica.”

In addition, Park et al. (2007) were able to clone and characterize, “Lipopolysaccharide-induced TNF-alpha factor (LITAF) is an important transcription factor that mediates the expression of inflammatory cytokines” in the Pacific oyster Crassostrea gigas.” Interestingly, Zhang & An (2007) describe that, “there is significant evidence showing that certain cytokines/chemokines are involved in not only the initiation but also the persistence of pathologic pain by directly activating nociceptive sensory neurons.

Like in mussels, it has been shown that oysters control the beating of their cilia to draw in water, which they do as filter-feeders. Carroll & Catapane’s (2007) study demonstrated that there is a “reciprocal serotonergic-dopaminergic innervation of the lateral ciliated cells, similar to that of M. edulis, originating in the cerebral and visceral ganglia of the animal…” This, therefore, means that ganglia (their nervous system) regulates movement/behavior. Perhaps, like in mussels, oysters also have the ability to actively control, based on a form of decision-making, why they employ the types of ciliary movements they do.

Regarding predation, “Bivalves readily utilize chemical exudates that emanate from predators and from injured conspecifics to evaluate predation risk (Caro & Castilla 2004, Cheung et al. 2004, Smee & Weissburg 2006b) (Robinson et al. (2014). A study by Robinson et al. (2014) found that in the presence of predators, “oysters grew shells that required more force to crush and resultantly were afforded greater protection from crab predators.” This supports recent studies that “have shown that oysters react to gastropod and crustacean predators by producing thicker, heavier shells (Newell et al. 2007, Johnson & Smee 2012, Lord & Whitlatch 2012)”(Robinson 2014). Again, these are examples that oysters actively respond to their environment (predation in this case) as any other animal species would when threatened.

The studies that I’ve quoted above are only bits and pieces of a large body of data that is yet to be uncovered or even studied. What all this means when put together is yet unknown because few studies have been done. However, it shows that although oysters have simple, yet efficient nervous system to respond to the type of lifestyle that they live, they also have sensory structures and receptors like those found in other animal species. In essence, they are still nothing like plants regardless if they are sessile species. The fact that they are sessile still does not mean that they do not need to react to their environment if simply to protect themselves and carry out functions in order to survive.

Sea Urchins

The same supporters of mussel and oyster eating have begun to further open their menus to other animal species not categorized as bivalves because of similar reasoning. One such supporter claims that because they don’t have eyes or a brain like vertebrates, they must be fair game to the vegan community.

When it comes to sea urchins, no they do not have eyes in the sense that we and other animals have eyes, but “it looks like the entire surface of their bodies are acting as one big eye…” said researcher Sönke Johnsen, a marine biologist at Duke University.” Johnsen is further quoted by the same article saying, “We think of animals that have a head with centralized nervous systems and all their sense organs on top as being the ones capable of sophisticated behavior, but we’re finding more and more some animals can do pretty complex behaviors using a completely different style.” (Choi 2009)

Blevins & Johnsen (2010) stated that their research study is the “first demonstration of spatial vision in an echinoderm sheds further light on the complex optical structures and photobehaviors found in this phylum.”

“It appears that sea urchins may use the whole surface of their bodies as a compound eye, and the animals’ spines may shield their bodies from light coming from wide angles to enable them to pick out relatively fine visual detail….Some of the animals may interpret the object as a predator and flee, while others identify it as shelter and head towards it. What is more surprising is that the urchins’ vision is as good as Nautilus and horseshoe crab vision, which is quite impressive for an echinoid that has turned its whole body into an eye.”
(Knight 2010)

And on the claim that they “do not have centralized nervous systems” as basis to decide it’s ok to eat them, the fact remains that sea urchins and all echinoderms, including sea urchins, have nervous systems:

Johnsen stated that, “Although sea urchins don’t have brains, “it could be their entire nervous system more or less acts as a brain,” Johnsen said. “In our case, we vertebrates have nervous systems that are more or less controlled by a central brain, but sea urchins have a pretty diffuse nerve net, where no region looks like a central processing unit as far as we can tell.” (Choi 2009)

“The adult echinoid nervous system is comprised of 5 radial nerve cords, which are joined at their base by commissures that form a ring surrounding the mouth (Cobb, 1970 Cavey and Markel, 1994)… Tube feet, spines and pedicellariae have ganglia and a complement of sensory and motor neurons…The arrangement of the nervous system in echinoderms is a feature that distinguishes them from other deuterostomes (chordates and hemichordates). Echinoderm nervous systems are dispersed, but they are not a simple nerve net. The adult is not cephalized, yet the radial nerves are segmentally organized (Burke et al 2006).”

Most importantly, Johnsen also states that, “We think of animals that have a head with centralized nervous systems and all their sense organs on top as being the ones capable of sophisticated behavior, but we’re finding more and more some animals can do pretty complex behaviors using a completely different style…In the beginning, people built robots like they would humans, with powerful central processing units, complex sensors and fairly complex rules for doing things…Now they’re finding it might be a lot better with a distributed system with many little processors and simpler sensors and simple rules, which end up creating fairly complicated behaviors as emergent properties, just as how a flock of birds can make intricate patterns without any one bird choosing these patterns.” (Choi 2009)

Thus, not having a nervous system with a brain does not mean you are a living plant-like rock creature incapable of experiencing the world. Plants don’t have nervous systems. Echinoderms (and Bivalves) do have nervous systems regardless of how simple one believes them to be.

Pain in Invertebrates

It is important to note that, “the clear distinction that once existed between the terms “pain” and “nociception” has become blurred recently, to the point that many neuroscientists and clinicians no longer make a distinction that is, most accept that nociception is equivalent to pain.” (Sladky 2014)

In his essay examining pain and analgesia in fish and invertebrates, Dr. Sladky, from the University of Wisconsin, asks, “can we recognise pain in fish and invertebrates? Is the perception of pain by a fish or an invertebrate equivalent to that of a mammal? We will never be able to fully and objectively answer these questions, because the animals simply cannot tell us…Could it be that recognition of pain in fish and invertebrates is impeded by our inability to empathise with species that do not convey distress through facial expressions, do not vocalise in response to distress, and are not warm and fuzzy?”

Dr. Sladky states that “our limited understanding of pain and analgesia in fish and invertebrates should not obscure our clinical decisions, and we should err on the side of fish and invertebrate well-being by making the assumption that conditions considered painful in humans and other mammals should be assumed to be potentially painful across all other vertebrate and invertebrate species.”

“Although peripheral nociceptors have not been identified in cephalopods, there are no published reports that anyone has investigated peripheral nociception in cephalopods. On the other hand, nociceptors have been identified in anemones, sea cucumbers, leeches, nematodes, Drosophila, and many other insects (Kavaliers 1988 Tobin & Bargmann 2004 Xu, et al. 2006 Smith & Lewin 2009 Puri & Faulkes 2010)…Many invertebrate species (earthworms, roundworms, molluscs, Drosophila) possess endogenous opioid receptors (Dalton & Widdowson 1989 Tobin & Bargmann 2004). Immunohistochemical staining indicated the presence of endogenous opioid receptors in nematodes (Prior et al. 2007). Mussels possess benzodiazepine and opioid receptors in their nervous systems (Gagne et al. 2010). In addition, there is genetic and physiologic evidence that invertebrates and vertebrates may have similar capacities with respect to pain and analgesia…”(Sladky 2014)

“Pain-associated behaviour of invertebrates has been described in multiple species. In sea anemones, crabs, crayfish, sea slugs, snails, flatworms, crickets, praying mantis and Drosophila, withdrawal responses are observed with thermal and mechanical noxious stimuli…”(Sladky 2014).

The paper by Dr. Sladky is definitely worth the read because it is a nice summary of all the discoveries that have been made about fish and invertebrates with relation to pain. Read it here:

Albeit slowly, science has shown us that invertebrate species are not as simple as we once thought. So I ask, what basis is there for not erring on the side that potentially oysters, and other invertebrates, that have yet to be studied in detail, also have the ability for these mechanisms and behaviors?

Would it not be unethical to apply standards to species that science has yet to fully study or understand?

Would it not be unethical and unfair to apply specific standards to species with completely different body forms that work in completely different ways than we could ever imagine?

Watch the video: Δεν βρίσκω λόγια Νίκος Βέρτης (December 2021).