On the Consumption of Bivalves

David Cascio

What is the purpose of ethical veganism if not to avoid causing pain to other sentient life forms and/or to end cruel and polluting factory farms? Bearing in mind a few things:

— Not all foods with a high environmental or ethical cost are animal products (e.g. poorly sourced cocoa, some palm oil)

— Some animal products are not always avoided due to ease of access (e.g. bone char sugar)

— The definition of veganism means attempting to not exploit or kill animals as much as practical and possible

What happens when you find an animal that is not sentient, i.e. has a rudimentary nervous system with no centrality, no capability of having thoughts, has less secondary death than crop harvesting, farming them is actually beneficial to the environment, and when sourced properly are a healthy and nutrient-dense food? A common attitude is that if the situation is antagonist to the definition of veganism, e.g. consuming an animal product, whether or not it is actually better for sentient life and the environment does not matter; vegans still need to avoid its consumption to preserve the purity of the vegan label. If veganism is aimed at promoting the greater good in place of causing suffering, how does this make sense? Basic biology tells us the animal kingdom is full of different forms of life, ranging from the floating, unaware sponges with no nervous system and sessile corals all the way to high apes like humans. There are mollusks that problem solve and display complex behavior, such as octopuses, while their cousins, bivalves, have no behavior other than reflexes.

Nervous System
 Bivalves have no central nervous system. They cannot use endogenous opiates or opiate receptors to inhibit pain, as they have no brain or way to process sensory input, but only the equipment to crudely react to it. They do not have the equipment to experience pain, consciousness, or awareness. In respect to morphine studies that has shown that the mussel species Mytilus edulis has μ opioid peptide receptors. The question is, what is the entire purpose of μ opioid peptides? Why would an organism without the equipment to process pain need opioids? The answer is likely the fact that μ opioid peptides are also used to suppress unnecessary biological functions in response to stress, so they are very likely present as a neurotransmitter to alert the body to direct its focus away from the nonessentials and regulate its cardiovascular system. [1, 2, 3]

This is analogous to plants, as when plants are damaged, they detect it and respond by emitting ROS and starting up calcification and phosphorylation processes. A good way to think of bivalves is to relate it to if you were to hit a minimally decayed human cadaver with an intact spinal cord in the knee with a reflex hammer. If the body isn’t too decayed, the knee will reflex and jerk forward, because of localized stimuli processing. This obviously does not cause any pain to the cadaver, because the brain is disconnected from the nervous systems. Pain is an experience requiring certain biological assets that plants, bivalves, sponges, etc. simply lack. Bivalves have methods of sensing damage (similar to our bodies), but are not sentient, thus do not feel pain, analogous to plants. [4, 5, 6] Here is a diagram of the typical base anatomy of a bivalve borrowed from the University of Vermont (link is in the description below):


In order for an organism to have consciousness, there must be a re-entrant circuit connecting perception and association, like vertebrates’ thalamocortical network. Invertebrate consciousness may exist in some species if they have a mediated cortex connection. In vertebrates, there is a requirement for fluid and regulated communication from the thalamus to at least a basal vertebrate telencephalon to have conscious reactions to stimuli.
 Consciousness must involve a neurobiological function allowing organisms to bind and distribute information about changes in real-time. For example, for an organism to be able to see a predator swimming toward it and for it to then consciously respond to it before it is eaten, rather than just reflex away in a knee-jerk reaction, the organism needs a dynamic thalamocortical system that ensures neurons are actively maintaining a fluid awareness of a real-time stream of information. It’s not incredibly simple for that to happen — it requires a great deal of synchronization and neurological complexity throughout the central nervous system so that each involved part of the brain selects and correlates the same fractions of our neural oscillations in different ways at the same time in ways that logically sync and produce the desired results. [7]

For example, when we choose to use a section of our conscious mind to remember learning to write when we were in school as small children, we might be thinking of the feeling of the pencil in our hands, the smell of pencil erasers, the process of moving our hands in the same pattern as the text seen with our eyes, the sound of graphite on paper, our teacher’s voice and face, maybe a taste if we were a pencil chewer, and also that feeling of focusing and attempting to learn material. As higher mammals, we also have the ability to remember it subjectively. We remember and relate memories to other memories or to our present situation. So much fragile processing that even our adult, fully-formed nervous systems get confused over regularly.

All of those aspects are remembered differently, with different pieces coming from various combinations of parts of central nervous system. Without our entire nervous system centralized with a fully connected thalamocortical system to translate and integrate this massive and continuous ocean of partially oscillating, dissimilar electricity, the disconnected bits and pieces are not capable of communicating with each other or being interpreted as thought.
 Consider this — what structure would be needed to maintain the neurons responsible for mediating active and perpetual consciousness in order to maintain awareness without the input of any outside neuron-activating stimuli? Which structure would be responsible for the required high level of communication throughout the central nervous system so that each involved part of the brain selects and correlates the same fractions of our neural oscillations in different ways at the same time in ways that logically sync and produce our mental state?
 If the answer is that external stimuli-induced consciousness is all that is necessary for consciousness to naturally exist, this would be a less accepted theory of consciousness without much supporting evidence. It’s often considered not possible for a few reasons. One reason is that it relies on 1–1 relay of sensory information, which fails to offer an explanation for mass, associative, and intentional connectivity in models. Another is that changes cannot be recognized without being aware of how things were prior to the change in order to have a relative state of reality in which to compare. Albert Einstein summed this up better than I can:
 “Space and time are modes in which we think, not conditions in which we exist.”
 Without our central nervous system’s temporal processing capabilities, we would not perceive time. Time is responsible for our fourth dimensional perception of our world. According to String Theory, there are at least 6 dimensions our brains can’t directly perceive, so there is still some room for improvement!

If a direct stimulus activating a neuron cluster somehow temporarily wakes up an underlying network of consciousness, followed by the organism immediately falling back into a sleeping state when neural activation subsides, life would just be a series of meaningless jump-scares that the organism could never relate to (or even recall) previous jump scares, or simply understand. Some groups have proposed possible forms of consciousness wholly comprised of a series of spontaneous and brief awakenings directly derived from intermittent stimuli, but these still require a controller to facilitate the awakenings. Some have suggested the pulvinar nuclei in the thalamus. [8, 9, 10, 11]

There are thousands of papers on this topic, but I’ll just share some details about a few impactful ones. It’s a very interesting story of scientific development that primarily kicked off in the 1980s, although philosophy and science about the human consciousness obviously go back to ancient times.

An early major paper was by a German scientist, Christoph von der Malsburg, who published a paper “The Correlation Theory of Brain Function” in 1981, realizing that for consciousness to exist, the entire nervous system needs to have very complex, mediated communication, calling brain function “a tangle of interrelated problems — none of which can be solved, or even be precisely formulated, on its own. In this situation a concept of global brain organization is needed…” [12]

In 1994, another group of scientists published a paper providing some of the first evidence supporting “the view that 40-Hz (oscillating gamma band) activity not only relates to primary sensory processing, but also could reflect the temporal binding underlying cognition.” This potentially incomplete view is based on the thalamocortical network. [13] A year later, another paper was published that “traces in some detail the empirical evidence concerning the gamma binding process and presents some implications for the constitution of a unified cognitive-mental space.” [14] This further illustrates that a requirement for consciousness is highly mediated gamma band oscillations.

Many small pieces of the puzzle continued falling into place, while simultaneously making the puzzle more complex. An example was in 2001, a publication discovered a missing link — the unity factor: the N-methyl-D-aspartate channel. This channel is an ion activated signal transduction pathway geared towards increasing information dispersal speed to facilitate the strict coherence between the sensing of perceived stimuli and the signal to your associative cortex to determine the accurate physiological and psychological responses. [15]

Francis Crick (cofounder of the double helical structure of DNA) began speculating in 1990 that gamma wave oscillations through the thalamocortical network were responsible for consciousness. Then in 2004, he and Christof Koch cited many other works and published a summary as one of the first major collective explanations of prevalent observations — a 10 point outline full of educated speculations about how everything is connected to produce consciousness. [16, 17, 18]

Perhaps the biggest player in this research was Gerald Edelman. He published several papers and books on the topic over the last 30 years, integrating and inventing new ideas and theories along the way to craft what is currently the model of linked and integrated consciousness with the most supporting neurobiological evidence. He coined the terms “Primary” and “Secondary” consciousness to discern between states of being acutely aware of your surroundings while actively associating input with long term memories (secondary) and just being persistently aware of your present state, both physically and emotionally (primary). Animals with just primary consciousness have long-term memory, but lack narrative. This means they can learn, but they only remember what they learn when they are in the same situation they were in when they learned it. This concept was termed “Remembered Present”. Animals with primary and secondary consciousness, like great apes, are capable of actively building mental narratives. In the case of humans, this means enabling the development of languages, art, and science. This is certainly not limited to great apes. Evolutionary science has proposed that secondary consciousness evolved around the times reptiles diverged into mammals and birds. Starting in the basal species of these classes, a flood of new re-entrant connections quickly began developing in the new brain systems, which allowed stronger communication between the posterior brain responsible for perception and the frontal brain responsible for value-category memory. Secondary consciousness is essentially being able to selectively remember and correlate things, so there is a very large area for variability. This is to say that “primary” and “secondary” are not binary labels, but are in essence two separately binned spectrums. [19, 20, 21, 22]

Scientists are even able to use these theories to discover new explanations for long-evasive medical issues. For example, last year after hints from several publications, it was discovered that chronic pain conditions can be observed at the thalamocortical network level as inconsistent, altered connectivity resulting in improper signal dispersal, showing that chronic pain is a network connectivity disorder. [23]

This is not to say through all of this research we have a perfect model with all of the answers. There are still aspects that are debated and evolving. For example, some scientists believe the oscillation synchrony is not directly responsible for consciousness, only directly related in the sense that it is possible the oscillations are utilized to direct blood flow to active areas of our nervous system. This is not widely accepted and has faced criticism, but even this idea does not deny the required anatomy, only how said anatomy facilitates. [24] Other scientists are still working to develop more robust models and to clarify whether a brainstem, in addition to a thalamocortical complex, is a requirement for consciousness. [25, 26, 27] 
 The relevance here is that modern neuroscience research is settled on many of the vital requirements for even minimal consciousness. At this point, we’re decades into determining the minutia of why, while merely fine-tuning the basics of how. At the bare minimum, it is essential for the thalamus to be connected with the cortex (or something analogous to this). [28] This thalamocortical basis of consciousness is also a way used to explain the boundaries of fetal consciousness (i.e. the network doesn’t start forming until about 24 weeks into gestation and doesn’t finish connecting until around 29 weeks, after reflexes and hormonal stress responses). [29]

 Bivalves were one of the first animal classes to evolve on Earth over 500 million years ago. It is not plausible that they could have sentient ancestors, since their lineage predates the brain. Their ancestors had a similar pair of ganglia relative to what they have now. They appear to have no ancestors more complex or intelligent than themselves. The basalmost bilaterians were probably simple paraphyletic acoels, which showed up in fossil records not long after the basalmost animal, the sea sponge, which has no nerve cells and is entirely sessile. Ancestral acoels had no central nervous system either. In fact, their nervous system was arguably simpler than some bivalves. Their ancestors had a few nerve cords connected with simple commissures and an intraepithelial nerve net without any submuscular nervous structures. It’s worth noting my reasoning that motility is not a good indicator of sentience applies here as well. I say this to point out that there is nothing in the ancestry of bivalves indicative of there being a potential remnant of consciousness. Bivalves have no analogous hardware, much less an entire analogous system. [30, 31, 32]

While the bivalve neural network is connected, it lacks neurons that need to be constantly triggered or continuously communicating with other types of neurons. Their network is heavily reliant on action potentials independently being reached to trigger pre-set biological processes. While sensory neurons may be constantly stimulated from external factors, directing sensory information into a reflex via neural pathways directly towards physiological responses is not the same as being aware of the sensory information. Awareness would require constant neural activity that translates sensory neural activity into more than just a reflex. There would need to be something like a thalamus to integrate the information into another structure capable of interpreting it into subjectivity. When our stimulated-related cortical oscillations slow down, we fall asleep and lose awareness, but our bodies continue to function normally. If this wasn’t true, general anesthesia wouldn’t put us to sleep and surgery would be much more unpleasant. So again, the isolated process of nerves firing does not create consciousness alone. Like my reflex hammer to a corpse’s knee example — the corpse is not sentient, even though many of the neurons in its leg and potentially up to its spinal cord are firing.

While some adult bivalve species are sessile, all bivalves will recoil slightly when touched, due to their two pairs of nerve cords and three ganglia connected via simple commissures that allow the entire organism to react to localized stimuli. These simple networks are essentially limited to providing physical reflex and assistance in autonomic processes, as they are not hooked up to a central processing unit. [33] Bivalves with simple eyes or photoreceptor cells also reflex to light level shifts translated to detect and avoid moving objects, chemoreception, and response to physical stimuli, similar to a human pupil dilating due to a shifting light levels which trigger involuntary iris nerve innervation from the parasympathetic nervous system, rather than out of a conscious and aware decision (like the reflex hammer example). Almost all living organisms can detect damage, reflex in some way, and proceed to heal, with sentience having nothing to do with it. [34, 35, 36]
 This is also similar to the Venus flytrap, which detects stimuli and clamps down in response. If the argument against eating bivalves is that the conversation is fundamentally flawed because we shouldn’t ascribe human ideas of sentience to nonhuman animals, that argument would need to extend at least to the plants that exhibit epinasty, hyponasty, nyctinasty, seismonasty, and thigmonasty and the fungi and algae that have zoospore stages as they are all, in a sense, crudely aware of external factors. [37] The biological mechanisms are different, but the involuntary reflex aspect is biologically analogous. This same sort of reaction allows some bivalves to be able to hide and crudely navigate, but there is still no sentience.


To use a corporate analogy, let’s say you run a major American corporation called “Sensory Reception” where your product is hypoallergenic soap. You have many respective soap products — liquid, bar, gel, rock, and foam (photoreception, thermoreception, mechanoreception, chemoreception, and nociception). To make these products, you need a specific team of employees for each soap type. You need specific marketing teams to determine the best ways and locations to sell the products (one team per afferent sensory neuron: photoreceptors, thermoreceptors, mechanoreceptors, chemoreceptors, and nociceptors). You need specific sales teams to ensure sales goals are met by relaying information between accounting and marketing (sales team: interneurons). You need specific accounting teams to make changes to the company strategy based on the information they get from sales, whether through expanding, shrinking, or simply changing (efferent neurons that communicate directly with junctions, such as a motor neuron directing a muscle to move through a neuromuscular junction). Since how well the company is doing financially effects every project, the accounting teams for each project communicate regularly via Skype in case one project’s budget effects any/all other projects’ budgets. (Skype: nerve fibers like commissures, so if a certain threshold is reached, nerve innervation might cause an oyster to both flinch its soft body and also activate other efferent nerves to close its shell).

So you’ve got this simple, but very successful, company (a closed loop, reflex-based nervous system). You’re so successful, you’ve decided to branch out and try to take over the entire toiletry business on a global scale. You set your sights on a Chinese company called “Subjectivity” that makes soap-related gadgets (liquid dispensers, bar soap dishes, gel dispensers, rock trays, and foam dispensers):(Postcentral gyrus, gustatory cortex, olfactory cortex, visual cortex, auditory cortex). Each of these gadgets has a team similar to the soaps, with various pathways and types of neurons.

So, you plan to buy this company with the goal of creating a new, highly connected and advanced organization all in one building (an organism). There’s just one problem. Because you want the related projects to essentially become one project (i.e. consolidating the 10 projects into just 5) and you want everyone on the consolidated projects to work hand-in-hand, they need to be able to speak with each other, but none of the Americans know Chinese and none of the Chinese know English!

To take care of this, you realize you need to hire skilled specific teams of interpreters for each project, because the interpreters must be able to both translate back and forth between your employees and understand the product-specifics related to their project to catch the nuances (these are the various nuclei of the thalamus; there are nuclei for each reception). These translators are responsible for sentience, not because sentience is located in them or because the thalamus is all that is needed for consciousness, but because they are the communication point between two very different systems. This communication point manifests itself as our conscious awareness.

Bivalves have one company (sensory reception) that all speaks the same language — that’s it. They do not have the highly specialized equipment, connected or disconnected, in the first place to experience sentience.

Sustainability and Nutrition

In regards to sustainability, bivalve farming (not wild caught, as this can damage the ocean floor and have detrimental effects) cannot only have incredibly low carbon footprints, but when farmed sustainably via commonly used methods, there is substantially less secondary sentient death associated with them relative to plant harvesting methods, regardless of whether you include insects, amphibians, and small reptiles or only include mammals and birds. With roping methods where the bivalves are grown vertically underwater, the farming bypasses the secondary animal death involved in crop harvesting and requires significantly less land than soy and most other crops while protecting the ocean floor and other ocean life. Veganism reduces harvesting death significantly already as it requires 60–80% less cropland compared to a standard western diet that includes meat, but it does not come close to eliminating it. Oyster and mussel farms are even used by some non-profit and for-profit companies alike to filter bays and improve the surrounding water quality. According to nonprofits and several scientific institutions like Yale, harvesting them can actually be beneficial for the environment. I say none of this to derail veganism, because it is one of the most thoughtful mainstream diets, but simply to point out that making a positive difference may occasionally not be within the current definition of veganism. [38, 39, 40, 41, 42]

The health effects of bivalves are also pretty settled. Bivalves are high in B12, iron, calcium, essential amino acids, omega-3 fatty acids, potassium, and magnesium. They do contain some cholesterol and fat, which would need to be monitored if eating them, but they are relatively low in heavy metals and other toxic substances compared to some other foods and sea life, if sourced properly. Bivalves are very efficient filter feeders that focus on transforming the waste, rather than integrating it directly. To be distributed, they must fall below certain levels of pollution, just like tap water and food items sold in stores in many countries. [43] It’s worth mentioning that avoiding all amounts of all heavy metals would mean no longer breathing, eating, or drinking — it is the dose that makes the poison. Some areas certainly have more polluted water and thus more polluted sea life, but that also applies to sea plants according to recent research. In fact, some research points towards sea plants, like algae, as being a major factor in why some fish contain high levels of mercury, as the sea plants absorb metals like mercury and are then eaten, thus introducing more of the metal into the food web. [44, 45]


With all of this information about bivalves considered, I’ve argued that it is a fundamentally unjustifiable and counterproductive position to hold that eating bivalves should be categorically restricted in a diet based on morality, health, or environmental impact. Bivalves are no worse for the environment or collective sentience than harvesting and processing vegan foods, like wheat, strawberries, supplemented yeast, or fortified milk alternatives. I am not trying to guilt vegans into eating bivalves, but merely pointing out that attacking their consumption is counterproductive. The purpose of veganism to me is to reduce pain and environmental harm to the fullest extent possible, not to live a life devoid of causing animal death, because that is impossible. Causing less harm may sometimes include adopting practices that do not fit into the vegan definition, but diets based on ethics are not like religions with steadfast sets of black and white commandments that are sometimes too generic to apply to an entire world full of so many shades of grey, even if veganism itself is sometimes treated that way.

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Written by David Cascio for The Animalist

On the same topic, also at The Animalist: