Jellyfishes – Animals On The Verge Of Exploitation?
In the seemingly endless efforts to expand the human circle of exploitation, jellyfishes seem to be on the radar of many interested parties — even the European Commission is supporting projects attempting to find ways to make use of these animals. A four-year-long research project, for instance, was granted over 6 million euros to investigate how we could use jellyfish in fighting marine microplastic pollution. What’s more, it seems that the globalization of food markets and the new ‘novel foods’ regulatory system in the E.U. may very well function as a green light for stakeholders interested in serving jellyfishes up as food.
Jellyfishes are an incredibly diverse group of animals, ranging widely in terms of size, where adults can be anywhere between millimeters and meters in diameter, and where they live, with different species inhabiting the arctic, the tropics, the deep seas, the shallow coastal waters, and everywhere in between, even freshwater. They also have widely differing appearances: their shapes, colors, and rigidity of their bells and tentacles come in many variations (just google and compare box and Halitrephes jellyfishes). Their hypnotizingly fluid movements, semi-transparent structures, and incredible regenerative capacities of medusae have mesmerized humankind for hundreds of years.
Ones To Exploit?
Should we be concerned, though? Are jellyfish sentient animals? Researchers at Rethink Priorities, an effective altruism-aligned think tank, carried out a literature review in their attempts to estimate just that — more on their methodology for assessing the likelihood of invertebrate sentience across many species was presented in a recent Faunalytics summary. The report suggests that, although the animals exhibit some nociceptive reactions and have a nerve net that allows them to detect different stimuli, they do not have a central nervous system or any other alternative structure capable of centralizing the processing of the perceived information. In fact, the researchers were forced to place the likelihood for jellyfish sentience at low, mainly due to the fact that so many markers, often used to gauge sentience, have never been evaluated in jellyfish.
Specifically, Rethink Priorities gathered data on the moon jellyfish (Aurelia aurita), a species that is relatively widely studied. Out of all features that the researchers normally take into account when estimating the likelihood of sentience in a given animal, the moon jellyfish exhibited “unknown” capacity on 64% of the criteria, highlighting just how little we know about these enigmatic beings. It is noteworthy, however, that out of the data that we do have – most were offered negative evidence for the sentience of these animals in one way or another. It is also important to note that jellyfishes differ greatly in terms of their physiology across the different classes and species of cnidarians, too. Think, for instance, of the seeing, active box jellyfish and stalked jellyfishes who are sessile and do not possess the means to acquire any visual information. Similar to the case of some of the low trophic animals that we have recently covered, jellyfishes possess a simple radial neural network with action potentials, synaptic transmission, neuropeptides, and neurotransmitters. At first glance, it seems that the movement of these animals is not organized. Further arguments behind the low perceived likelihood for sentience include the fact that there is no evidence of jellyfish perceiving pain, and the simplicity of their behavioral repertoire.
Some evidence, however, argues for the contrary, suggesting that jellyfishes behaviors, ranging from environmentally-induced directional swimming to wall avoidance and aggregation forming, are complex. Furthermore, one long-time jellyfish observer adds in a 2011 review that despite being entirely different from that of other animals, the nervous system of a jellyfish must include a brain of sorts, for the adaptive behaviors these animals engage in play a critical role in their survival. Scientists urge for more research so that we can understand how their relatively simple neural network structures allows them to perform such a diverse range of complex, organized, and directional (think, for example, of moving individual tentacles to deliver prey to the mouth) functions. In a 2014 research article, researchers also showed that jellyfish are capable of preferential decision-making, choosing to stay within a safe salinity level despite being touched multiple times. On the other hand, the animals did not seem to ingest items in an overly strategic manner – intaking animal, vegetal and woody matter with equal fervor.
Meanwhile, other research highlights that box jellyfishes are the ‘simplest’ animals in whom sleep states have been observed. This has been recently confirmed, when researchers found that Cassiopeia jellyfishes do sleep, and that their quiescence is regulated both by homeostatic and circadian rhythms. Actually, box jellyfishes differ greatly from their fellow cnidarians, a phylum that also spans corals and sea anemones, in that they possess a specialized visual system, one comprised of 24 eyes, that generates blurred images which aid in object avoidance. The cubozoans are active predators – unlike any other jellyfish, they approach prey in an organized, fish-like manner. While on the topic of prey and avoidance, other researchers have reported that jellyfishes are known to exhibit anti-predatory behavior by escaping attackers and employing stinging cells to defend themselves.
Evidence is also plentiful of jellyfishes forming large groups and aggregating in vast numbers. But is this due to chance, environmental pressures, or is it a manifestation of sociality among the animals? Observations suggest that such jellyfish encounters should not be automatically written off, but treated as a form of active group formation. However, researchers have not been able explain how the animals seek each other out at great depths and how the group adapts when more and more individuals approach. One thing’s certain, though, jellyfishes can indeed find one another and team up. One particular species of box jellyfishes, Carybdea sivickis, has also been observed to exhibit courtship behavior, where the males engage in rituals of selectively approaching females with the brightest and most visible spots, grabbing them with their tentacles and mating with the chosen ones.
Although very few studies exist on the cognitive capacities of jellyfishes, one paper, put forth back in 1994, does suggest that these animals exhibit habituation. Essentially, this form of learning relates to organisms minimizing their responses to a frequently repeated stimulus. In this particular study, the researchers showed that jellyfish can get used to being touched. They also ruled out alternative explanations for such behavior such as fatigue or sensory adaptation by including a new stimulus and recording dishabituation.
Jellyfishes On Our Plates
Meanwhile, researchers have tried to define the attitudes of consumers towards jellyfishes as food, such as in one Italian study. The study included gathering survey answers from 1,445 Italians, where the questions had been aimed at gauging their views on consuming jellyfish and corresponding socio-demographic and other individual traits. The research indicates that males, younger people, correspondents who travel abroad often, and island dwellers were, on average, more likely to engage in future jellyfish eating. On the contrary, people who exhibit food neophobia and sensitivity to disgust were much less inclined to adopt new cooking habits that include eating jellyfishes. In the latter case, as has been shown numerous times in similar studies on consuming insects, people express reluctance when they have to make a meal using the entire organism versus, say, jellyfish derivatives or pieces.
Based on nutritional information provided by other research, it seems that due to the very low caloric density of the animals (being made up of more than 97 % water) it would take eating hundreds of dried jellyfishes just to match the number of calories of a single Beyond Meat burger. The potential implications for the number of individual jellyfishes to be killed for food are thus immense.
Despite the growing interest in using jellyfishes for food, there are no standardized handling, processing recommendations, or guidelines. Furthermore, researchers argue that there are no specific food safety and quality parameters prepared at the time being. A recent study looked into several jellyfish processing methods and found that the tested jellyfish samples did not contain pathogens, despite exhibiting a limited presence of Staphylococcus bacteria, and the animals were not deemed a source of severe microbiological hazard for humans. However, the researchers did highlight the importance of dissecting the animals, eliminating gastric contents, and washing the body parts thoroughly to ensure high safety levels. Finally, a need for new tools for safety and quality assessment was highlighted, one that should be met before introducing such novel foods commercially.
Another group of Italian researchers sought to test a high-temperature processing method, in an attempt to see whether it is possible to achieve much faster production. The authors suggested that technology-driven processing protocols must be developed for jellyfish products to meet food safety rules. The researchers also claim that new techniques could help in overcoming neophobia towards jellyfish as a food and to kick start a new culinary tradition in Europe. The proposed processing method was shown not to reduce the radical scavenging (antioxidant) properties of the studied jellyfish. However, the three tested Mediterranean jellyfish species were not equally compatible with the proposed methods, mainly concerning varying efficacies in retaining protein and phenolic contents.
Jellyfish Troubles In The Wild
Jellyfish “blooms” are on the rise, where thousands of individuals are observed in groups. Some researchers suggest that overfishing in the oceans is to be blamed – with many of our target fishes being notorious predators of jellyfishes. More and more efforts are now directed at tracking jellyfish populations in attempts to better understand why such formations are much more frequent nowadays and what effect this may have on an ecosystem level. A past summary on Faunalytics reveals that worldwide populations of jellyfishes are growing. Researchers even resorted to making use of citizen science, to record sightings of jellyfishes via a database called Jellywatch, as besides interference with the tourism industry, such shifts in fauna may lead to marine biodiversity losses, too.
Obviously, with more and more jellyfishes out in our oceans and seas, and especially not too far out offshore, more of these animals are bound to fall victim to by-catch. A team of U.S. researchers noted that catching large jellyfish in fishing nets was rare before the 70s. Since 2007, on the other hand, it has not been uncommon to capture three times as many jellyfish in weight than that of commercial, target fishes. The researchers highlight how serious the effects of fishing unsustainably can be on a given ecosystem, mainly via reducing the stability of the natural system and its resilience to external pressures, in this case – our unsatiable appetites. Living in the vicinity of people may pose yet another danger for jellyfishes – noise. In a 2016 study, researchers from Spain and France highlighted that despite ever-rising, albeit poorly regulated, levels of anthropogenic noise in marine environments, we are still unsure what effect noise pollution has on soft-bodied aquatic animals such as cephalopods and cnidarians. Via microscopy, the researchers were able to record that physical damage to bodily jellyfish tissues is induced by acoustic trauma. Some jellyfishes are observed to sense distances and by doing so, avoid stranding. This is believed to be possible due to sensitivity to water pressure changes or water turbulence. It makes sense that this sensory capacity of theirs has a safe threshold, too, one that’s at risk in noisy waters.
With all of this in mind, it is clear that we might be going down a bad road by allowing the commercialization of jellyfish capture or farming for human consumption. There are simply too many question marks — we do not understand the animals enough to be certain of how to ensure their wellbeing in a farming context, and as animal advocates, this is still a potential industry we can prevent from coalescing.
Animal advocates should push for evidence when exposed to the question of whether humans should be eating or otherwise exploiting jellyfishes. Do they feel pain? Perhaps not in the way that we think of it. Is it clear that they want to survive? Absolutely. Do we know what it is like to be a jellyfish or whether they can suffer? Not yet. It might be very difficult to inspire compassion for beings so different from us, as jellyfishes are. However, given the vast number of individual animals that would be killed, this serves as a classic example of the need for the precautionary principle. Absence of evidence is not evidence of absence, after all.